FISH RESTORATION PROGRAM PILOT STUDY PHASE I: RESULTS … · the primary goal was to determine which methods were feasible for use in shallow water. A more statistically rigorous

FISHRESTORATIONPROGRAM

PILOTSTUDYPHASEI:RESULTSFROM2015GEAR

METHODOLOGYTRIALSINTHENORTHDELTA

Dave Contreras, Rosemary Hartman, Stacy Sherman, Alison Furler and Alice Low

Fish Restoration Program Monitoring Team California Department of Fish and Wildlife

Stockton, California

FINAL REPORT May 24, 2016

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Executive Summary The Fish Restoration Program Monitoring Team was tasked with developing monitoring plans for tidal

wetland restoration sites being built pursuant to requirements in the 2008/2009 Biological Opinions for

Delta water project operations. We were also tasked with making recommendations to be included in a

generalized monitoring framework for tidal wetlands in the Sacramento-San Joaquin Delta and Suisun

Marsh. Because there are no established methods for monitoring fish or macroinvertebrates in tidal

wetlands in this region, we initiated a pilot study to test multiple methods and determine which to

recommend for inclusion in long-term monitoring programs. In Phase I (conducted July-October 2015),

the primary goal was to determine which methods were feasible for use in shallow water. A more

statistically rigorous comparison of the most successful methods from Phase I is taking place in Phase II

(January-June 2016).

Macroinvertebrates To sample benthic invertebrates, we compared 10cm PVC cores to 15x15 cm ponar grabs and a benthic

trawl. The benthic trawl collected a higher catch of fish food organisms, but a lower catch of benthic

infauna. PVC cores could only be used in water depth of 1m or less, but were logistically easier than

ponar grabs. All three methods will be repeated in Phase II.

In emergent vegetation, we compared three passive collectors: Hester-Dendy disk sets, mesh scrubbers,

and leaf-packs with two active methods: throw traps and sweep nets. We found the three artificial

substrates and the sweep nets to have similar catches, though sweep net samples were much faster and

easier to collect. Throw traps were logistically difficult and had low catch of fish food invertebrates. Leaf

packs and sweep nets will be repeated in a wider variety of habitats in Phase II.

In submerged vegetation, we compared a Marklund sampler to a sweep net. We found the sweep net

had a higher catch per unit effort and a higher coefficient of variation in catch, but similar species

richness and proportion of fish food invertebrates. Sweep nets will be repeated in Phase II and

compared to leaf packs placed in submerged vegetation.

In floating vegetation, we only used one sampler, a d-frame dip net. This method was successful in

collecting vegetation and associated invertebrates, but had a high coefficient of variation. This method

will be repeated in Phase II and will be compared to leaf packs placed in floating vegetation.

For surface fallout/emerging insects, we compared a neuston tow to fallout traps, and found the

neuston tow collected a much higher catch of invertebrates and much higher species richness in a much

shorter time. Neuston tows will be repeated in Phase II.

Fish To sample larval fish, we compared oblique trawls to light traps. Both methods were successful in

catching some larval fish, but logistical difficulties and the time of year made larval catch relatively low.

Light traps will not be repeated in Phase II due to difficulties estimating volume of water sampled. The

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tow schedule for oblique trawls will be refined in Phase II and oblique larval trawls will be compared to

surface trawls.

To sample fish in shallow beaches, we compared the USFWS’s Liberty Island beach seines to a lampara

net hauled as a beach seine. Both were determined to be logistically feasible, though a smaller lampara

net is recommended. The lampara net has the benefit of being usable in areas without beaches. Both

methods will be compared more rigorously in Phase II.

To sample littoral habitats, we compared electrofishing, gill nets, and fyke nets. We discovered some

difficulties in anchoring fyke nets in tidal channels, and further difficulties deploying gill nets in

vegetated habitat. Electrofishing had the highest catch and fewest logistical difficulties, but has the

highest equipment costs and salinity constraints. We will repeat all three methods in Phase II to work

out the logistical difficulties with fyke nets and gill nets.

To sample open-water habitat, we compared the UC Davis otter trawl to a Kodiak trawl and a lampara

net. All three methods were feasible, though the Kodiak trawl will require further adjustments and will

be limited in types of habitat it can sample. We will repeat all three methods in Phase II for a more

rigorous comparison.

We also tested cast nets in a variety of habitats. While their catch was generally low, effort required was

very low, allowing many samples in a short period of time. We will continue use of cast nets in Phase II,

but use nets with lighter weights, bigger mesh size, and smaller radius to improve sampling consistency.

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Contents Executive Summary ....................................................................................................................................... 2

Macroinvertebrates: ................................................................................................................................. 2

Fish ............................................................................................................................................................ 2

Preface .......................................................................................................................................................... 6

Part I: Macroinvertebrates ............................................................................................................................ 7

Introduction .............................................................................................................................................. 8

Study Questions: ................................................................................................................................... 9

Methods: ................................................................................................................................................. 10

Sample Location and Timing ............................................................................................................... 10

Description of habitat types:............................................................................................................... 11

Description of Sampling Methods: ..................................................................................................... 13

Laboratory Methods: .......................................................................................................................... 19

Analysis: .............................................................................................................................................. 21

Comparisons to existing data: ............................................................................................................. 22

Results ..................................................................................................................................................... 22

Feasibility of use .................................................................................................................................. 22

Organisms collected: ........................................................................................................................... 30

Differences between habitat types:.................................................................................................... 32

Differences between samplers within habitat types .......................................................................... 34

Discussion................................................................................................................................................ 39

References: ............................................................................................................................................. 43

Part II: Fish .................................................................................................................................................. 47

Introduction ............................................................................................................................................ 48

Larval Fish Sampling Questions: .......................................................................................................... 48

Juvenile Fish Sampling Questions ....................................................................................................... 48

Methods .................................................................................................................................................. 48

Location and Timing ............................................................................................................................ 48

Larval Fish ............................................................................................................................................ 49

Juvenile/Adult Fish .............................................................................................................................. 51

Results ..................................................................................................................................................... 56

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Larval fish methods ............................................................................................................................. 56

Juvenile and adult fish ........................................................................................................................ 58

Discussion................................................................................................................................................ 63

References .............................................................................................................................................. 66

Acknowledgements ..................................................................................................................................... 66

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Preface The State Water Project (SWP)/Central Valley Project Joint Operations Biological Opinions from the

United States Fish and Wildlife Service (USFWS) and National Marine Fisheries Service (NMFS) and the

SWP Incidental Take Permit for Longfin Smelt from the California Department of Fish and Wildlife

(CDFW), required the California Department of Water Resources (DWR) to restore 8,000 acres of tidal

wetlands in the Sacramento-San Joaquin Delta (Delta) and Suisun Marsh (USFWS 20081; CDFW (formerly

CDFG) 20092; NMFS 20093). Restoration may improve threatened fish’s habitat and food web resources.

In October 2010, CDFW and DWR approved the Fish Restoration Program (FRP) Agreement, which

directed DWR and CDFW to work jointly to implement and monitor the required tidal wetland

restoration (CDFW and DWR, 20124).

Restored tidal wetlands in the upper San Francisco Estuary need well-designed monitoring programs to

monitor benefits to at-risk fish species such as Longfin Smelt, Delta Smelt, and winter- and spring-run

Chinook Salmon. Therefore, the FRP monitoring team formed the IEP Tidal Wetlands Project Work Team

(PWT) to develop a framework for monitoring diverse restoration sites in a standard manner. The PWT

developed conceptual models detailing how at-risk fish may use restored tidal wetland habitat. The

conceptual models provided the pathway to develop hypotheses that led to metrics and sampling

strategies. Many of the sampling strategies were straightforward, and the PWT included existing

standard operating procedures in the framework. However, there was no consensus on the most

desirable methods for monitoring epiphytic and epibenthic macroinvertebrates, or fish in tidal wetlands.

Therefore, the FRP monitoring team undertook a pilot study to test various gears the PWT

recommended.

This report contains the results from Phase I of the pilot study, which collected samples during the

summer and fall of 2015. The major goal of Phase I was to see which methods were logistically feasible

for use in a long-term monitoring program, with feasible methods to be tested further in Phase II.

1United States Fish and Wildlife Service (USFWS) (2008). Formal Endangered Species Act Consultation on the

Proposed Coordinated Operations of the Central Valley Project (CVP) and State Water Project (SWP). C. a. N. R.

United States Fish and Wildlife Service. Sacramento, California, United States Fish and Wildlife Service. 81420-

2008-F-1481-5: 396 pages.

2California Department of Fish and Wildlife (CDFW). (2009). California Endangered Species Act Incidental Take

Permit No. 2081-001-03 on Department of Water Resources California State Water Project Delta Facilities and Operations. Sacramento, CA. 3National Marine Fisheries Service (NMFS) (2009). Biological Opinion and Conference Opinion on the long-term

operations of the Central Valley Project and the State Water Project. Long Beach, California: 844 pages.

4CDWR and CDFW (2012). Fish Restoration Program Agreement Implementation Strategy: Habitat Restoration and

Other Actions for Listed Delta Fish. Sacramento, CA, Department of Water Resources and Department of Fish and

Game in coordination with the US Fish and Wildlife Service and the National Marine Fisheries Service.

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Part I: Macroinvertebrates

By Rosemary Hartman and Alison Furler

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Introduction

In this study, we evaluated methods of sampling macroinvertebrate communities in tidal

wetlands. We focused our effort on taxa that provide food for Endangered Species Act-listed

fishes (Delta Smelt, Longfin Smelt and Chinook Salmon). This is part of an ongoing effort to

recommend standardized monitoring methods for tidal wetland restoration sites across the

Sacramento-San Joaquin Delta and Suisun Marsh. Macroinvertebrates associated with

vegetation and shallow water habitat, such as amphipods and insect larvae, have been

historically under-studied in this system; however, they provide the majority of salmonid diet in

these areas (Merz 2001, Sommer et al. 2001, Maier and Simenstad 2009, Bottom et al. 2011),

and are a component of Delta Smelt diets when smelt occur in areas of high macrophyte

production (Whitley and Bollens 2014). We tested several different macroinvertebrate methods

to find the most effective methods to be used in concert with traditional zooplankton trawls in

future monitoring programs.

The methods analyzed here were all based on recommendations from the IEP Tidal Wetlands

Monitoring Project Work Team (PWT). When asked to recommend sampling methods for

macroinvertebrates in vegetated areas, the PWT developed a long list of potential methods,

most of which could only be used for a specific subset of the community. Many methods that

are used for other monitoring programs prioritize diversity and presence of sensitive species (as

index of biotic integrity) rather than biomass or productivity (i.e. Klemm et al. 1990, Hunt et al

2001). The PWT is primarily interested in differences in production of fish-food invertebrates

over time and between habitats (biomass of taxa that may be consumed by salmon and smelt),

rather than presence of sensitive species, so many methods standardized for IBI studies may

not work well for long-term tidal wetland restoration monitoring.

The PWT Food Web Subteam hypothesized that some form of artificial substrate would provide

a standard method of assessing invertebrate biomass that would be easier to compare between

habitat types and study sites. However, the effectiveness of artificial substrates in attracting

colonists may vary by habitat type (open water, and different types of vegetation), and may be

biased toward certain invertebrate species. The subteam therefore recommended a study to

test whether artificial substrates would reflect the community collected through other

methods. They also recommended the pilot study determine the most effective methods for

collecting highly mobile epibenthic/epiphytic macroinvertebrates that may not colonize or jump

off artificial substrates.

In this study, we have made preliminary tests of several artificial substrates as well as more

active methods of collecting macroinvertebrates. We also made preliminary comparisons

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between these new methods and more established methods to make our new monitoring

program comparable to long-term data sets.

Study Questions:

Q1: Which methods are feasible for inclusion in a long-term study plan?

Q2: How does the colonization of artificial substrates compare to active methods in

collecting a representative sample of the macroinvertebrate community? What kind of

artificial substrate provides the greatest biomass and diversity of organisms important in

fish diets?

Q3: How do benthic cores compare to benthic trawls in quantitatively sampling

epibenthic amphipods?

Q4: How do neuston tows compare to fallout traps for sampling terrestrial and surface

invertebrates?

Q5: How do samples from the oblique mysid trawls and ponar grabs used by long-term

monitoring in channel habitat compare to these newer methods?

Our primary goal was evaluating the feasibility of the methods (Q1). We also attempted to

answer Q2-Q5, but we were limited in our ability to address these questions by low sample size,

and they will be further examined in phase II of the study. We compared several active

methods of invertebrate sampling along with several artificial substrates and traps (passive

methods) to assess each method’s ability to characterize invertebrate biomass and community

composition. The methods with the least effort and cost, and low incidental take of listed fish

species will be included in the second phase of the pilot study in which we will analyze the

performance of all methods in different habitat types with greater statistical power. We will use

the results of both studies to choose a subset of these methods that provide a comparable,

efficient, and representative sample of food production for inclusion in long-term monitoring

plans.

We tested five active methods:

Removal of epiphytic invertebrates from plant harvest as used in (Marklund 2000,

Castellanos and Rozas 2001, Toft et al. 2003, K. Hieb et al, CDFW, unpublished data),

Benthic grabs/cores (Howe et al. 2014)

Oblique mysid tows used in IEP long term monitoring, (Hennessy 2009)

Surface neuston tow (Sommer et al. 2001, Howe et al. 2014), and

Sweep nets (Blocksom and Flotemersch 2005).

We tested four passive methods:

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Hester-Dendy disks (Klemm et al. 1990, Blocksom and Flotemersch 2005),

Leaf packs, as used in (Scatolini and Zedler 1996) (Linskens and Jackson 2013)

Mesh pads (dish scrubber) as used in (Atilla and Fleeger 2000), and

Fallout traps as used in (Gray et al. 2002).

Methods:

Sample Location and Timing

Sampling occurred between July 23 and September 8, 2015, to avoid incidental take of listed

fish species and correspond to peak abundance of insects and amphipods (M. Young, pers.

comm., Howe et al. 2014).

The study was conducted in the Cache Slough complex of the North Delta, mostly within the

northern end of Liberty Island (Fig. 1), because this area contains several tidal wetland

restoration sites, and is important habitat for Delta Smelt. Furthermore, the difficulty accessing

the site made leaving invertebrate samplers there for several weeks safer than in well-travelled

channels. There is also a wider expanse of emergent vegetation than in the fringing marshes

around the sloughs, and previous research during the Breach III study and related surveys have

shown high productivity in the area (Lehman et al 2010, USFWS unpublished data).

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Figure 1. Location of invertebrate sampling. Liberty Island is an existing flooded island with

extensive emergent vegetation in the northern half. Prospect Island is a planned tidal

restoration site where these methods may be used in the future.

Description of habitat types:

Habitat type (water depth and presence of vegetation) impacted how our sampling methods functioned,

so we tested methods in four different habitat types (Figure 2). Not all methods were applied in all

habitats.

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Figure 2: Habitat types and relevant gear types used in each habitat type.

Emergent vegetation: We took emergent vegetation samples in two stands of tules

(Schoenoplectus californicus, and S. acutus), both within 200 meters of each other in the

northern end of Liberty Island (38.29976, -121.68925). Vegetation was 2-3m in height, with 50-

100 stems per m2. Some sago pondweed (Stuckenia pectinata), curly-leaved pondweed

(Potamogeton cripsus), and filamentous algae were also present. All samples were taken within

1m of the tule edge, since vegetation was less dense and easier to sample. This is also the area

where salmonids have been shown to forage most effectively (Simenstad and Cordell 2000).

Water depth varied from 0.5m at low tide to 1.2m at high tide. Substrate was composed of fine

silt throughout the sampling area. Sampling gears tested in this area were: sweep nets, fallout

traps, benthic cores, and artificial substrates (mesh scrubbers, Hester-Dendy disk sets, and leaf

packs). Throw traps were collected in a less dense area of S. californicus and approximately

500m further south of the first site, along the side of the levee where plants were shorter (1.5-

2m in height). Depths ranged from 0.3-1m, and substrate was approximately 50% gravel, 20%

sand, and 30% clay.

Open water and channel: Our open water sampling occurred in Hass Slough, a channel close to

Liberty Island. The center of the channel, where trawling occurred, was free of vegetation;

however, the sides of the channel had extensive patches of SAV and FAV, as well as some

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fringing emergent marsh. Unvegetated regions of the bank were armored with rip-rap.

Sampling gears tested in this habitat were: benthic trawls, neuston trawls, and ponar grabs.

One ponar grab sample was lost during processing.

Floating and Submerged Aquatic Veg (FAV and SAV): SAV sampling took place in a patch of

dense Egeria densa, in Shag Slough just outside the breach of Liberty Island. This was

immediately adjacent to a large patch of dense FAV (Echhornia crassipes), with some Egeria

densa growing in the water beneath. SAV was harvested with a sweep-net and Marklund

sampler. FAV was harvested with a dip net.

Description of Sampling Methods:

For all invertebrate sampling methods, we used 500 micron mesh for nets and sieves to target

macroinvertebrates greater than 0.5mm. All samples were preserved in 70% ethanol dyed with

rose Bengal to aid in sorting invertebrates from substrate.

Throw traps (n=3): For each throw-trap sample, we isolated an area of emergent aquatic

vegetation, (0.3m-1m in depth (d) at low tide) with a 1m2 throw trap made from a metal box

frame covered with mesh on four sides, with an open bottom and top. Throw traps are

commonly used for sampling fish and invertebrate communities in shallow vegetated wetlands

(Turner and Trexler 1997, K. Hieb et al, CDFW unpublished data). Traps were thrown over the

top of the plants and immediately pushed down to trap any invertebrates and small fish in the

vegetation. Two crew members standardized the sample for plant density by counting the

number of stems within the trap and averaging the result. They then removed the plants by

cutting them off above the roots with shears and vigorously shaking all invertebrates off the

stems. They then swept the trap repeatedly with a 30 cm by 25 cm d-frame net until no more

invertebrates were captured. All invertebrates were preserved for later taxonomic ID. Catch per

unit effort was calculated as number of invertebrates (n) per volume of water (V) sampled.

CPUE = n/V

Volume (V) = d*1m2, where d is the depth of water in the trap.

Dip nets (n=6): We harvested floating aquatic vegetation (Eichhornia crassipes) by collecting a

0.25m² sample with a 30 cm by 25 cm d-frame net lifted up from below and severing the

connection to surrounding plant material with shears. We removed all leaves and emergent

material, preserving the roots and associated invertebrates for later taxonomic ID. Upon return

from the field, we removed the invertebrates and dried the roots to a constant weight in order

to calculate number of invertebrates per biomass of root material (mv)

CPUE = n/ mv.

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Marklund Sampler (n=6): We collected submerged aquatic vegetation (Egeria) using a

Marklund sampler (Marklund 2000, as per UC Davis Arc study, M. Young pers comm, and USDA

aquatic weeds lab E. Donely Marineau pers. comm). The sampler is a set of underwater “tongs”,

providing a standard 1.25L volume of aquatic plants (figure 3). We preserved all vegetation

captured in the sampler and associated invertebrates for later ID. Upon return from the field,

we dried the plants to a constant weight in order to calculate number of invertebrates (n) per

biomass of vegetation (mv).

CPUE = n/ mv

Figure 3 Marklund sampler used for harvest of SAV. Sampler built by M. Young, UC Davis.

Sweep Nets (n=12): Sweep nets are a simple, but often effective, way to sample the

invertebrate community. Previous studies found sweep nets captured higher species diversity

than many passive methods, though with higher variability in biomass (Turner and Trexler

1997). We used sweep nets to scrape invertebrates off vegetation in emergent vegetation, and

used it as an alternate method of harvesting plants in SAV. We swept a 30 cm by 25 cm d-

frame net through the water approximately 0.5m above the bottom 5 times (10 seconds of

effort), with each sweep being approximately 1 m in length. In emergent vegetation, we

disturbed the vegetation as much as possible to knock invertebrates off the stems. In

submerged vegetation, we collected all vegetation within the border of the net after the sweep

is completed (Figure 4). We preserved all vegetation and associated invertebrates for later ID.

Vegetation caught in the sweep net was later dried to a constant weight (mv) to standardize the

sample.

CPUE = n/ mv

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Figure 4: R. Hartman using a sweep net to collect submerged vegetation and associated

invertebrates. We sheared off vegetation outside the frame of the net so only vegetation inside

the net is retained.

Artificial substrates: One substrate of each type (leaf pack, Hester-Dendy, and mesh scrubber)

was attached to a 2m line and tied to a float so samplers sat at the surface of the water column.

On July 23rd, two of these lines were attached to a single anchor and six replicate sampling

arrays were set out in emergent vegetation, within 1 m of the tule edge. After 25 days (August

17), we harvested six sets, one from each anchor, by carefully surrounding them with dip net,

and removing the samplers from the buoy. We collected the remaining six sets after two more

weeks (day 42, September 3) to see whether a longer time period provides a greater

abundance or diversity of invertebrates.

Figure 5. A: 14-plate Hester-Dendy disk set. B: round mesh pads (commercial dish scrubbers, i.e. Scotch-Brite Multi-Purpose Plastic Scrubbing Pads) C: Leaf packs constructed of mesh bags and S. acutus dried to a standard weight.

C B A

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Hester-Dendy Samplers (See EPA methods Klemm et al. 1990, n=12): We used round 14-plate

Hester-Dendy disk sets, commonly used for characterization of macroinvertebrate communities

in non-wadable streams and wetland ecosystems, and used experimentally in the Delta (Turner

and Trexler 1997, Atilla and Fleeger 2000, B. Young-Landis, USGS pers. comm, Fig. 5A). Hester-

Dendy disk sets are constructed from 8cm diameter Masonite disks assembled on a central bolt

with spacing varying from 1cm to 3cm. Upon collection, we preserved the sampler for return to

lab. In lab, we removed the disks from the pin and scraped them to remove invertebrates for

identification.

CPUE = n/sampler

Mesh pads (modified from Atilla and Fleeger 2000, n=12): We used round mesh pads

(commercial dish scrubbers, 8cm in diameter by 3cm thick, Fig. 5B) to test a higher surface area

artificial substrate. These are commonly used in studies of intertidal marine invertebrates, and

have been used previously in the Delta (Veldhuizen and Messer 2009 unpublished data). Upon

collection, we preserved the entire mesh pad and disassembled the mesh in lab to remove

invertebrates for identification.

CPUE = n/sampler

Leaf packs (n=12): To provide a standard area of substrate naturally available in the wetland,

we used leaf packs. Leaf packs are commonly used for stream systems, but are also used in

wetland and estuarine systems where there is extensive emergent vegetation ((Linskens and

Jackson 2013), Whitfield 1989, Scatolini and Zedler 1996, Warren et al. 2001, Buschbaum et al

2009, Fig. 5). We harvested healthy tule leaves (Scheonoplectus acutus), from White Slough at

Feather River Drive (37.994825, -121.349907) on June 10, and from Yolo Bypass Wildlife Area

just south of Interstate 80 (38.562028, -121.636072) on July 12th. We dried the leaves to a

constant weight in a drying oven at 60 C. We placed 30g (dry weight) of leaves in a labeled,

plastic mesh bag with 1cm mesh (Figure 4c). Upon collection, we preserved the entire leaf pack

and disassembled it in lab. We dried remaining vegetation to a constant weight to calculate

decomposition rates, and combusted a subsample in a muffle furnace to calculate ash-free-dry-

weight to correct for contamination with sediment (Linskens and Jackson 2013). We calculated

effort as number of invertebrates (n) per gram initial weight of vegetation (mv).

CPUE = n/ mv

Benthic core (n=6): Benthic cores have been used extensively to quantify chironomid and

amphipod populations, as well as infauna in tidal wetlands (Gehrts 2010, Howe et al. 2014,

CDFW unpublished data). While many chironomids and amphipod life stages present in fish

17

diets are pelagic (S. Slater, pers. comm), they also have benthic life stages. We took three

samples in open water at each of the two emergent vegetation sites, approximately 1 m from

the vegetation. For each sample, we used a 20 cm diameter benthic core constructed of PVC

(based on design by B. Wells, DWR, figure 6A). Cores were hand-deployed to a depth of 10 cm.

Each core was washed and sieved on board the boat to remove the sand/mud and preserve any

organic detritus and invertebrates. Two crew members estimated % silt, sand, and gravel in the

field, and averaged the values in the field to describe substrate composition. We calculated

effort as catch per surface area of substrate sampled.

CPUE = n/( π*0.12)

Ponar Grab (n=3): In conjunction with benthic trawling, we used a 15x15 cm (6x6 in) ponar grab

modified for use in hard substrates (as per USFWS Liberty Island Monitoring, L. Smith pers.

comm, figure 6B). The sample was processed as for benthic cores, above. CPUE = n/(0.0232m2)

Figure 6: A) Benthic core made of 4” PVC pipe for use in shallow water (<1.5 meters). B) Ponar

grab for use in water greater than 1.5 meters.

Mysid Nets (benthic tows, n=3): Mysid nets have been used extensively to characterize water

column macrozooplankton such as amphipods and mysids that are large components of fish

diets (Feyrer et al. 2003, Slater and Baxter 2014). We sampled macrozooplankton in the water

column during daylight using a 40cm x 40cm mouth (0.500mm mesh size) mysid net mounted

on a sled (Fig. 7) (similar to EMP methods, Hennessy 2009). A General Oceanics flowmeter

mounted in the net measured sample volume, and we standardized effort by catch per liter of

water sampled. The gear was deployed off the rear of a boat and towed along the bottom at 1-

2 mph for five minutes. After retrieval, the net was rinsed from the outside to wash down the

sample into the cod end. All content collected in a cod end was preserved for later ID.

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CPUE = n/((v2 – v1)*k*0.16m2),

where v2 = end flowmeter reading, v1 = start flowmeter reading, k = flowmeter factory

calibration factor.

Figure 7. Set up of oblique sled for mounting mysid and zooplankton nets.

Neuston tow: Emerging insects and collembolla found at the surface of the water are an

important feature in salmonid diets, and are commonly sampled using neuston tows and drift

nets (Sommer et al. 2001, Howe et al. 2014). The neuston net is a 45cm x 30 cm rectangular

net, 1m long towed along the surface of the water from the side of the boat via a davit (Figure

8). We standardized effort by the distance (d) of the tow multiplied by width of net (0.45m) to

calculate surface area of water sampled. We divided the total catch of the trawl (n) by the

surface area to calculate catch-per-unit-effort. CPUE = n/ (0.45m*d). After retrieval, we

preserved all contents collected in a cod end for later ID.

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Figure 8: Deploying the neuston net off the side of a boat.

Fallout traps: Fallout traps have been used successfully in numerous other studies of salmon

diet (Gray et al. 2002). We constructed fallout traps from plastic tubs of soapy water sitting on

the surface of the wetland. Six 11-L plastic tubs (45cm x 30cm) were zip-tied to PVC posts in the

emergent vegetation and filled with 3L of water with 10ml biodegradable dish soap. We left the

traps for four hours. Invertebrates caught in the tubs were concentrated and preserved for

later ID. We standardized effort by multiplying area of the bin by time to calculate

invertebrates/square meter/hour.

CPUE = n/(0.45m*30m)*4hr

Laboratory Methods:

Subsampling: We identified approximately 400 invertebrates from each sample. If more than

400 invertebrates were present in a sample, or more than six hours were required for

processing, we quantitatively sub-sampled using a 4-grid tray (Figure 9). The sample was

spread out evenly over the tray, then a 4-quadrant divider was placed into the tray and one

quadrant was chosen at random. All organisms in the quadrant were counted and the counts

were multiplied by four to calculate number of organisms in the original sample.

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Figure 9. Subsampling strategy.

Taxonomic effort: Invertebrates were sorted to taxonomic level according to their importance

in fish diets (see Table 1) and the first 20 organisms were measured using an ocular micrometer

from rostrum to telson or longest dimension, similar to methods used by the IEP zooplankton

survey (Hennessy 2009). The methods we used did not target zooplankton (<500 microns),

however any whole organisms that were retained by the 500 micron mesh were counted. This

often included some copepods, cladocera and other invertebrates better characterized by

zooplankton trawls. We have included these in our analyses, but will use other gear types to

target mesozooplankton in our regular monitoring program.

Table 1. Levels of taxonomic resolution recommended for each group of taxa commonly found in invertebrate samples.

Phylum Subphylum Class Order Level of ID

Annelida all all Class

Arthropoda Chelicerata Arachnida all Class

Arthropoda Crustacea Maxillopoda: Copepoda Calanoida Genus

Arthropoda Crustacea Maxillopoda: Copepoda Cyclopoida Genus

Arthropoda Crustacea Maxillopoda: Copepoda Other Order

Arthropoda Crustacea Malacostraca Amphipoda Genus

Arthropoda Crustacea Malacostraca Cumacea Class

Arthropoda Crustacea Malacostraca Decapoda Genus

21

Arthropoda Crustacea Malacostraca Isopoda Genus

Arthropoda Crustacea Malacostraca Mysidae Genus

Arthropoda Crustacea Ostracoda Podocopida Order

Anthropoda Hexapoda Insecta Diptera Family

Anthropoda Hexapoda Insecta other Order

Mollusca Bivalvia All Genus

Mollusca Gastropoda All Order

Nematoda All All Phylum

Platyhelminthes All All Phylum

Analysis:

We analyzed the feasibility of including these methods in a long-term monitoring program by

qualitatively describing the relative time required, cost, requirements for special permits,

temporal and locational sensitivity, comparability with long-term data sets, and size of catch.

We then ranked these criteria on a scale of 1-3, with 1 being “positive” 2 being “neutral”, and 3

being “negative”. If methods were positive in most or all these categories, we included them in

the next phase of testing.

For any samples that were sub-sampled, we expanded the counts by the subsample percentage

to calculate catch of the original sample. Given this value for total catch, we calculated catch-

per-unit effort based on the calculations presented above. We averaged the taxonomic richness

for each sampler type to see if certain samplers collected more taxa than others. We calculated the

coefficient of variation in catch per unit effort and in species richness to see which methods had

the highest variability within habitat types. Because the samplers did not all have the same type

of effort, we only compared CPUE directly for methods that had the same type of effort (ie,

sweep nets and Marklund samplers).

We tested distributional fit of the data to multiple distributions using a Chi-Square goodness-of-

fit test. Because total catch and species richness were both best represented by an over

dispersed Poisson distribution, we tested the effect of sampler type on total catch with a

negative binomial generalized linear model (GLM) using the R package MASS (Ripley et al.

2015). Percent fish diet organisms were best modeled using a binomial distribution, so we used

a generalized mixed model to evaluate the effect of sampler type on percent fish diet

22

organisms with sample ID as a random effect. When the global model was statistically

significant (p<0.05), we used orthogonal contrasts to test pairwise comparisons between

sampler types within specific habitats using the R package multcomp (Hothorn et al. 2016).

To look more broadly for differences in community composition, we used a permutation-based

multivariate analysis of variance (PERMANOVA) using R package vegan (Oksanen et al. 2016), to

compare community composition across habitat types and sampler types.

Comparisons to existing data:

We used published diet analyses for Delta Smelt (Slater and Baxter 2014, Whitley and Bollens

2014) and Chinook Salmon (Duffy et al. 2010, David et al. 2014, David et al. 2016) from the Bay-

Delta Estuary and similar wetland habitats to determine which samplers collected the highest

proportion of invertebrates that are prominent in the diets of fish species of concern. We

designated each taxon as “fish diet” or “not fish diet” and compared % of catch made up of fish

diet invertebrates using a mixed binomial GLM with sample ID as random factor.

IEP Fall Midwater Trawl and Summer Townet survey stations 713, 716, and 721 collect zooplankton from

the Cache Slough region, and the USFWS Liberty Island survey collects zooplankton via surface trawls

from the open water of Liberty Island (L. Smith, unpublished data). Both programs use a 150 micron

mesh zooplankton net to sample open-water, and the Fall Midwater Trawl survey also samples mysids

and amphipods using a 500 micron mesh net (Finstad 2015). Currently, no regular benthic sampling

takes place in the region; however, DWR’s Environmental Monitoring Program takes samples from the

Sacramento River at Rio Vista (Wells 2015), downstream from Liberty Island. Many organisms can be

expected to be similar. They use a 0.052m2 ponar grab to sample the benthic substrates of large, open-

water channels and identify all organisms in the substrate to species (see on-line metadata, Wells, 2015

for full description of methods). We looked at these data qualitatively to see if major differences stood

out, but did not have high enough replication to make statistical comparisons.

Results

Feasibility of use

Assessing the feasibility of these methods in long-term monitoring programs was the major goal

of this study. Overall, most of the methods were relatively useful for sampling their intended

habitat type (see table 2). Samples that collected higher biomass and numbers of invertebrates

tended to take longer to process, but provided a more representative sample. Samples that

involved collecting vegetation took the longest to process due to the high numbers of

invertebrates and difficulty in extracting invertebrates from plant matter. Because some of

these methods used equipment constructed in-house from readily available hardware, there

was a wide range of equipment costs, with higher cost equipment being necessary for the most

widely used (and therefore comparable) sampling techniques. Any sampling that took place in

23

intertidal areas was more limited in spatial and temporal flexibility than samples taken in

channels.

Total biomass and community composition of the samples varied by habitat and sampler type

(see table 3).

24

Table 2. Qualitative evaluation of logistical feasibility of invertebrate sampling methods tested in phase I of our pilot study, with score of 1-3 in bold,

color-coded, with 1 = positive (green), 2= neutral (yellow), and 3= negative (red). Methods with mostly positive scores were chosen for the next phase of

sampling.

Me

tho

d

N

Sam

ple

colle

ctio

n t

ime

Sam

ple

pro

cess

ing

tim

e

Equ

ipm

en

t

cost

s

Pe

rmit

s

Tim

e/L

oca

tio

n

Sen

siti

vity

Ease

of

use

Co

mp

arab

ility

Co

nsi

ste

nt?

Size

of

catc

h

Incl

ud

ed

in

Ph

ase

II?

PVC core 6 1: 20 min.

1: 10 min 1: <$20 1: none

2:Bottom cannot be too hard

1: Very easy to deploy as long as water is less than 1.2m deep

2:4" benthic cores are widely used, though not in the Delta

1: yes 2:medium Yes

Ponar grab

2 1: :20 min.

1: 10 min 3:$1500 1: none

2:Bottom cannot be too hard

2:Heavy, and sometimes does not close properly.

1: Used by IEP long-term monitoring

1: yes 2:medium Yes

Benthic trawl

3 1: 20 min.

3: Picking Algae, 4+ hrs

3: $$$ 3: ESA take listed fish

2:Bottom must be clear of snags

2:Can be difficult to make sure it stays on the bottom.

1: Net size is used by IEP for oblique mysid trawl

1: Yes 2:medium Yes

Sweep nets

12 1: 15 min.

3: Picking vegetation, 4+ hrs

2:$80- $150

1: none

1: No restrictions on timing or location.

1: Easy and fast, but not very consistent

3:Seldom used quantitatively, difficult to standardize

2:Not really 1: Large Yes

Hester-Dendy disk sets

12 2:Two site visits

1: 10 min. 2: $30 each

1: none

3:Must be hidden from view, high marsh may be difficult to access

1: Easy to deploy, may be hard to re-locate.

2:EPA standard method, but not used in the Delta

1: Yes 3:small No

25

Leaf packs

12 1: Two site visits

1: 10 min. 1: <$1 1: none



2:Used in other estuaries, but not here.

1: Yes 2:medium Yes

Mesh scrubber

12 2: Two site visits

1: 10 min. 1: <$5 1: none



2:Used in marine systems, less in marshes

1: Yes 3:tiny No

Throw traps

3 1: 30 min


1: <$40 1: none

3: Difficult to find area flat enough to deploy trap.

3:Hard to transport, hard to "throw", and labor-intensive.

2:Used on the East Coast, less so here.

2:Not really 3:small No

Marklund sampler

6 1: 15 min.


1: <$40 1: none

1: Easiest at low tide

2:Hard to use consistently

3:Not widely used

2:somewhat 1: Large No

Fallout traps

6 2:Two site visits

1: 10 min. 1: <$10 1: none

3:Must be left out for 8-24 hours, on marsh plain that may be inaccessible at certain tides.

2: Need to be sure they do not tip over, need to be able to come back to pick them up.

2:Used previously on BREACH studies, other estuaries

1: Yes 3:small Yes

Neuston net

3 1: 15 min.

3: High variation, 4hrs+

2:$200- $300

3: ESA take listed fish

1: Just need to sample first, before the boat disturbs the water!

1: Can be used with or without a boat.

1: Used in Yolo Bypass, Sacramento river special studies in Delta

1: Yes 2:medium Yes

Table 3. Summary statistics for each sampler type.

Method N Habitat Average Taxon richness

SW index

Catch per sample (SE)

CPUE (SE) Coefficient of Variation for CPUE

Effort units Proportion fish food (SE)

Top four most common taxa in samples (in order of abundance)

PVC core 6 Benthic 4.67 1.06 25.3 (3.04) 3123.7 (374.38) 0.72 Per m2 0.33 (0.04) Hirudinea, Hyllella,

oligocheates, eggs

26

Ponar grab

2 Benthic 11.50 1.23 221 (103.94) 9567.1 (4499.77) 0.94 Per m2 0.04 (0.01) Oligocheates,

Corbicula, Hydracarina, Gastropods

Benthic trawl

3 Benthic 20.00 1.03 1379.3 (560.28) 40.7 (18.02) 1.33 Per m3 0.65 (0.15) Cladocera, Oligocheates, Hydracarina, Gastropods

EAV sweep net

6 Emergent, vegetation

11.67 1.92 50.7 (9.52) 50.7 (9.52) 1.13 Per g dry weight veg

0.55 (0.03) Oligocheates, Corixidae, Hyllella, Cladocera

Hester-Dendy disk sets

12 Emergent Vegetation

5.00 1.07 25.5 (2.64) 25.5 (2.64) 1.24 Per each 0.47 (0.03) Planaria, Oligocheates, Hyllella, Hirudinea

Leaf packs


6.33 1.29 46.8 (3.89) 3.3 (0.29) 1.08 Per g dry weight veg

0.60 (0.02) Hyllella, Planaria, Eggs, Hirudinea

Mesh scrubber


6.45 1.36 42.8 (3.25) 42.8 (3.25) 0.83 Per each 0.44 (0.03) Planaria, Hyllella, Oligocheates, Nemertids

Throw traps

3 Emergent vegetation

17.67 1.78 838.3 (130.4) 1441.7 (270.0) 0.74 Per m3 0.10 (0.04) Oligocheates, Hydracarina, Gastropods, Formicae

FAV sweep net

6 FAV 18.00 1.56 3069.3 (189.3) 1894.8 (658.1) 0.40 Per g dry weight veg

0.43 (0.11) Oligocheates, Hyllella, Planaria, Gastropod

SAV sweep net

6 SAV 19.60 1.97 3082 (268.7) 1966.7 (335.5) 1.22 Per g dry weight veg

0.55 (0.01) Hyllella, Gastropods, Oligocheates, Cladocera

Marklund sampler

6 SAV 21.00 2.24 949.8 (120.71) 445.7 (28.1) 0.40 Per g dry weight veg

0.36 (0.04) Hyllella, Gastropods, Oligocheates, Planaria

Fallout traps

6 terrestrial/ surface

3.00 0.47 28.2 (1.60) 60.7 (3.44) 0.34 Per m

2/hour

0.99 (0.00) Collembolla, Diptera

Neuston net

3 terrestrial/ surface

24.67 2.58 411.7 (108.43) 7.1 (2.06) 0.87 Per m2 0.78 (0.03) Formicea, Aphidae,

Diptera, Oligocheates

27

Table 4. Dominant invertebrates found in the samples and a little about them.

Phylum Class Order Family Genus Common name habitats Functional group fish food?

Annelida Hirudinea Leech

emergent veg,

infauna predator, parasite probably

Annelida Oligocheata Oligocheate

Arthropoda Arachnida Araneae Spider

Arthropoda Arachnida

Hydracarin

a mite vegetation predator, parasite

Arthropoda Branchiopoda Cladocera Cladocera

Arthropoda Crustacea Amphipoda

Crangonycitid

ae Crangonyx Crangonyx

Arthropoda Crustacea Amphipoda Gammaridae Gammarus

aquatic veg, sub

and intertidal

mudflats

scavenger, predator,

omnivore

salmon, smelt,

resident fishes

Arthropoda Crustacea Amphipoda Hyalellidae Hyalella vegetation scraper

salmon, smelt,

resident fishes

Arthropoda Insecta Coleoptera

Hydrophilida

e

water scavenger

beetles

larvae predators,

adults collectors

Arthropoda Insecta Collembola Springtail

Arthropoda Insecta Diptera

Chironomida

e Midge

vegetation,

benthos collector

salmon, smelt,

resident fishes

Arthropoda Insecta Diptera Ephydridae

Shore and brine

flies lentic-littoral

Arthropoda Insecta Diptera fly larvae

Arthropoda Insecta

Ephemerop

tera Baetidae Mayflies lotic 1

collector 1

Arthropoda Insecta

Ephemerop

tera Caenidae

Small

squaregilled

mayflies lotic 1

collector 1

Arthropoda Insecta Hemiptera Aphididae Aphid

28

Arthropoda Insecta Hemiptera

Belostomatid

ae giant water bugs

lotic-

depositional,

lentic-littoral predator (piercer)

Arthropoda Insecta Hemiptera Corixidae water boatmen

lentic-vascular

hydrophytes,

lotic depositional generally herbivores, some predators

Arthropoda Insecta Hemiptera Gerridae Water striders

lentic-limnetic

surface, lotic-

depositional

surface generally predators

Arthropoda Insecta Hemiptera

Hydrometrid

ae water measurers

floating or

emergent

vegetation predators

Arthropoda Insecta Hemiptera Mesoveliidae water treaders

lentic-littoral,

lotic-

depositional predators

Arthropoda Insecta Hemiptera Vellidae

broad

shouldered

water strider

lentic-limnetic

surface, lotic-

surface

Arthropoda Insecta

Hymenopt

era Formicidae Ant

Arthropoda Insecta

Hymenopt

era

Arthropoda Insecta Odonata Aeshnidae darners lentic-littoral1 predator

1 fish

1

Arthropoda Insecta Odonata

Coenagrionid

ae damselfly lentic and lotic1 predator

1 salmon, fish

1

Arthropoda Insecta

Thysanopte

ra Thrip

Arthropoda Insecta Tricoptera Hydroptilidae micro-caddisfly

lotic and lentic-

erosional, lentic-

littoral herbivores, collector

Arthropoda Malacostraca Decapoda Palaemonida Exopalaemon

29

e

Chordata Actinopterygii

Atherinifor

mes

Atherinopsid

ae Menidia

Cnidaria Hydrozoa Hydrida Hydridae Hydra

Mollusca Bivalvia Myoida Corbulidae

Potamocorbul

a

Mollusca Bivalvia Veneroida Corbicula Asian Clam

infauna, bethic

and lotic

benthic feeders

(sturgeon)

Mollusca Gastopoda

Mollusca Gastropoda

Mollusca Gastropoda

Nematoda

Nemertea Enopla

Monostilife

ra

Tetrastemma

tidae Prostoma Ribbon worm

Platyhelminthe

s Turbellaria Tricladida Planaria Girardia flatworm

Arthropoda Copepoda Calanoida

Calanoid

copepod

Arthropoda Copepoda Cyclopodia

Cyclopoid

copepod

Arthropoda Malacostroca Amphipoda Corophiidae Corophium

30

Organisms collected:

A wide range of types of organisms was collected (Figure 10). Most were arthropods and annelids, with

mollusks and planaria being significant parts of some samples (Table 3, 4). There were significant

differences in community composition between sampler types. (Figure 10, PERMANOVA F = 1.931, R2 =

0.264, p = 0.001).

Insects, amphipods, cladocera, copepods, collembolla and larval fish, all of which appear regularly in

Chinook Salmon or Delta Smelt diets, made up over half of the total catch, though this varied by sampler

type (Figure 11).

Some fish were collected incidentally to our invertebrate collections (Figure 12). Sweep nets in

emergent vegetation collected the greatest number of fish, averaging one fish per sample. None of the

fish were listed species; the one unidentified individual cannot have been an osmerid based on the size

(6.5 mm) during the time period it was collected. Delta Smelt and Longfin Smelt would all be expected to

be greater than 20mm by August (Baxter et al. 2015).

31

Figure 10. Mean proportional abundance of different taxa collected by each sampler type. Sampler

types are grouped by target habitat types.

Figure 11. Mean proportion of catch that regularly occurs in salmonid or Delta Smelt diet analyses.

32

Figure 12. Total catch of fish for each sampler type.

Differences between habitat types:

This pilot study was designed to test which samplers work in a variety of habitat types and not to

directly compare invertebrate abundance between habitat types; as a result, we cannot make

inferences as to absolute or relative abundances as they relate to habitat factors. The only sampler type

that was used in more than one habitat type was the sweep net/dip net, and the results of a negative

binomial glm found EAV had significantly lower CPUE and richness than FAV or SAV (table 5). There was

no difference in catch of fish food invertebrates between habitat types (table 5); however, post-hoc

power analyses indicated we did not have sufficient sample size to detect a significant difference

between groups (power = 0.10, effect size = 0.21, p = 0.05). We will increase sample size in phase II of

the study to better differentiate invertebrate abundance between habitat types.

33

Figure 13. Mean catch per gram dry weight of vegetation (number of bugs, +/- 1 sem) collected by

the d-frame sweep net/dip net, by habitat type.

Table 5. Difference in values and significance for the results of negative binomial models comparing

benthic samplers. * - significant at p<0.05, + - close to significant, p <0.1

Sweep Net comparison

SAV

FAV

Diff Pr(>|z|) Diff Pr(>|z|)

CPUE

EAV 1916.063 <0.001* 1844.093 <0.001*

SAV

-71.9 0.998

Species Richness

EAV 7 0.0322* 5 0.162

SAV

-2 0.760

Proportion fish diet invertebrates

EAV -0.036 0.720 -0.009 0.903

SAV

0.028 0.917

34

Differences between samplers within habitat types

Benthic samplers:

Of the three benthic samplers we tested, the PVC core had significantly lower total catch and species

richness than the other samplers (Table 6, Figures 14 and 15). The benthic trawl had higher total catch

and species richness than the PVC core (Table 6, Figures 14 and 15), and it had the lowest coefficient of

variation in both catch per unit effort and species richness (Figure 16). It was also more effective at

catching fish food organisms than the ponar grab, particularly Cladocera. The ponar grab was most

effective for catching benthic infauna, especially Corbicula, though sample size for ponar grabs (n=2)

was too low for statistical comparisons. Both the ponar grab and the benthic trawl were moderately

difficult to use, requiring a boat capable of trawling, ideally with a hydraulic winch, and relatively

expensive equipment (Table 2). The PVC corer, in comparison, was very cheap and easy to use.


benthic samplers. * - significant at p<0.05, + - close to significant, p <0.1

Ponar Grab Benthic Trawl

Diff Pr(>|z|) Diff Pr(>|z|)

Total Count

PVC core 195.6667 0.006* 1354 <0.001*

Ponar Grab 1158.333 0.091+

Species Richness

PVC core 6.833333 0.023* 15.33333 0.023+

Ponar Grab 8.5 <0.001


PVC core -0.28617 0.295 0.325959 0.477

Ponar Grab 0.612128 0.006*

Emergent aquatic vegetation samples:

In emergent vegetation (EAV), we used three different passive substrates (leaf packs, mesh scrubbers,

and Hester-Dendies), and two active methods (sweep nets and throw traps). Due to problems when

collecting the artificial substrates, some invertebrates were dislodged and we could not tell which

substrate they came from, so they were not included in these analyses. The active methods (sweep nets

and throw traps), had a trend towards higher total catch than the passive methods (Figure 15, Table 7),

though only the throw traps had significantly higher catch. Both the throw traps and the sweep nets had

significantly higher species richness (Figure 14, Table 7) however most of the catch from the throw-traps

do not contribute to fish diets (Figure 11). Surprisingly, the coefficients of variation in total catch and

species richness were about the same for active and passive methods (Figure 16). The passive methods

did not differ significantly from each other in total catch. However there was a trend towards leaf packs

35

having a higher proportion of invertebrate types present in fish diets. Hester-Dendies tended to have

the lowest total catch and highest coefficient of variation in catch (Figures, 15, 16).

Half of the substrates were left out for 21 days, and the other half were left out for 42 days, with

significantly higher catch at the 42 day time point (z=2.26, p = 0.023, negative binomial glm).

The throw trap and sweep net only required a single trip into the field, whereas all the passive samplers

required two trips to the field. Once in the field, the throw trap was extremely difficult to use and could

only be deployed on flat, soft ground with sparse vegetation. In comparison, all the other sampling

methods were much easier to deploy (table 2).


sampler types used in emergent vegetation. * - significant at p<0.05, + - close to significant, p <0.1

Hester Dendy Leafpack Mesh Scrubber Throw trap

Diff Pr(>|z|) Diff Pr(>|z|) Diff Pr(>|z|) Diff Pr(>|z|)

Total Count

Sweep Net -25.17 0.57 -3.83 1 -7.85 0.999 787.7 <0.001*

Hester-Dendy 21.33 0.460 17.32 0.704 812.8 <0.001*

Leaf Pack

-4.02 1 791.5 <0.001*

Mesh

Scrubber

795.5 <0.001*

Species richness

Sweep Net -6.667 <0.001* -5.33 <0.001* -5.21 0.989 6 0.29

Hester-Dendy 1.33 0.895 1.45 1 12.67 <0.001*

Leaf Pack

0.121 0.642 11.33 <0.001*

Mesh

Scrubber

11.21 <0.001*


Sweep Net -0.076 0.995 0.056 0.999 -0.109 0.989 -0.450 0.011*

Hester-Dendy 0.131 0.729 -0.033 1 -0.374 0.058+

Leaf Pack

-0.165 0.642 -0.505 <0.001*

Mesh

Scrubber

-0.341 0.069+

Floating aquatic vegetation samples:

The only way we found to sample floating vegetation was to collect a dip-net sample of the vegetation

and manually remove the invertebrates. Since there was only one sampler type, we cannot compare

multiple methods within the FAV habitat, however CPUE and richness on invertebrates collected with

the dip-net in FAV was similar to the same net used in SAV (Figure 13, figure 5). These samples were

36

relatively fast to collect, but sorting the invertebrates in lab from amidst the roots of the vegetation took

significant time (Table 2).

Submerged aquatic vegetation:

The Marklund sampler had significantly lower total catch than the sweep net and a trend towards lower

catch per weight of vegetation (Table 8). They had similar percentage of catch important to fish diets

(Table 3, 7, figures 11, 15). The Marklund Sampler did have a lower variation in catch, but was difficult

to use (figure 16). Both samplers took similar amounts of time (table 2).



Marklund

Diff Pr(>|z|)

Sweep net Total Count 2132.17 0.0046*

CPUE 1521.13 0.079+

Species richness 0.667 1

Proportion food

invertebrates 0.07 0.991

Surface and terrestrial invertebrates:

The neuston trawl had significantly higher total catch (Figure 15, table 3, 9) and species richness than

fallout traps (figure 14, Table 3, 9), and a slightly lower percentage of fish food invertebrates (figure 11,

table 3, 9). The neuston trawl was also much faster than the fallout traps (3 minutes instead of 6+ hours,

table 2).



Neuston trawl

Diff Pr(>|z|)

Fallout trap Total Count 2657.7 <0.001*

Species richness 21.67 <0.01*

Proportion food

invertebrates -0.209 0.0298*

37

Figure 14. Mean species richness by sampler type.

0-500

expanded

below {

A

38

Figure 15. Mean total catch (number of individuals) by sampler type, for A) All sampler types, and B)

expanded view of all sampler types to show differences in samplers with catch of <500 individuals.

Neu

sto

n T

raw

l

Mar

klu

nd

Traw

l

Swee

p n

et

Dip

net

Thro

w t

rap

B

39

Figure 16: Coefficient of variation of CPUE for each sampler type.

Discussion All the methods we tested succeeded in collecting macroinvertebrates from tidal wetlands; however,

some methods were more successful than others in consistently sampling invertebrates that are

important to fish diets. Furthermore, many methods involve new techniques not directly comparable to

existing methods. We will explore new methods further before recommending methods for inclusion in

a standardized monitoring program for tidal wetlands.

Q1: Which methods are feasible for inclusion in a long-term study plan?

The first stage in choosing methods to recommend was evaluating logistical feasibility. After weighing

the pros and cons of each sampling method (table 2), we decided to remove some of the methods from

further consideration.

Hester-Dendy disk sets will not be used because they target the same community in a similar

way as leaf packs, but have a lower catch of fish diet invertebrates, a higher coefficient of

variation in CPUE, and are more expensive.

40

Mesh scrubbers will also not be used because they target the same community in a similar way

as leaf packs, but have lower catch of fish diet invertebrates.

Throw traps will not be repeated because they proved very logistically difficult to deploy, could

not be deployed at all in many areas, and had very low catch of fish diet invertebrates.

Marklund samplers will not be repeated because, while they were designed to sample a

standard volume of submerged vegetation consistently, they were difficult to use in a consistent

manner and provided a very similar sample to the sweep nets used in SAV.

Fallout traps will not be repeated because they collected only a subset of the organisms

collected by the neuston tows, they had very low catch, and they were time-consuming to use.

Some methods warranted further testing to better understand how they vary in different

sampling situations.

Sweep nets were easy to use and effectively sampled invertebrates in multiple habitat types.

However, the differences we saw in CPUE between habitat types may be due either to

differences in invertebrate densities, or to differences in effectiveness of the sampling gear in

different habitats. Therefore, we will test the sweep nets paired with other samplers (leaf packs)

to see if multiple samplers all provide similar results.

Leaf packs were successful in collecting invertebrates in emergent vegetation, so we will test

their use in submerged and floating vegetation, and in channel-edge rip rap.

Neuston nets were successful in open-water sampling, so we will test their use along the edge of

vegetation.

We could not test oblique trawls in open water due to problems with our gear, so we will refine

our gear for testing in Phase II.

Q2: How does the colonization of artificial substrates compare to active methods in collecting a

representative sample of the macroinvertebrate community? What kind of artificial substrate

provides the greatest biomass and diversity of organisms important in fish diets?

In emergent vegetation, all artificial substrates provided a diversity and total catch of invertebrates

similar to sweep net samples. However, total catch of invertebrates on the artificial substrates was

relatively low, even after 42 days in the field. Throw-trap samples were more efficient at capturing

benthic as well as epiphytic organisms, but were very difficult to use and the majority of the catch were

not organisms that regularly appear in fish diet analysis (Figure 10). While there was no significant

difference in total catch between the artificial substrates, the leaf packs produced the highest catch of

invertebrates that appear in fish diets, and were significantly lower in cost than the Hester-Dendy Disk

sets (Figure 10, Table 2). Furthermore, using local vegetation as a substrate instead of plastic or

Masonite may provide a more realistic indication of the community growing on emergent macrophytes.

Leaf packs have the added benefit of allowing studies of decomposition rates, which may be important

in describing production and export of detrital carbon. Leaf packs have been recommended as samplers

for wetland invertebrates elsewhere in California (Scatolini and Zedler 1996). Marsh plants were found

to capture significantly more invertebrates than plastic plants, and leaf packs showed significant

differences between a natural marsh and a restored marsh (Scatolini and Zedler 1996).

41

We expected the artificial substrates to have lower variation than active sampling methods, however,

the coefficient of variation in CPUE was similar for sweep nets, leaf packs and mesh scrubbers, and

higher for Hester-Dendy disk sets (figure 14). This indicates that the standardization provided by

artificial substrates may not be as helpful as we had hypothesized due to the extremely high natural

variability of the system. A sweep net, deployed for a standard period of time, may be a more efficient

way of sampling the epifaunal community, because they require only one trip into the field and the gear

is not subject to loss during a long deployment period. Furthermore, because the sweep net samples

had higher species richness, they may be more representative of the entire invertebrate community.

However, our sample size for the first phase was relatively low (n=6 per habitat type), so we believe it is

worth further comparison of the efficacy of sweep nets and the most promising of the passive samplers

(leaf packs).

Sweep nets and throw traps also had some take of fish; none of the artificial substrates had any catch of

fish (Figure 9.5). While none of the fish were listed, we intentionally targeted a time period where we

did not expect listed fish species to be present. In Phase II we will test whether sweep nets are likely to

incidentally take salmon and smelt, or whether their incidental take of fish are primarily non-native

species.

While retrieving the artificial substrates, many of the larger, more mobile invertebrates were dislodged

from the samplers and it was unclear to which sampler they belonged. In future, all artificial substrates

will be distributed separately to avoid this problem. Including these extra bugs in the analysis of artificial

substrate catch may increase species richness, and help differentiate them from the sweep net samples

in terms of both total catch and community composition.

Other comparative studies of efficiency of invertebrate sampling methods have had mixed results. Some

studies found artificial substrates, such as Hester-Dendies, are preferred over kick-net or sweep-net

samples (Blocksome et al 2005), while others found lower diversity and lower catch from artificial

substrates than active methods (Turner and Trexler 1997). The low catch in all the artificial substrates is

surprising since similar studies in Louisiana (Atilla and Fleeger 2000) and Ohio (Blocksome et al 2005)

found abundances of invertebrates >500 after 12 days (Louisiana) or six weeks (Ohio) in the

environment. The large catch from throw traps was quite different from a similar study in emergent

marshes in the everglades. In that study, throw traps collected a lower abundance than Hester-Dendy

disk sets, and both methods had lower catch than sweep net samples (Turner and Trexler 1997). In

contrast, a study from the Platt River found that a throw trap collected higher invertebrate abundance

and species richness than the sweep net (Meyer et al 2011). The wide differences in efficiency of these

methods between regions is likely due to differences in structure provided by different emergent

vegetation types (Spartina versus Scheonoplectus), differences in water temperature and flow, and

differences in major taxa of invertebrates present. This highlights the importance of piloting survey

methods in the region where monitoring will eventually take place, rather than relying on studies from

other regions.

42

Q3: How do benthic cores compare to benthic trawls in quantitatively sampling epibenthic

amphipods?

Surprisingly, we collected few amphipods in the benthic trawl, but we had extremely high catches of

Cladocera in the benthic trawl, and the highest overall catch of fish food organisms. The highest catch of

amphipods was in the PVC core. However, the PVC core sampled in shallower water than either the

trawl or ponar grab, so some of the variation in catch between samplers may be due to habitat

differences. We will continue to use all three sampler types in a broader variety of habitats to tease

apart these differences. The extremely high abundance of Cladocera in the benthic trawls may be due to

vertical migration frequently seen in Cladocera; they have been found to be epibenthic during the day

and rise in the water column at night (Burks et al. 2002).

Q4: How do neuston tows compare to fallout traps for sampling terrestrial and surface

invertebrates?

Neuston tows collected vastly higher catches than fallout traps, with higher diversity in a shorter

amount of time. All taxa collected by the fallout traps were also collected by the neuston tows, so using

both methods may be unnecessary. While they had a slightly higher coefficient of variation in CPUE, this

may be due to the small sample size from this first phase of pilot work (n=3). Neuston tows can be

deployed in a wider variety of habitats, and can collect both emerging insects and fallout insects.

Furthermore, they are more directly comparable to the use of drift nets in the long-term DWR Yolo

Bypass Study (T. Sommer, pers. comm). Therefore, we will only use neuston tows in the next phase of

sampling. Neuston tows have the potential of collecting fish; however, the short sampling time (3

minutes) could be shortened further if listed fish are captured during the second phase of sampling.

Q5: How do samples from the oblique mysid trawls and ponar grabs used by long-term

monitoring in channel habitat compare to these newer methods?

The invertebrates we collected were also found in both salmon and smelt diet studies. Of the fish diet

invertebrates, there were more amphipods and insects, important for salmonid diets, than copepods,

thought to be most important for smelt diets. However, studies of Delta Smelt diets rely on collections

from large channels with high copepod abundance and low insect/amphipod abundance (Slater and

Baxter 2014). A study of Delta Smelt diets from Liberty Island by Whitley and Bollens (2014) found high

percentages of insects (15% by weight), and amphipods (14% by weight). Furthermore, the CDFW diet

study in 2015 found an unusually high incidence of terrestrial insects in Delta Smelt diets, potentially

indicating a diet change resulting from drought conditions (T. Bippus pers. comm).

Of the invertebrates which we considered “non-fish diet”, they may provide important sources of food

in certain circumstances. For example, annelid worms were considered “non-fish diets;” however, a

recent diet study of salmon in the Pacific Northwest found annelids to make up a large percentage of

the diet when they occurred (David et al 2016). Other organisms, particularly platyhelminthes, may be

too soft-bodied to be detected in diet studies.

The few previous studies of invertebrates in vegetated areas of the Delta collected similar species and

had similar species richness compared to our studies. Howe et al (2014) also found high abundances of

43

Collembolla, Diptera, and other insects in neuston tows, as well as high abundances of annelids and

amphipods in benthic cores. Toft et al (2003) also found very high abundances of amphipods and

oligochaetes associated with floating vegetation, though surprisingly did not report any platyhelminthes

or gastropods.

When comparing our petite ponar, PVC core, and benthic trawl to DWR’s full-size ponar grabs, it seems

that DWR’s ponar collects a higher proportion of clams than any of our samplers (DWR unpublished

data). However, because benthic communities vary greatly in space and time, the high abundance of

clams may be more due to the different location of the DWR samples than inherent differences in the

sampling gear. Furthermore, due to logistical difficulties, we only collected two ponar grab samples

during Phase I. In the second phase of the pilot study, we will take benthic samples in more areas and

increase replication.

It was difficult to make comparisons to invertebrates collected by the Fall Midwater Trawl’s mysid net,

or EMP’s zooplankton study, because they historically only recorded catch of mysids and did not record

catch of amphipods (Hennessy 2009). Our nets collected some of the zooplankton most common in the

Clark-Bumpus net samples collected by IEP (Hennessy and Enderlien 2013, Winder and Jassby 2011), but

because our samplers did not target these smaller organisms, they were not a high proportion of the

catch (Figure 9). None of our samples included mysids. This may be due to long-term declines in mysids

in the estuary (Feyrer et al. 2003), or to our sampling being concentrated in littoral areas rather than

pelagic habitat where mysids were historically abundant. In the next stage of our sampling, we will

increase replication of neuston and benthic trawls, and add oblique trawls to better compare to these

long-term surveys.

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Burks, R., D. Lodge, E. Jeppesen, and T. Lauridsen. 2002. Diel horizontal migration of zooplankton: costs

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juvenile salmon habitat in recovering wetlands of the Salmon River estuary, Oregon, U.S.A. Restoration Ecology 10:514-526.

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Stockton, CA. Hothorn, T., F. Bretz, et al. (2016). Package: multcomp. Simultaneous Inference in General Parametric

Models, CRAN R Foundation for Statistical Computing. Howe, E. R., C. A. Simenstad, J. D. Toft, J. R. Cordell, and S. M. Bollens. 2014. Macroinvertebrate Prey

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Hunt, J. W., B. S. Anderson, et al. (2001). A large-scale categorization of sites in San Francisco Bay, USA, based on the sediment quality triad, toxicity identification evaluations, and gradient studies. Environmental Toxicology and Chemistry 20(6): 1252-1265.

Klemm, D. J., P. A. Lewis, F. Fulk, and J. M. Lazorchak. 1990. Macroinvertebrate Field and Laboratory Methods for Evaluating the BIologic Integrety of Surface Waters.in E. P. Agency, editor., Cincinnatti, OH.

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Maier, G. O. and C. A. Simenstad. 2009. The role of marsh-derived macrodetritus to the food webs of juvenile Chinook salmon in a large altered estuary. Estuaries and Coasts 32:984-998.

Marklund, O. 2000. A new sampler for collecting invertebrates in submerged vegetation. Hydrobiologia 432:229-231.

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Nozuka, B., D. Kaff, P. Lehman, L. W. Mecum, C. Messer, L.J. Hansen, J. Ingram, M. Marshall, J. Pedretti, J. Witzman, B. Hendrickson., and G. Van Klompenburg. 2005. Liberty Island Monitoring Program (First Annual Report):54pp.

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Functions and Datasets for Venables and Ripley's MASS. R Project. CRAN.

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Diego Bay. Wetlands 16:24-37.

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Slater, S. B. and R. D. Baxter. 2014. Diet, prey selection and body condition of age-0 Delta Smelt, Hypomesus transpacificus, in the upper San Francisco Estuary. San Francisco Estuary and Watershed Science 12(3): Article 1.

Sommer, T. R., M. L. Nobriga, W. C. Harrell, W. Batham, and W. J. Kimmerer. 2001. Floodplain rearing of juvenile chinook salmon: Evidence of enhanced growth and survival. Canadian Journal of Fisheries and Aquatic Sciences 58:325-333.

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47

Part II: Fish Dave Contreras, Stacy Sherman, and Rosemary Hartman

48

Introduction Shallow water, soft substrate, narrow channels, and vegetation make sampling in tidal wetlands very

difficult; however, assessing wetland fish assemblages is a worthy challenge. Sampling fish in tidal

wetlands can be difficult because no single technique can effectively sample all fish species/sizes in all

habitats. Multiple factors such as habitat obstructions, gear bias/efficiency, gear/mesh size, practicality,

cost, and Endangered Species Act (ESA) take must be considered when choosing sampling methods.

In this study, we tested several fish gear types and their methods to gauge the feasibility of their use in

wetlands and adjacent channels. The information gathered from this pilot work will be used to inform

our next study (phase 2) that will consist of a rigorous gear comparison.

Larval Fish Sampling Questions:

How feasible is it to work at night?

How will each gear be deployed and retrieved?

How much weight is needed for the larval trawl to successfully complete an oblique tow?

What is the minimum depth to successfully complete a tow?

What is the warp scope to gear depth ratio of the larval trawl?

Juvenile Fish Sampling Questions

What is the minimum sampling depth and deployment space for each gear type?

How is each gear type deployed and retrieved?

How long it will take to complete one sample site for each gear type?

What is the most efficient way to sample a site with each gear type?

Methods Before sampling began, a list of invertebrate and fish sampling methods used in tidal wetlands was

derived from discussions by the Food Web and Fish subteams of the PWT. Each subteam developed a

list of hypotheses and metrics to test those hypotheses. While some methods were widely agreed upon

as useful in target habitats, discussion over other methods was marked by uncertainty or disagreement.

The potential sampling methods discussed by each subteam were evaluated for inclusion in this study

based on usefulness of the generated data, difficulty in set up/retrieval, and feasibility of a method

being used for a long-term monitoring project.

Location and Timing

Sampling occurred in the North Delta near Prospect Island, a site planned for tidal wetland restoration

by the FRP program. The general sampling areas chosen were Lindsey Slough, Cache Slough, Liberty

Island, and Miner Slough (Figure 1). Sampling sites were chosen based on the locations of established

49

sites used by other projects and the need to sample various channel sizes. In addition, sampling

occurred at a time when at-risk fish would not be present in the area and no ESA listed fish were caught

during this study.

Figure 1. Sampling locations in the North Delta. Sampling occurred from July to October. Electrofishing

efforts were conducted by the UC Davis North Delta Arc Study and beach seines were conducted by

US Fish and Wildlife Service Delta Juvenile Monitoring Program.

Larval Fish

Two methods were chosen for sampling larval fish: trawling and light traps. Larval trawls were

conducted using a stainless steel ski-mounted sled weighing 15.9kg with 40cm x 40cm mouth opening &

2m long 500 micron mesh net (Figure 2). A flowmeter was placed in the center of the net mouth to

measure sample volume; a Reef Sensus Ultra Depth Logger or Dive Nav’s Blue Buddy was attached to

the bottom of the mouth frame to measure net depth over time. Light traps were constructed of acrylic

plastic with box dimensions of 27.94cm³ where each side had an opening between 4 to 5mm for larval

fish to enter (Figure x). A 12-lumen xenon light was placed on top of the trap, where the light was

scattered by a spiral plastic tube affixed in the center. The bottom of the trap had a 8.9cm circular

opening where a 32oz collection jar was attached to collect the organisms.

50

Figure 2. Larval fish sled (left) and light trap (right).

Sampling was conducted with light traps in one littoral and one open water habitat in both Lindsey and

Miner sloughs. Initially, light traps were to be placed in littoral vegetation in Lindsey and Miner sloughs,

however Miner Slough lacked large vegetated areas and instead, traps were placed in littoral riprap. The

larval sled was only conducted once in Lindsey Slough due to gear issues (see results for more

information). Larval trawl depths from a forthcoming study taken in channels outside Liberty Island and

Miner Slough were used to assess the depth-to-scope ratio and devise an oblique trawl schedule. At

each site the following environmental data were collected: weather, tide stage/water depth, Microcystis

presence, Beaufort scale, specific conductance, temperature, DO, pH, turbidity, and Secchi depth.

During the September new moon, we sampled each littoral site with 4 light traps, placed 50-100 meters

from one another three to five hours after sunset (Figure 3). Each light trap was anchored by an 3.6kg

mushroom anchor weight and set for one hour in Lindsey Slough, but unfortunately the flashlights ran

out of batteries during the subsequent Miner Slough sampling (they lasted ~30 minutes after

deployment in Miner Slough). While the light traps were deployed, a concurrent ten-minute oblique

larval tow was conducted. After 30-60 minutes, all light traps were retrieved and each trap’s contents

were collected in the cod end and preserved in 10% buffered formalin. All larval fish were identified in

the lab.

At each open water site, 2 pairs of light traps were placed approximately 100 meters from one another

(Figure 3). Each pair of traps was hung vertically in the water column; one light was anchored within 1m

from the bottom and the other 3m below the water surface. Traps were set for one hour in Lindsey

Slough and approximately 30 minutes in Miner Slough. After 30-60 minutes, light traps were retrieved;

each trap’s contents were collected in a cod end and preserved in 10% buffered formalin. A concurrent

single ten-minute oblique larval tow was completed in the open water in Lindsey Slough. After retrieval,

the larval sled net was rinsed from the outside and the sample collected into the cod end. All larval fish

were identified to species in the lab.

51

Figure 3. Larval fish sampling methods in littoral and open water habitats.

Due to the limited number of samples, there was not adequate statistical power to rigorously compare

catch between gear types. However, the information gathered from this study helped identify gear

limitations and time constraints for the second phase of this study.

Juvenile/Adult Fish

Several methods were chosen to sample juvenile/adult fish in various habitat types (Table 1). Our efforts

were coordinated with on-going sampling efforts of the UC Davis North Delta Arc study (ARC) and the US

Fish and Wildlife Service Liberty Island study (LI) to reduce redundant sampling and ESA take. Sampling

occurred over two days for each habitat type from August through October, except for open water

habitat where the gears were sampled concurrently. We sampled in similar non-vegetated sampling

sites as the LI beach seine survey on the day before the USFWS sampled. We sampled with fyke and gill

nets within a week of ARC’s electrofishing efforts. At each site the following environmental data were

collected: weather, tide stage/water depth, Microcystis presence, Beaufort scale, specific conductance,

temperature, DO, pH, turbidity, and Secchi depth. All fish caught were identified and measured to the

nearest mm fork length, unless caught by electrofishing or otter trawling, where the fish were measured

to the nearest mm standard length.

52

Electro fishing was conducted by the ARC survey using a Smith-Root electrofishing vessel with a 7.5 GPP

electrofisher. Sites in the Lindsey Slough and Calhoun Cut area were randomly chosen based on the

bank type. Crewmembers stood on the bow of the vessel operating an on/off foot switch, and each

sampling bank type was electrofished for approximately 150 seconds, until the end of the bank type was

reached, or the live well was full. The crew used eight to ten second bursts of electricity along sections

of one shoreline. All fish were collected with a 5mm mesh dip net, placed in a live well and measured.

Table 1. Gear types tested by month and habitat type. Gears that sample the same habitat type were

compared with each other, but not with gears used in other habitat types.

Gear Types Habitat Type General Area Sampled

Electrofishing, Vegetated Littoral Lindsey Slough

Gill Net

Electrofishing,

Small Channel Calhoun Cut Restored Fyke Net,

Cast Net

Beach Seine, Non-vegetated

Littoral Liberty Island Lampara Net,

Cast Net

Otter Trawl, Open

Water/Channels Cache Slough Kodiak Trawl,

Lampara Net

Three gill nets were set in the Lindsey Slough area using a net that measures ~ 30m long x 2.1m high and

composed of 5 different mesh panels that increase by 1.27cm, where the smallest mesh is 2.54cm. The

net was set perpendicular to the shore and due to the length of littoral shoreline, two mesh sizes

(6.35mm, 7.62mm) were fished. The other meshes were wrapped around a U-post and staked to the

shore. The mesh was deployed slowly and once the end was reached, the lead line was attached to an

3.6kg mushroom anchor and sampled between 45-60 minutes. The net was retrieved onto the vessel,

and all fish were removed from the net, placed in a large bin with aerated water, identified, and

measured.

The fyke net mouth measured 0.98m long x 1.17m high with 7.25m long x 1.27m high with wings

composed of 0.02m heavy duty delta stretch mesh. The fyke was composed of seven 0.92m diameter

rings spaced approximately 0.39m apart. The end of each fyke wing was attached by heavy duty zip ties

to a T-post driven into each bank of the Lindsey Slough Restoration Site breach. As the vessel backed

away from the attached wings, hoops of the fyke net were deployed from the vessel. The cod end was

deployed with an attached 3.6kg mushroom anchor and float line. The net was set approximately 10

meters upstream of the mouth of the newly created Lindsey Slough channel at Calhoun Cut at high slack

tide and allowed to fish for the duration of the ebb tide. On retrieval, the cod end was lifted off the

53

ground and placed into the vessel. Each wing was detached from a t-post and brought on board. Any fish

caught were placed into a large bin with water, identified and measured.

Beach seining in Liberty Island was conducted by the USFWS using a net that measures 15m long x 1.2m

high with 3mm delta square mesh. One crew member walked out into the water (up to 1.2m in depth)

holding one end of the net to measure the width and depth of the seine site. The second crew member

then walked to the first crew member and placed their seine pole where depth was recorded. The first

crew member walked parallel to the length of the shore and noted the seine length and site depth. Both

crew members hauled the beach seine up on the shore, leaving the cod end bag in water. The crew then

filled a tub with water, placed the cod end bag in the tub along with any fish caught in the “wings” of the

seine, then identified and measured the fish.

A lampara net was borrowed from the UC Davis fish culture facility, measuring ~70m long and consisting

of the following mesh sizes: 4.7mm at bag, 20mm at mid wing, and 76mm at end wings. We planned to

sample in Liberty Island the day before the USFWS beach seine survey; however, the tides were

unfavorable and only allowed one opportunity to sample the same site with both gear types. During the

first deployment, the net was deployed similarly to the method outlined by the USFWS beach seine. One

crew member walked out into the water (up to 1.2m in depth) holding one end of the lampara net. A

second member then walked to the first crew member. As the first crew member walked along the

shoreline, the second person fed the net out to ensure the net didn’t cut across the seine site. Once the

end of the lampara net was at the shore the second crew member walked back to the shore to hold the

end and the first crew member then walked to the shore. Both crew members hauled the lampara seine

up on the shore, leaving the cod end bag in the water. The crew then filled a tub with water, placed the

cod end bag in the tub along with any fish caught in the “wings” of the seine, then identified and

measured the fish. For the second deployment of the lampara net, the beach was not accessible, so a

different sampling technique was used. The first crew member was dropped in water <1.2m in depth

and given one end of the lampara net (Figure 4A). The net was deployed by a second crew member on

board, as the vessel backed away and encircled the site (Figure 4B). Once the end of the net was

reached, the second crew member was dropped in water < 1.2m in depth and the first crew member

walked over to the second crew member (Figure 4C). Both crew members got back onboard the vessel,

hauled the net onboard the vessel, and placed the cod end bag in a tub filled with water where fish were

identified and measured.

The Kodiak trawl net measured 17m in length and had a 4.9m long x 1.8m high mouth opening that

samples the water’s surface. The bridles were 2.7m, where each bridle was attached to a 15.2m tow

line. The net mouth was approximately 18% smaller than the one used by CDFW’s Spring Kodiak Trawl

survey. The net consisted of 4 panels that graduate down from 41mm to 6mm str. mesh (41mm, 25mm,

13mm, and 6mm). At each site, the cod end from one vessel (referred to as the net boat) was handed

over to a second boat (referred to as the chase boat). The chase boat slowly backed up until the net

boat signaled them to stop and released the cod end into the water. Five pounds of weights were added

to each bottom corner of the net mouth on the net boat and deployed simultaneously off the starboard

of the vessel. A Reef Sensus Ultra Depth Logger was attached to the port side bottom corner of the

54

mouth. The net boat oriented itself in the towing direction and slowly released the towing line into the

water. The chase boat came along the starboard side of the vessel and was passed one of the bridles,

where it was clipped to a towing location. The vessels came apart from each other (approximately 9.1m)

and conducted a 5 minute tow with the float line along the top of the water. After the tow was

completed, the vessels came together and the net was retrieved along the starboard side. Contents

from the cod end were emptied into a tub with water and fish were identified and measured.

Figure 4. Pictures depicting how the lampara net was set near an inaccessible beach.

A newly constructed lampara net was used during trials, comparing it to the otter and Kodiak trawls. The

net was constructed to be lighter than the previous lampara net used to reduce crew fatigue, retrieve

the net faster, and make it easier to use in small channels. The lampara net measured 65m long and

sampled a maximum depth of approximately 3m and samples the water’s surface. The cod end

consisted of 4.8mm sq. mesh with floor material consisting of three mesh panels (4.8mm, 12.7mm, and

76.2mm). The wings consisted of three mesh panels: 76.2mm, 88.9mm, and 152.4mm. The net was set

similarly as a purse seine (Figure 5). One end of the lampara was attached to a sea anchor and buoy and

thrown overboard with the current (Figure 5A). One crew member was in charge of deploying the float

line and the other was in charge of deploying the lead line. As the boat slowly backed up against the

current, both crew members deployed the gear in a straight line. Once the net was almost fully

deployed, the end on the boat was held on the vessel cleat. The vessel looped back around to the

“anchor” end of the lampara net and attached it another cleat (Figure 5B). The vessel backed up again

for approximately 30 seconds to push fish into the back of the net (Figure 5C). It was then retrieved onto

the vessel where the cod end was placed in a tub of water and fish were identified and measured.

A C B

55

Figure 5. Pictures depicting how the lampara net is set in open water and channel habitat.

Otter trawls were conducted by the ARC study using a net with a 4.3m long x 1.5m high mouth opening

and a total length of 4.9m, composed of 35mm stretch nylon mesh in the body and 6mm stretch mesh

nylon in the cod end bag. The otter trawl doors were composed of 1.9cm thick plywood and measured

76.2 x 38.1cm. The gear was deployed onboard a vessel where the cod end was tossed off the stern of

the boat. Once the net was completely deployed, two crew members each held onto an otter trawl

board. The two crew members signaled one another and deployed the otter trawl doors simultaneously

off the stern of the vessel, where it dragged along the bottom. After five minutes, the otter trawl boards

and net were retrieved back onboard the vessel. The cod end was emptied into a tub with water and

fish were identified and measured. Otter trawls were conducted in Cache Slough alongside the Kodiak

trawl and the lampara net for three tows. Each gear was positioned along the west bank, center

channel, or east bank and each gear rotated one lane to the “east” for the remaining tows.

The cast nets had a 1.8m diameter mouth opening with 4.7mm mesh size and weighted 0.7kg per radius

foot. We originally planned to use cast nets during many of our sampling days, but were dropped in

many instances due to time constraints. Cast nets were used in North Liberty Island during our lampara

net seine sampling and Calhoun Cut upstream of the fyke net sampling. The net was deployed by one

crew member for each site. The net was tossed, allowed to sink, and then retrieved. During each toss, a

mouth opening percentage was visually estimated and recorded. All fish caught were placed in a tub

with water, identified and measured.

B A

Current

C

56

Results

Larval fish methods

Larval fish sampling at night was found to be feasible despite some problems. Light traps were

successfully set and retrieved in Lindsey Slough in littoral and open water sampling, but some issues

arose during the process. All light trap samples at the bottom in open water were retrieved upside down

due to the way they were attached to the top trap and float line. All light trap samples in Miner Slough

were cut to approximately 30 minutes because of battery issues. Another issue arose in Miner Slough,

where a pair of light traps in open water was not immediately recovered during the night. The last issue

for night sampling was the larval trawling near the littoral vegetated areas. The gear was towed

alongside the vegetation, but the wind pushed the boat and fishing gear into the vegetation causing it to

be inundated with weeds. The gear was retrieved and put back into the water alongside the boat to

clean all the vegetation out of the net. Unfortunately, the net was long enough that the cod end was

shredded by the boat propeller, so only one larval tow was completed that night.

The weight of the larval trawl sled appears to be a little too heavy to conduct an oblique tow based on

the depth logger data recorded for the propeller (prop) boat (Figure 6). Although not a focus from this

study, a jet motor was also used to tow the larval sled and will be discussed later. Depth logger shut off

for oblique tows during that last 2 minutes, so the last two minutes of the tow are comprised of the last

4 repeated measures made by the device since the sled was at the water’s surface. Since only one

oblique tow was successfully completed during this pilot study, additional tows were made on a later

date to construct a tow schedule (Table 2). The warp scope to gear depth is approximately 2 to 1 (ex. for

gear to tow at 8 ft, 16 ft of cable will need to be let out from the vessel).

57

Figure 6. Larval sled trawl tow depth.

Table 2. Larval sled tow schedule.

Site Depth

Cable Length Clock Time for 10' Pulls

(feet) (feet) (cable remaining at end of pull)

≤ 5 10 0:00

(0)

6-10 20 5:00 0:00

(10) (0)

11-15 30 6:40 3:20 0:00

(20) (10) (0)

16-20 40 7:30 5:00 2:30 0:00

(30) (20) (10) (0)

21-25 50 8:00 6:00 4:00 2:00 0:00

(40) (30) (20) (10) (0)

26-30 60 8:10 6:40 5:00 3:30 1:40 0:00

(50) (40) (30) (20) (10) (0)

31-35 70 8:34 7:08 5:42 4:16 2:50 1:24 0:00

(60) (50) (40) (30) (20) (10) (0)

≥ 36 80 8:45 7:30 6:15 5:00 3:45 2:30 1:15 0:00

(70) (60) (50) (40) (30) (20) (10) (0)

Larval fish were caught with both gear types, but the majority was caught in the light traps in Lindsey

Slough in the littoral vegetated area (Table 3). Both gear types caught Threadfin Shad only in the open

water habitat , and at least one Mississippi Silverside was caught in each habitat sampled with light traps

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

5.5

6

00:00 01:00 02:00 03:00 04:00 05:00 06:00 07:00 08:00 09:00 10:00

De

pth

(m

) Time (mm:ss)

Propellar Boat Tow (Floor Depth 5.8m)

58

(Table 3). In addition to the fish caught, many of the samples from the light traps in Lindsey Slough in

the littoral vegetated area contained high numbers of zooplankton and other invertebrates. These data

were not quantified; however the samples were kept for future reference.

Table 3. Light trap and sled fish catch, fork lengths, and standard deviation (SD) in various habitats

(shaded = Larval sled gear type).

Light Traps Light Traps Larval Sled Light Traps

Lindsey Slough Lindsey Slough Lindsey Slough Miner Slough

Littoral Vegetation

(n=4)

Open Water Open Water Littoral Riprap

(n=4) (n=1) (n=4)

Fish Species Total

Catch

Mean

FL

(mm)

SD Total

Catch

Mean

FL

(mm)

SD Total

Catch

Mean FL

(mm) SD

Total

Catch

Mean

FL

(mm)

SD

Mississippi Silverside 17 8.8 2.5 5 15.8 2.3 - - - 1 14 0

Threadfin Shad - - - 1 15 0 1 11 0 - - -

Juvenile and adult fish

For the juvenile/adult sampling methods, the beach seine and otter trawl were not evaluated because

they were sampled by other agencies. The electrofishing method was evaluated because our crew

sampled one day in August in place of the ARC study.

We successfully completed one gill net set, while the other two were obstructed by dense vegetation.

The gear was set in depths ranging from 0.2-2.9m, and out a maximum 30m from the shore. The net

sampling time ranged from 47-60 minutes. Only one net sampled fish and unfortunately one contained a

drowned cormorant (Table 4).

Electrofishing in Lindsey/Barker Slough and Calhoun Cut occurred in a channel ~6.5m across and ~1.8m

deep. The wind pushed the boat into the shoreline; sampling proved to be difficult and sections of

habitat needed to be sampled in other locations. Sampling took approximately 150 seconds and caught

an assortment of fish (Table 4 and 5).

59

Table 4. Electrofishing and gill net fish catch in littoral habitat.

Barker Sough Lindsey Slough Calhoun Cut

Fish Species E-fish Gill Net E-fish Gill Net E-fish Gill Net

Black Crappie 1 - 1

No Catch

(gear fouled)

-

No Catch

(gear fouled)

Bluegill Sunfish - 1 2 -

Brown Bullhead 1 - - -

Golden Shiner 6 - - -

Largemouth

bass 7 1 8 7

Prickly Sculpin - - 1 -

Redear Sunfish 3 2 2 2

Sacramento

Sucker 2 - 1 -

Shimofuri Goby - - - 1

The fyke net (n=1) had some issues when sampling in the breach of the Lindsey Slough Restoration

breach due to the water velocity and depth of the channel. During two instances, the fyke net wings did

not hold when staked in with u-posts, so the net was moved upstream and t-posts were placed higher

on the bank. In addition, the fyke net did not block the entire channel as the recorded channel depth

was 2.1m, which is 0.93m higher than the fyke net. In addition, since the t-posts were set higher on the

bank, this allowed wing gaps between the channel floor and lead line. Due to these issues, no fish were

caught (Table 5) during the duration of the ebb tide (~5 hours).

Table 5. Electrofishing and fyke net fish catch, mean standard length, and length standard deviation in

small channel habitat. Please note that (*) denotes a subset of fish were measured.

E-Fishing Fyke Net

Fish Species Total Catch Mean SL (mm) SD

Largemouth Bass* 8 223 31

No

Catch

Mississippi Silverside 1 70 0

Sac. Pikeminnow 1 360 0

Sac. Sucker 1 380 0

Striped Bass* 20 244 50

60

The lampara net worked fairly well for non-vegetated littoral (n=2) and open water (n=3) applications.

Deployment time is a little longer than the beach seine, taking approximately 10 minutes, as opposed to

5 minutes. The gear can be used in in depths as low as 0.9m and needs ~ 250m² of seine space for

successful deployment. In the open water of Cache Slough, filamentous algae catch ranged from one

liter to several gallons and made finding fish difficult. We suspect some small fish may have been tossed

over with the algae as fork lengths as low as 19mm were recorded at this site. Although the number of

replicates was low, the number of species and fish caught appear to be promising for this gear type

(Table 6).

Table 6. Beach seine and lampara net fish catch and fork length ranges in vegetated littoral habitat.

Blank spaces indicate no catch/FL Range.

Fish Species

Lampara Net Beach Seine

LI001W

Total

Catch

LI005W

Total

Catch

Mean FL

(mm) SD

LI001E

Total

Catch

LI004E

Total

Catch

LI005W

Total

Catch

Mean FL

(mm) SD

Black Bass 4 - 45 26 - - - - -

Common Carp 3 - 71 21 - - - - -

Golden Shiner - - - - - - 3 48 5

Largemouth Bass 15 1 79 22 - - 1 55 0

Mississippi Silverside 76 5 48 17 146 12 23 39 11

Prickly Sculpin 1 - 70 0 - - - - -

Redear Sunfish 3 - 105 54 - - - - -

Shimofuri Goby 5 1 38 11 3 - 9 43 11

Striped Bass 8 - 89 20 - 4 - 85 14

Tule Perch 1 - 98 0 - - - - -

Yellowfin Goby - 1 76 0 - - - - -

61

The Kodiak trawl (n=3) had one issue that likely influenced the catch. The 2.3kg weights attached to the

bottom corners of the mouth did not allow the mouth to fully open as shown by the depth logger data

(Figure 7). Since the net mouth was closed during most of the tow, no fish were caught during the first

two tows, but on the third tow caught the most fish for all gear types (Table 7). Total gear sampling time

was approximately 10 minutes (based on a 5-minute tow time) and the gear can be deployed in depths >

2m with a minimum of approximately 35m of channel width sampling space.

Figure 7. Kodiak trawl port side net mouth opening depth. Shading provides an approximation for the

tow duration and presented as a visual aid to show the lack of net mouth depth achieved.

62

Table 7. Lampara net, Kodiak trawl, and otter trawl fish catch in Cache Slough open water habitat.

Column position represents the towing lane for each gear type from West to East.

Fish Species Trawl 1 Trawl 2 Trawl 3

Lampara Kodiak Otter Otter Lampara Kodiak Kodiak Otter Lampara

American Shad 1 - - - - - - - -

Bluegill 1 - - - - - - - -

Largemouth Bass 2 - - - - - - - -

Misc. Sunfish - - 3 1 - - - 1 -

Mississippi

Silverside 5 - - - 22 - 43 - 2

Prickly Sculpin - - - 1 - - - - -

Shimofuri Goby 2 - 1 3 - - - 2 -

Striped Bass - - - 1 - - - 4 -

Threadfin Shad - - - - - - - - 2

Cast nets were deployed in North Liberty Island (n=18) and upstream of Calhoun Cut (n=5) in depths <

3m on the same sampling days as the lampara net seine and fyke net, respectively. Each deployment

and retrieval took ~ 5 minutes and percent mouth opening varied among crew members and each

deployment (Figure 8). Fish were only caught in two casts during the two sampling events.

63

Figure 8. Cast net mouth opening variation for each crew member and each deployment.

Discussion Both larval fish gear types were deployed and retrieved as outlined in our SOPs without much difficulty

except in an instance where a pair of light traps in the middle of the channel was not immediately

recovered. This may have occurred because of the way the light traps were attached to one another

(Figure 3) and the strong tide. It could be that the strong tide pushed the light traps well below the

surface or the sample became inundated with vegetation, but we do not know for certain why this

occurred. The light traps were retrieved 36 hours later, approximately 940m downstream from where

they were set, with no damage.

Although larval light traps and oblique trawls can be sampled at night, the limited visibility requires extra

caution when sampling. Understanding your vessel’s tracking line while under tow will determine how

close to vegetation you can deploy the gear to deter a net full of aquatic vegetation. During our gear

methodology trials, wind strength was a factor by pushing the vessel into the vegetation and causing a

non-valid tow. Caution must be used to ensure the towing sled and the light traps do not entangle one

another when being sampled simultaneously.

We sampled the larval sled with both a jet and prop motor and found the prop motor to be better

equipped for towing. In our instance, the jet motor lacked the power of a prop motor and required

continuous speed adjusting to keep the boat tracking in a straight line. Continuous speed adjusting is not

ideal for oblique trawling because the gear will rise and sink causing unequal portions of the water

column to be sampled. The prop boat towed the gear with minimal speed adjustment and the gear

sampled the water column fairly well. Although we describe how different engine types affect oblique

64

trawling, other boat properties such as the length, height, weight, and hull design should be considered

when selecting a vessel for towing.

The feasibility of a long term monitoring program routinely conducting light trap sampling at night may

be limited due to visibility issues and crew fatigue. However, they may be useful to detect the presence

of spawning fish in shallow and vegetated areas where larval tows are not feasible. Although light trap

data is qualitative, they may be useful to detect presence/absence of larval fish and differences in

microhabitat use. Larval trawls produce quantitative data and sample the target species Delta Smelt and

Longfin Smelt as evidenced by IEP larval trawl surveys throughout the Delta.

Gill nets set perpendicular along the vegetated littoral zone proved to be difficult as the lead line did not

sink on two of the three sets. Although gill nets did not work well during this trial phase, the gear will be

included in Phase II of our gear comparisons. The following modifications will be made. To ensure the

net can be used near vegetated locations, gill nets will be set parallel along the vegetation. In addition,

all gill nets will be closely monitored so no birds or mammals are accidently ensnared.

Fyke nets were difficult to set and we encountered some unforeseen logistical issues. The fyke net wings

were blown out of the attached t-posts due to the high water velocity. High velocities coming out of the

Lindsey Slough Restoration breach were not only driven by the main stem of the channel, but also a

western side tributary. Once the fyke net was set up further upstream and past this tributary, the net

stayed in place. Channel depth also posed a problem, as the fyke net did not sample the entire water

column and the lead line was light enough to allow gaps for fish to escape. For phase II of the gear

comparison, weight will need to be added to the lead line and at least an extra 1m of netting will need

to be added on top to effectively capture fish.

Electrofishing went well and no gear or sampling adjustments need to be made. Sampling around

vegetation and in small and shallow channels captured a diversity of fish species and sizes. Surprisingly,

the boat electrofisher was able to sample in a smaller channel in the newly developed Lindsey Slough

restoration site. Thus far, it appears electrofishing catches more fish species and sizes than fyke and gill

nets as seen in a study by Goffaux et al (2005), but a formal gear comparison will need to be made in

phase II.

Of all the gears tested, the lampara net appears to be one of the most flexible and able to sample

unvegetated littoral and pelagic open water habitat. The gear can be deployed in shallow habitat from a

beach using two crew members or deployed from a boat in an inundated site. However, this may pose

difficulty in data comparability because of factors such as the tidal height, the hauling technique, and

the amount of site disturbance may affect the catch. For our next study, we plan to deploy the lampara

net from the boat, as it appears to catch a wide diversity of fish. In addition, all the fish caught by the

lampara net appeared to be in good condition compared to those caught by the Kodiak trawl. UC Davis

uses a lampara net to capture their Delta Smelt brood stock every year and have survival rates ranging

from 62-100% after 72 hours of capture (UC Davis Fish Conservation and Culture Lab staff personal

65

communication). Survival rates will change depending on water temperature and amount of

vegetation/mud/debris caught. This gear will be compared to the beach seine and Kodiak trawl in phase

II.

The Kodiak trawl was able to sample in open water channel habitat, but will require adjustments to

ensure the net mouth stays open. During our first Kodiak trawl trial run, when we attached 6.8kg

weights to each side of the net, it sank under the water and towed the gear along the bottom like an

otter trawl. Five- pound weights were used in this trial and were found not sufficient to keep the net

mouth open. To ensure the net mouth is open in the future, metal spreader bars will be hooked to the

net mouth. The spreader bars will limit the minimum sampling depth to ensure they do not dig into mud

and cause the net to get snagged or filled with mud. Towing this gear in wetlands can be problematic,

which may restrict sampling in the adjacent channel(s) of the wetland. Although the gear is not as

flexible as the lampara net, this gear type is considered to be very effective in capturing juvenile

salmonids and adult Delta Smelt, which may be attributed to the herding effect of the Kodiak trawl,

sending fish into the center of the net (Noel 1980).

The cast net did not show much promise during these initial methodology trials as fish catch was low

and mouth opening was variable among crew members. However, the replicate number was low for this

gear and it is expected that deployment will become more consistent as the crew gain experience. The

main issue with the cast nets is that they are a bit heavy and long which makes it difficult to toss for the

average user. Each toss seldom went five feet from the crew member due to the weight of the net. Even

though this gear type was not effective in the few instances it was deployed, it will still be included in

the phase II gear comparison, as studies have shown fish catch composition and sizes to be comparable

to other gear types including beach seines (Stein et al 2014; Stevens 2006). Hieb and Greiner

(unpublished report) tested various sampling gears in wetlands throughout the upper San Francisco

Estuary and found cast nets to catch a high number of fish species. Since fish catch was low and the gear

was difficult to throw, we plan to use smaller/lighter cast nets with larger mesh size and an attached

throwing ring to increase the mouth opening. Fitec’s EZ Throw 1000 series cast net may assist

everyone’s throwing capabilities allowing a mouth opening of 70% or higher.

Although fish catch and lengths were not a focus of this study, the data were reported here for

qualitative comparisons. Some gears became “front runners” in the number of fish and fish species

caught, but the number of replicates is too low to make a definitive choice on specific gear types in

various habitats. Another observation made was that larval fish appear to be larger in the open water

than in vegetated littoral habitat.

Overall, phase I of this study was an eye opening experience into how to deploy and retrieve gears. We

would recommend that any new monitoring program unfamiliar with various gear types do the

following: 1) go out with another monitoring group that utilizes one of your selected gear types, 2) try

the gear methodology yourself to understand if any modifications need to be made, and 3) incorporate

the modifications and test the gear again. We found that most gears required some sort of modification

66

from when we first deployed it, as descriptions on paper do not always translate to the field. All gear

types were successfully deployed and will be included in the phase II study, except for the light traps due

to issues with potential ESA take. The phase II study will be a more rigorous gear evaluation, where the

results will determine the sampling gears recommended for long-term monitoring in tidal wetland

systems in the Delta and Suisun Marsh. We expect to recommend multiple gear types for sampling fish

based on the habitat, accessibility, target fish species, and cost of each gear type.

References CDFG. 2009. Longfin Smelt incidental take permit for Department of Water Resources California State

Water Project Delta facilities and operations. California Department of Fish and Game Bay Delta

Region. 20pp.

Goffaux, D., G. Grenouillet, P. Kestemont. 2005. Electrofishing versus gillnet sampling for the assessment of fish assemblages in large rivers. Arch. Hydrobiol. 162(1): 73-90.

Hieb, K and T. Greiner. Unpublished report. Tidal Marsh Study Report. California Department of Fish and

Wildlife, Stockton, CA. NMFS. 2009. Biological Opinion and Conference Opinion on the long-term operations of the Central

Valley Project and State Water Project. National Marine Fisheries Service, Southwest Region.

844pp.

Noel, H.S. 1980. Pair trawling with small boats. New York: Food and Agriculture Organization of the

Unites Nations. 77 p.

Stein, W., P.W. Smith, and G. Smith. 2014. The Cast Net: an Overlooked Sampling Gear. Marine and

Coastal Fisheries: Dynamics, Management, and Ecosystem Science 6: 12-19.

Stevens, P.W. 2006. Sampling Fish Communities in Saltmarsh Impoundments in the Northern Indian River Lagoon, Florida: Cast Net and Culvert Trap Gear Testing. Biological Sciences 69:135-147.

UC Davis. November 9, 2015. Email about Delta Smelt survival in the lampara net. USFWS. 2008. Biological Opinion and Conference Opinion on the long-term operations of the Central

Valley Project and State Water Project. United State Fish and Wildlife Service California and

Nevada Region. 410pp.

67

Acknowledgements The Monitoring Team would like to thank the larger Fish Restoration Program for their input and

support of this project. Financial support was provided by DWR. We would also like to thank the IEP

Tidal Wetland Project Work Team and Science Management Team for their assistance in building a

strong study plan. In addition, we thank the US Fish and Wildlife Delta Juvenile Monitoring Program for

coordinating Liberty Island sampling and letting us borrow their fyke and gill nets. A big thanks goes to

the UC Davis North Delta Arc Program crew for allowing us to tow alongside them. Lastly, we thank our

boat operators – Curtis Hagen, Jared Mauldin and Matt Siepert for all the hard work they put into this

study. This work was program element number 311 under the 2015 IEP Work Plan.

FISH RESTORATION PROGRAM PILOT STUDY PHASE I: RESULTS … · the primary goal was to determine which methods were feasible for use in shallow water. A more statistically rigorous

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