Juvenile Salmon Usage of Nearshore Habitats along City of ...Gastric lavage of juvenile chinook shows less terrestrial/riparian input (insects) at sites with retaining structures at
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Juvenile Salmon Usage of Nearshore Habitats along
City of Seattle Marine Shorelines
Wetland Ecosystem TeamSchool of Aquatic and Fishery Sciences
University of WashingtonSeattle, WA
Jason Toft
Charles SimenstadJeff Cordell
Lia Stamatiou
Funded by the Seattle Public Utilities Department
Main Objective:Quantify the abundance and behavior of juvenile salmonids and other fishes directly along marine shoreline habitat types.
Sampling Methods: High tides 5/12 - 8/1/03Spring Tides: Enclosure nets and snorkeling - sand, cobble, riprapNeap Tides: Snorkeling - all sites
Enclosure Nets (n=48):- Samples entire water column- Minimal problems with
obstacles on substrate- Holds fish for 2.75 hours, good
for fish diet analysis- Mesh size not good for small
forage and larval fish- Time and labor intensiveSnorkeling (n=442):- Fish not captured- Dependent on water clarity - Onsite specific behavior and
location patterns- Good at small forage/larval
fish and rare fish- Not so good at juvenile flatfish- Ease of replication
Pros and Cons
All Results are PRELIMINARY!:First detail fish densities from above 3 habitat types (modifications just to intertidal), then include the 2 below (modifications extend into subtidal).
Fish Densities:Between cobble beaches, sand beaches, and rip-rap that ends at the high intertidal, we see minimal differences -all in bottom fishes.
Enclosure Nets: Flatfish (juv. English Sole) at Sand Beaches
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
CobbleBeach
SandBeach
Rip-Rap
Fish
Den
sity
(#/m
3 )
Juvenile Salmon
Forage Fish
Other NearshoreFishesSurfperches
Flatfish
Other DemersalFishesGunnels
Crabs
*
Fish Densities:Between cobble beaches, sand beaches, and rip-rap that ends at the high intertidal, we see minimal differences -all in bottom fishes.
Snorkeling: Crabs at Cobble Beaches, Sculpins at Rip-Rap
0.000
0.001
0.002
0.003
0.004
0.005
CobbleBeach
SandBeach
Rip-Rap
Fish
# /
(Sec
chi d
epth
(m)*
Tran
sect
leng
th(m
)) Other NearshoreFishes
Flatfish
Other DemersalFishes
Gunnels
Crabs
Unknown Fish
* * *
Less Abundant FishAbundant Fish
0.0
0.1
0.1
0.2
0.2
0.3
0.3
0.4
CobbleBeach
SandBeach
Rip-Rap
Fish
# /
(Sec
chi d
epth
(m)*
Tran
sect
leng
th(m
))
JuvenileSalmonForageFishSurfPerchesOtherFish
Fish Densities:When shoreline modifications extend into the subtidal, we see more differences - in pelagic fishes.
Snorkeling: Overall at Overwater and Deep Rip-Rap, Juvenile Salmonids at Overwater, Surfperches at
Deep Rip-RapAbundant Fish
0.0
0.2
0.4
0.6
0.8
CobbleBeach
SandBeach
Rip-Rap Deep Rip-Rap
OverwaterStructure
Fish
# /
(Sec
chi d
epth
(m)*
Tran
sect
leng
th(m
))
JuvenileSalmon
Forage Fish
SurfPerches
Other Fish
* *
*
*
Fish Densities:When shoreline modifications extend into the subtidal, we see more differences - in pelagic fishes.
Snorkeling: Other Nearshore Fishes and Gunnels at Deep Rip-Rap
Less Abundant Fish
0.000
0.005
0.010
0.015
0.020
CobbleBeach
SandBeach
Rip-Rap Deep Rip-Rap
OverwaterStructure
Fish
# /
(Sec
chi d
epth
(m)*
Tran
sect
leng
th(m
))
Other NearshoreFishes
Flatfish
Other DemersalFishes
Gunnels
Crabs
Unknown Fish
*
** * *
Snorkeling: Juvenile Salmonid species groupings at Overwater and Deep Rip-Rap, also greater school sizes at Overwater (numbers above bars)
Salmon Densities and School Sizes:When shoreline modifications extend into the subtidal, we see differences in juvenile salmonids.
0
0.05
0.1
0.15
0.2
0.25
CobbleBeach
SandBeach
Rip-Rap Deep Rip-Rap
OverwaterStructure
Fish
# /
(Sec
chi d
epth
(m)*
Tran
sect
leng
th(m
))
Other SalmonidGroupings
Chum
Chinook/Chum
Chinook/Coho
Chinook
44
12
879
*
*
*
**
Overwater Structure
Deep Rip-Rap
Rip-Rap
Sand Beach
ChumChinook/
CohoChinook/
ChumChinook
21
4
195
998
249 415
203
79
291
518
1380
38
38
77
309
2103
Cobble Beach
Salmon Locations in Water Column:Deep Rip-Rap and Overwater Structures can affect positions.
surface
middle
bottom
Fish Location:Juvenile salmonids found 70% > 1m away from edge, or 30% at edge, rare underneath Overwater Structures.
23.7 b5.4 bc4.4 c3.4 dOverwater Structure
27.5 a5.9 c2.4 b4.8 dDeep Rip-Rap
28.8 a4.7 a1.7 a7.7 cRip-Rap
28.7 a4.8 ab1.7 a12.9 bSand Beach
28.7 a4.3 a1.6 a17.2 aCobble Beach
Surface Salinity
(ppt)
Average Secchi
Depth (m)
Average Water
Depth at Fish (m)
Average Transect Distance
from Shore (m)Habitat Type
Habitat Measurements:Shoreline modifications truncate the shallow water zone, gradual slope is lost. Pelagic fish that are typically spread-out along a large area may be forced to inhabit deep water directly along shore.
low tide
Sand Beach
Cobble Beach
Rip-Rap
DeepRip-Rap
OverwaterStructure
Diet Analysis:Gastric lavage of juvenile chinook shows less terrestrial/riparian input (insects) at sites with retaining structures at intertidal or supratidal.
0
20
40
60
80
100
Unretained(n=26)
Retained -Supratidal
(n=13)
Retained - HighIntertidal
(n=40)
% IR
I
Other
Terrestrial Riparian
Supralittoral/Marsh
Plant Matter
MarinePlanktonic/Neritic
MarineBenthic/Epibenthic
Overwater Structure
Deep Rip-Rap
Rip-Rap
Sand Beach
ChumChinook/ Coho
Chinook/ ChumChinook
21
4
195
998
249 415
203
79
291
518
1380
38
38
77
309
2103
Cobble Beach
Salmon Behaviors:Mostly schooling or swimming away. Fish are feeding on neuston at modified habitats, but getting less terrestrial input = limited.
Prey Resources:Unretained shorelines have a greater input of terrestrial insects into the diets of juvenile chinook salmon.
Timing and Size:- As compared to Lake Washington: juvenile chinook avoid
armored banks (Roger Tabor).- Juvenile chinook are larger and more pelagic in marine
waters, less dependent on shallow water (Casey Rice).- Differences are related more to indirect rather than direct
effects of shoreline modifications, such as changes in water depth, substrate, and shoreline vegetation.
0
0.03
0.06
0.09
0.12
0.15
0.18
5/19 6/2 6/16 6/30 7/14 7/28Date
Sum
Den
sity
(#/m
3 )
Chum
Coho(unmarked)
Coho(marked)
Chinook(unmarked)
Chinook(marked)
0
40
80
120
160
200
5/19 6/3 6/18 7/3 7/18 8/2Date
Fork
leng
th (m
m)
Coho -marked
Coho -unmarked
Chinook -marked
Chinook -unmarked
Chum
Concluding Remarks:- Shoreline modifications have the greatest effect on marine nearshore fish
communities when they extend from the supratidal through the subtidal.- Cumulative effects could be important, as 84-97% of the shoreline is
modified by retaining structures.
Future Research:- Further examine the effects of shoreline modifications on ecological
communities in regard to bank type, tidal height, and salinity regimes.- Look at landscape level patterns, especially in areas with high degrees of
alteration.- Investigate specific characteristics of Overwater Structures, such as
density, size, distance extending from shore, height above water, etc.
low tide
e-mail: tofty@u.washington.edu Pilot Study Report #301: www.fish.washington.edu/Publications/frireps.htmlFinal Report: due March 30, 2004Ongoing Research:
1. Ferry Terminals2. Monitoring of Salmon Bay Natural Area
Thanks: Funding by Seattle Public Utilities Department (Judith Noble, Gail Arnold Coburn, Julie Hall, Keith Kurko, Ed Connor, Maggie Glowacki, Albert Ponio); Casey Rice for fish permits; stellar fieldcrew (Lia Stamatiou, Carl Young, Danielle Potter, Katie Dodd, Trina Miller, Mike Cooksey, Kathryn Sobocinski, Mark Stamey); Scott Wilson and The North Beach Club for beach access.
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