David Steven Brown_ Oyster Baselines
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Eastern oyster population ecology and landscape characteristics in Ninigret Pond,
Rhode Island
Brown, D., DeAngelis, B., Stills, B.
The Nature Conservancy (1)
NOA Restoration Center (2)
University of Rhode Island (3)
Project Background
• Global loss in oyster reef habitat and ecological services
• E-NGO, academic, state-federal agency interest in oyster habitat and population enhancement, with complimentary yet conflicting goals, e.g.:– Fisheries enhancement
– Water quality improvement
– Shoreline improvement and resiliency
• Local, state, and regional goals cannot be determined or evaluated without population and ecological baselines
Rhode Island Objectives• Establish restoration baselines and identify needs
• Characterize natural and restored beds
• Identify environmental and biological constraints
General Approach• Standardized assessment and mapping of natural oyster beds
• Population inventory and habitat characterization
• Oyster settlement collection and body condition index
• Larval presence and density
Case Site – Ninigret (Charlestown Pond)
• Largest coastal lagoon
– Pond area: 7.38 km-2
– Watershed area: 6,000 acres
– Mean depth: 1.31 m
– Tidal fluctuations: 7-16 cm (Bothroyd et al., 1985)
• Historical collapse of oyster reefs (Lee, 1980; Simpson, 1977)
– Permanent breach way increased sedimentation, increased salinity
• Rise in oyster aquaculture (3.8 acres under cultivation, 2011)
• Wild stock estimated at 24,200 (Ganz et al., 1984)
Oysterscape
Rock reef, mudRip-rap
Rock reef, sand
Sand-cobble, shoal
Sand bar reef
Rip-rap
Sand-cobble, shoal
Sand bar reef
Rip-rap
Sand-cobble, shoal
Populations delineated by d-GPS. Outer bounds are smoothed by 0.1-m and represent areas with oyster densities greater than 5 m-2
Substrate Preferences
A. Sand-cobble aggregate
B. Sand-shell aggregate
C. Rip-rap revetment
Sand-
shell
Sand-c
obbl
e
Roc
k
Rip-r
ap
160
140
120
100
80
60
40
20
0
San
d-sh
ell
San
d-co
bble
Roc
k
Rip-r
ap
Live (m)
Substrate
Dead (m)
A, B
A
C A
B
A
GLM: F = 5.1, p = 0.034GLM: F= 9.2, p = 0.001
D. Rock
Substrate Preferences
A. Sand-cobble aggregate
B. Sand-shell aggregate
C. Rip-rap revetment D. Rock
140
120
100
80
60
40
20
0
16
12
8
4
0
140
120
100
80
60
40
200
16
12
8
4
0
Cobble
SH (mm)
Fre
qu
en
cy
Rip-rap
Rock Shell
Greater occurrence of adults, decreased harvesting pressure
Substrate Characteristics
A. Sand-cobble aggregate
B. Sand-shell aggregate
C. Rip-rap revetment D. Rock
40
30
20
10
0
SSNEFNFCSSNEFNFC
60
45
30
15
0
LocationSSNEFNFCSSNEFNFC
40
30
20
10
0
Course (%) Sand (%)
Fines (%)
Sand
Shell
Habitat
1-5 mm, * 106-710 µm, *
≤ 106 µm Difference between sand-silt and sand-shell composition (F = 7.8, p <0.05), but no difference between locations (F = 3.17, p > 0.05)
Substrate Characteristics
A. Sand-cobble aggregate
B. Sand-shell aggregate
C. Rip-rap revetment
Location SSNEFNFCSSNEFNFC
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
To
tal
Org
an
ic C
arb
on
, L
OI
(%) Sand
Shell
Habitat
Location F = 32.8, p = 0.01
GLM: Habitat F = 23.6, p =0.04
D. Rock
SSNEFNFC
120
90
60
30
0
SSNEFNFC
Live (m)
Location
Dead (m)
FC
FN
NE
SS
Location
140120100806040200
20
10
0
140120100806040200
20
10
0
Fort Neck
SH (mm)
Fre
qu
en
cy
Foster Cove
Ninigret East
Population Demographics
Greater occurrence of adults, Closed Shellfish Management Area
Wild Oyster Population in Open Shellfish
Management Area (Ninigret Pond, 2011)
Wild Oyster Population in Closed Shellfish
Management Area (Ninigret Pond, 2011)
• Fishing pressure? Disease?
• What is the variation in female
fecundity on effective population size?
Larval and Spat Recruitment
Month
Sept
embe
r
Augu
stJu
lyJu
neMay
Sept
embe
r
Augu
stJu
lyJu
neMay
Sept
embe
r
Augu
stJu
lyJu
neMay
Sept
embe
r
Augu
stJu
lyJu
neMay
Sept
embe
r
Augu
stJu
lyJu
neMay
14
12
10
8
6
4
2
0
Sp
at
(m2
)
FC
FN
GP
NE
SS
LocationWhen does recruitment occur?
Peaks in June, and September
Month
Sept
embe
r
Augu
stJu
lyJu
ne
Sept
embe
r
Augu
stJu
lyJu
ne
Sept
embe
r
Augu
stJu
lyJu
ne
Sept
embe
r
Augu
stJu
lyJu
ne
Sept
embe
r
Augu
stJu
lyJu
ne
Sept
embe
r
Augu
stJu
lyJu
ne
90
80
70
60
50
40
30
20
10
0
Mean
Larv
al D
en
sit
y (
± 1
SE
) / L
Farms
FC
FN
GP
NE
SS
Location
Oyster spat, 16 day
August, AvgWS 4.25
m/s
May, AvgWS 4.91m/s June, AvgWS 4.49 m/s July, AvgWS 4.28 m/s
September, AvgWS 4.27 m/s
Wind driven dispersion
Environmental Constraints
35
30
25
20
15
May
Septem
ber
August
JulyJu
ne
May
25.0
22.5
20.0
17.5
15.0
Month2M
ay
Septem
ber
August
July
June
May
6.0
4.5
3.0
1.5
0.0
10
8
6
4
Salinity (%) Temp (°C)
Chl a (µg/l) DO (mg/l)
FC
FN
GP
NE
SS
Location
Spawning events
Higher settlement at lower salinities
120100806040200
35
30
25
20
15
10
5
Mean Adult Oyster m-2
Me
an
Oyste
r La
rva
e L Farms
FC
FN
GP
NE
SS
Location
Predicted relationship
Biomass DW g/m-2 Area (m-2) Total DW (lbs)
Foster Cove 656 1496 2157
Fort Neck 536 1087 1281
Spawner Sanctuary 519 66 75
Ninigret East 711 982 1535
Total Wild 2422 3631 5047
Aquaculture 1000 15378 33788
Adult/Recruit Relationships
• Oyster larvae is a function of the number of adult broodstock, water retention (hydrology), and substrate quality
• Oyster larvae was present in both Aquaculture and Grassy Point sites which neighbor oyster aquaculture leases and don’t have natural beds
• It appears aquacultured oysters may be a source for wild oyster stocks
• Evaluate larval contribution from
oyster aquaculture to wild stock
• Develop multi-reef framework
• Evaluate population connectivity
and resiliency
Current and Future Goals
• Settlement occurred above sediments,
areas with lower salinity and water
residency times
• Test vertical height, and substrate
type (rugosity)
• Reef Design
• 2/3 surf clam, 1/3 oyster shell
• Veneer – bagged oyster shell
• Base – loose surf clam shell
Evaluate Reef Design
Experimental reefs mimicking natural reef design
through shape, and vertical relief or height.
60 cm bed height
Questions and Thank you!If interested in volunteering for the 2013 reef construction
please let us know!E: dsbrown@tnc.org
P: 860-271-3535
This work is partially funded by:
• USDA NRCS Conservation Technical Assistance
• TNC-NOAA Community Restoration Program
• RI CRMC Habitat Trust Fund
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