Where the Wild Quahogs Are: Looking at Quahog Larval Supply
and Distribution in the Upper Narragansett Bay
Dale Leavitt, M...
An Assessment of Quahog Larval Supply and Distribution in the
Upper Narragansett Bay with a Focus on Spawning Sanctuaries
...
The Big Picture
• Often thought that the quahog
supply in NarBay originated in
the Providence River and
upper bay.
• Resea...
Southern New England Collaborative
Research Initiative (SNECRI)
• NOAA funding became available through
• CFRF Directors d...
An assessment of quahog larval supply and distribution in the
upper Narragansett Bay with a focus on spawning sanctuaries
...
An assessment of quahog larval supply and distribution in the
upper Narragansett Bay with a focus on spawning sanctuaries
...
Develop a cooperative assessment of quahog standing stock in the upper
Narragansett Bay with commercial fishermen.
– Devel...
Area sampled with a bullrake?
• Width
– 15”
• Tooth length
– 1.5” to 3”
• Length of
sample track?
– That’s a problem!
• Wi...
Bullrake calibration with dGPS
• Global Positioning Service (GPS)
– Routinely good to locate within 10 meters (~30 feet)
–...
Land-based calibration
Accuracy of dGPS to measure linear
distance?
Measuring linear distance on the water
Bullrake transects with dGPS at stale
Transect Method
Diver
Measured
transect
length (m)
Estimated
transect
length using
dGPS (m)
Difference
between
measured
an...
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 10 20 30 40 50 60
Amountoferrorinmeasuringtransectlength(m)
Angle of deflection from...
Transect Method
Diver
Measured
transect
length (m)
Estimated
transect
length using
dGPS (m)
Difference
between
measured
an...
Bullrake Catch Efficiency
Transect Quahogger Location substrate
Quahogs
caught
Quahogs
missed
catch
efficiency Comments
1 ...
Transect Locations Fisherman
Substrate
Type
Area
sampled
w/ bullrake
(m2
)
density
measured by
bullrake
(quahogs/m2
)
catc...
Size class distribution
0
2
4
6
8
10
12
14
40
42
44
46
48
50
52
54
56
58
60
62
64
66
68
70
72
74
76
78
80
82
84
86
88
90
9...
– Step 2
• Conduct side-by-side quahog stock assessments between DEM
hydraulic dredge and bullrakers
Develop a cooperative...
Bullrake Stock
Assessment
• Stratified random
sampling protocol
– Sampling within
strata
• Run one 100’
transect per strat...
DEM Dredge Survey Sites - 2013
RI-DEM Tow
ID
Dredge
adjusted for
57.7%
efficiency
Bullrake
adjusted for
90%
efficiency StDev Substrate type
2389 15.36 9....
Discussion with RIDEM – Marine
Fisheries
• Looks like a bullrake is a viable stock assessment tool.
– If the dredge catch ...
Quahog Reproduction
• Some attempts to
manage areas for quahog
reproduction
– Areas with high numbers
of quahogs that allo...
Reproductive effort study
• Selected 8 sites for
long-term
sampling
• Sample 2x per
month
• Assess for gonad
condition, i....
Reproductive Condition of Quahogs: Efficacy of Transplants
• 2012
– Condition Index & Gonad
Index at 8 sites
• Sample ever...
Reproductive Condition of Quahogs
Preliminary Results
 Significantly lower
mean CI in closed sites
 2012 and 2013 fall
g...
Recruitment
• Based on our stock
surveys and
consultation with
quahoggers, we know
where there are high
concentrations of
...
An assessment of quahog larval supply and distribution in the
upper Narragansett Bay with a focus on spawning sanctuaries
...
Objectives of this portion of
talk:
• Describe results of particle tracking
simulations in Narragansett Bay for
the purpos...
Model Domains:
•Low resolution
•Nested high
resolution
Realistically-Forced
Circulation Model
Nested (ROMS) configuration:...
2006 2007
Environmental Forcing During Simulated Years
Obs. Surface
Model Surface
Obs. Bottom
Model Bottom
Salinity
Temperature
ROMS Model-Data Comparison: T/S at Conimicut
Larval Tracking Model
Larval dispersal modeled with Lagrangian TRANSport model
(LTRANS) developed by E. North and collabor...
Example trajectory
simulations:
• Clusters of 65 particles
released every hour for 6
hours.
• Particles tracked over 24
ho...
Example trajectory
simulations:
• Clusters of 65 particles
released every hour for 6
hours.
• Particles tracked over 24
ho...
Passive Particles, Spatial Distributions after 10 Days
Particles Released
From Providence
River Site
2006: 34% lost 2007: ...
Passive Particles, Spatial Distributions after 10 Days
2006: 51% lost 2007: 45% lost
Particles Released
From GB Spawner
Sa...
Passive Particles, Spatial Distributions after 10 Days
2006: 21% lost 2007: 11% lost
Particles Released
From Greenwich
Cov...
Passive Particles, Spatial Distributions after 10 Days
2006: 95% lost 2007: 96% lost
Particles Released
From Rome Point
Si...
Passive Particles, Spatial Distributions after 10 Days
2006: 46% lost 2007: 35% lost
Particles Released
From Hog Island
Si...
Passive Particles, Spatial Distributions after 10 Days
2006: 43% lost 2007: 34% lost
Particles Released
From Rocky Point
S...
Larval Behavior
Hard clam larvae:
• Planktonic stage lasts 1-2 weeks (T dependent).
• Swim upward early in planktonic peri...
Passive versus Active Particles, Spatial Distributions after 10 Days
2007, Passive: 20% lost 2007, Active: 53% lost
Partic...
An assessment of quahog larval supply and distribution in the
upper Narragansett Bay with a focus on spawning sanctuaries
...
Hog Island 5/31—6/4, 2012 Spawner Sanctuary 6/18—6/24, 2012
9% lost
Providence River Model Providence River Drifters
34% lost
Rocky Point Model Rocky Point Drifters
Spawner Sanctuary Model Spawner Sanctuary Drifters
45% lost
96% lost
Rome Point Model Rome Point Drifters
35% lost
Hog Island Model Hog Island Drifters
46% lost
(2006)
Looking for the larvae
Name Lat Long
Anticipated
larval
supply
Greenwich Cove 41.661637 -71.442319 High
Chepiwanoxet 41.67...
An assessment of quahog larval supply and distribution in the
upper Narragansett Bay with a focus on spawning sanctuaries
...
What next?
• Will continue to work with the quahog fishing
fleet and RIDEM Marine Fisheries to integrate
bullraking into t...
Questions?
Where the Wild Quahogs Are: Looking at Quahog Larval Supply and Distribution in the Upper Narragansett Bay
Where the Wild Quahogs Are: Looking at Quahog Larval Supply and Distribution in the Upper Narragansett Bay
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Where the Wild Quahogs Are: Looking at Quahog Larval Supply and Distribution in the Upper Narragansett Bay

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Where the Wild Quahogs Are: Looking at Quahog Larval Supply and Distribution in the Upper Narragansett Bay presented at April 14th, 2014 Rhode Island Shellfish Management Plan Stakeholder meeting by Dale Leavitt, Matt Griffin, Scott Rutherford (RWU), and Chris Kincaid and Dave Ullman (URI).

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Where the Wild Quahogs Are: Looking at Quahog Larval Supply and Distribution in the Upper Narragansett Bay

  1. 1. Where the Wild Quahogs Are: Looking at Quahog Larval Supply and Distribution in the Upper Narragansett Bay Dale Leavitt, Matt Griffin & Scott Rutherford – RWU Chris Kincaid & Dave Ullman – URI
  2. 2. An Assessment of Quahog Larval Supply and Distribution in the Upper Narragansett Bay with a Focus on Spawning Sanctuaries and Alternative Area Management Strategies Dale Leavitt, Matt Griffin & Scott Rutherford – RWU Chris Kincaid & Dave Ullman – URI
  3. 3. The Big Picture • Often thought that the quahog supply in NarBay originated in the Providence River and upper bay. • Research effort originated with discussions among CFRF, RISA, RWU and DEM Marine Fisheries (2010) • With increased fishing pressure in Areas A & B (resulting from, NBC’s CSO Project) and Greenwich Bay – how would that affect quahog resources?
  4. 4. Southern New England Collaborative Research Initiative (SNECRI) • NOAA funding became available through • CFRF Directors dedicated funding to assist in expanding our knowledge of quahog dynamics in the bay • In 2011, the project was started to address some of the questions proposed in discussions with DEM Marine Fisheries
  5. 5. An assessment of quahog larval supply and distribution in the upper Narragansett Bay with a focus on spawning sanctuaries and alternative area management strategies. • Develop a cooperative assessment of quahog standing stock and reproductive condition in the upper NarBay with commercial fishermen – Conduct side-by-side quahog stock assessments comparing the efficacy of the RI DEM’s standard method (hydraulic dredge) with the commercial bullrake and diver quadrat sampling • Through the application of the ROMS Hydrodynamic Model for NBay, simulate specific quahog larval release points (spawning areas) based on stock assessments and predict sites of juvenile recruitment resulting from these releases • Using the results of the model, validate predicted larval settlement sites through a combined effort of surface drifter deployments and monitoring for the occurrence of quahog larvae • Apply the prediction of quahog larval sources and sinks to the development of a state-wide shellfish management plan currently under discussion among RI-DEM, CRMC, CRC, and others.
  6. 6. An assessment of quahog larval supply and distribution in the upper Narragansett Bay with a focus on spawning sanctuaries and alternative area management strategies. • Develop a cooperative assessment of quahog standing stock and reproductive condition in the upper NarBay with commercial fishermen – Conduct side-by-side quahog stock assessments comparing the efficacy of the RI DEM’s standard method (hydraulic dredge) with the commercial bullrake and diver quadrat sampling • Through the application of the ROMS Hydrodynamic Model for NBay, simulate specific quahog larval release points (spawning areas) based on stock assessments and predict sites of juvenile recruitment resulting from these releases • Using the results of the model, validate predicted larval settlement sites through a combined effort of surface drifter deployments and monitoring for the occurrence of quahog larvae • Apply the prediction of quahog larval sources and sinks to the development of a state-wide shellfish management plan currently under discussion among RI-DEM, CRMC, CRC, and others.
  7. 7. Develop a cooperative assessment of quahog standing stock in the upper Narragansett Bay with commercial fishermen. – Develop improved stock assessment protocols • The ultimate goal is to have RI quahoggers conduct their own stock assessment, in collaboration with DEM Marine Fisheries – Step 1 • Bullrake sampling – Want to compare the effectiveness of a bullrake to other stock assessment methods – Diver sampling is highest standard • How? – Measure exact area that a bullrake samples » Need to know width and length of sample track – Count the number of quahogs and measure their size
  8. 8. Area sampled with a bullrake? • Width – 15” • Tooth length – 1.5” to 3” • Length of sample track? – That’s a problem! • With the rake at the end of a rigid pole, can we measure the distance the handle travels as a proxy for the distance the rake travels?
  9. 9. Bullrake calibration with dGPS • Global Positioning Service (GPS) – Routinely good to locate within 10 meters (~30 feet) – Usually okay for navigation but… • Differential GPS – Utilizes a base station to increase accuracy – Can be accurate to within 10 cm (4 in) • Attach dGPS to a bullrake – Can track the movement of the rake across the bottom
  10. 10. Land-based calibration
  11. 11. Accuracy of dGPS to measure linear distance?
  12. 12. Measuring linear distance on the water
  13. 13. Bullrake transects with dGPS at stale
  14. 14. Transect Method Diver Measured transect length (m) Estimated transect length using dGPS (m) Difference between measured and dGPS % Difference between measured and dGPS 2-1 continuous 14.17 19.48 5.31 37.5% 2-2 continuous 15.54 14.52 -1.02 -6.6% 2-3 continuous 18.59 24.81 6.22 33.5% 2-4 continuous 15.54 14.61 -0.93 -6.0% 3-1 start/stop 8.69 7.03 -1.66 -19.1% 4-1 start/stop 13.41 15.75 2.34 17.4% 4-2 start/stop 13.26 15.50 2.24 16.9% 4-3 start/stop 12.68 12.62 -0.06 -0.5% 5-1 start/stop 29.57 30.32 0.75 2.5% 5-2 start/stop 29.26 29.16 -0.10 -0.3% 5-3 start/stop 28.96 29.66 0.70 2.4% 5-4 start/stop 27.58 28.25 0.67 2.4% 5-5 start/stop 15.41 15.79 0.38 2.5% 6-1 start/stop 21.03 20.40 -0.63 -3.0% 6-2 start/stop 20.42 19.63 -0.79 -3.9% 6-3 start/stop 28.96 28.51 -0.45 -1.6% average 0.07 0.1% stdev 0.64 2.7% Diver-measured bullrake transect length compared to that observed using post-processed dGPS data.
  15. 15. 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 10 20 30 40 50 60 Amountoferrorinmeasuringtransectlength(m) Angle of deflection from transect line (degrees) 4 m stale with 24 m transect 8 m stale with 24 m transect 14 m stale with 24 m transect 4 m stale with 30 m transect 8 m stale with 30 m transect 14 m stale with 30 m transect Error due to stale angle off from transect direction
  16. 16. Transect Method Diver Measured transect length (m) Estimated transect length using dGPS (m) Difference between measured and dGPS % Difference between measured and dGPS 2-1 continuous 14.17 19.48 5.31 37.5% 2-2 continuous 15.54 14.52 -1.02 -6.6% 2-3 continuous 18.59 24.81 6.22 33.5% 2-4 continuous 15.54 14.61 -0.93 -6.0% 3-1 start/stop 8.69 7.03 -1.66 -19.1% 4-1 start/stop 13.41 15.75 2.34 17.4% 4-2 start/stop 13.26 15.50 2.24 16.9% 4-3 start/stop 12.68 12.62 -0.06 -0.5% 5-1 start/stop 29.57 30.32 0.75 2.5% 5-2 start/stop 29.26 29.16 -0.10 -0.3% 5-3 start/stop 28.96 29.66 0.70 2.4% 5-4 start/stop 27.58 28.25 0.67 2.4% 5-5 start/stop 15.41 15.79 0.38 2.5% 6-1 start/stop 21.03 20.40 -0.63 -3.0% 6-2 start/stop 20.42 19.63 -0.79 -3.9% 6-3 start/stop 28.96 28.51 -0.45 -1.6% average 0.07 0.1% stdev 0.64 2.7% Diver-measured bullrake transect length compared to that observed using post-processed dGPS data.
  17. 17. Bullrake Catch Efficiency Transect Quahogger Location substrate Quahogs caught Quahogs missed catch efficiency Comments 1 A off Allen's Harbor sand 19 3 86.4% 2 A off Allen's Harbor sand 21 7 75.0% 3 A off Allen's Harbor sand 24 11 68.6% 4 A off Allen's Harbor sand 52 3 94.5% 5 A off Allen's Harbor sand 46 2 95.8% 6 A off Allen's Harbor sand 39 2 95.1% 7 A off Allen's Harbor sand 46 3 93.9% 8 B Oakland Beach sand 24 14 63.2% inexperienced divers 9 C Rocky Point sand 129 14 90.2% 10 C Rocky Point sand 115 12 90.6% 11 C Rocky Point sand 80 15 84.2% bottom hardened up 12 C Chepwenoxit mud 20 2 90.9% 13 C Chepwenoxit mud 50 2 96.2% 14 C Chepwenoxit mud 57 1 98.3% 15 C Chepwenoxit mud 129 8 94.2% 16 C Chepwenoxit mud 97 9 91.5% 17 D Sally's Rock mud 27 3 90.0% 18 D Sally's Rock mud 9 4 69.2% rake jumped on rock 19 D Sally's Rock mud 14 3 82.4% shell on tooth 20 D Rocky Point sand 48 1 98.0% 21 D Rocky Point sand 71 4 94.7% sand avg 89.3% average 90.8% mud avg 93.5% stdev 7.9%
  18. 18. Transect Locations Fisherman Substrate Type Area sampled w/ bullrake (m2 ) density measured by bullrake (quahogs/m2 ) catch efficiency total density (adjusted for avg efficiency) (quahogs/m2 ) avg density measured by diver quadrat (quahogs/m2 ) Bullrake density - Diver density (quahogs/m2 ) 2-1 Allen's Hbr A sand-mud 6.66 7.81 94.5% 8.35 8.00 0.35 2-2 Allen's Hbr A 7.30 6.30 95.8% 6.73 7.00 -0.27 2-3 Allen's Hbr A 8.74 4.46 95.1% 4.77 4.00 0.77 2-4 Allen's Hbr A 7.30 6.30 93.9% 6.73 6.33 0.40 4-1 Rocky Point C sand 8.40 15.35 90.2% 16.41 8.00 8.41 4-2 Rocky Point C 8.27 13.91 90.6% 14.87 13.00 1.87 5-1 Chepwenoxit C soft mud 16.94 1.18 90.9% 1.26 6.00 -4.74 5-2 Chepwenoxit C 16.30 3.07 96.2% 3.28 3.50 -0.22 5-3 Chepwenoxit C 16.53 3.52 98.3% 3.76 5.00 -1.24 5-4 Chepwenoxit C 16.57 7.97 94.2% 8.52 6.00 2.52 5-5 Chepwenoxit C 15.79 6.29 91.5% 6.72 8.50 -1.78 6-1 Sally's Rock D soft mud 9.33 2.90 90.0% 3.10 3.33 -0.23 7-2 Rocky Point D sand 7.16 8.74 94.7% 9.34 7.50 1.84 overall average 93.5% 7.22 6.63 0.59 standard deviation 2.6% 4.45 2.58 2.99 93.6% 9.60 7.69 1.91 2.2% 4.39 2.72 2.97 93.5% 4.44 5.39 -0.95 3.3% 2.67 1.92 2.38 on sand SD on mud SD Quahog density measured by diver compared to that measured by bullrake
  19. 19. Size class distribution 0 2 4 6 8 10 12 14 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104 106 108 110 Numberofindividuals Length Intervals (mm) Littleneck Cherrystone ChowderSub-legal
  20. 20. – Step 2 • Conduct side-by-side quahog stock assessments between DEM hydraulic dredge and bullrakers Develop a cooperative assessment of quahog standing stock and reproductive condition in the upper NarBay with commercial fishermen
  21. 21. Bullrake Stock Assessment • Stratified random sampling protocol – Sampling within strata • Run one 100’ transect per strata – Annually
  22. 22. DEM Dredge Survey Sites - 2013
  23. 23. RI-DEM Tow ID Dredge adjusted for 57.7% efficiency Bullrake adjusted for 90% efficiency StDev Substrate type 2389 15.36 9.37 2.22 hard bottom 2393 0.80 0.12 0.11 hard bottom 2424 20.19 13.73 6.87 very hard bottom 2429 3.29 8.05 4.60 moderate hard bottom 2445 0.43 0.77 0.70 soft mud 2448 6.40 6.63 3.99 soft sticky mud 2453 0.80 0.43 0.33 soft sticky mud 2484 0.47 3.21 2.13 soft sticky mud w/ shell 2485 5.13 11.80 6.41 hard w/ shells 2496 4.54 10.37 1.74 moderate hard bottom GB adjacent 1.11 1.99 1.07 soft mud w/ shell average 5.32 6.04 stdev 6.59 4.95 Bullrake – DEM Dredge comparison
  24. 24. Discussion with RIDEM – Marine Fisheries • Looks like a bullrake is a viable stock assessment tool. – If the dredge catch efficiency is factored in – then the two techniques appear to measure quahog density similarly. – Can we improve on the technique? • What more do we need to do to confirm this observation? – How many samples are required? • Is there a role for quahoggers to assist in stock assessment? – How many samples would be needed to “calibrate” a quahogger? • If it works, how do we make it happen? – Starting during summer 2014 – quahoggers may be used to sample shallow coves where dredge can not sample.
  25. 25. Quahog Reproduction • Some attempts to manage areas for quahog reproduction – Areas with high numbers of quahogs that allow for intensive reproduction • Spawning Sanctuaries • Closed areas • May be problematic – Quahogs in protected areas may not be spawning!!!! Marroquin-Mora & Rice (2008)
  26. 26. Reproductive effort study • Selected 8 sites for long-term sampling • Sample 2x per month • Assess for gonad condition, i.e. reproductive status Site Lat Lon Density Fishing Status *Bissel Cove 41 32.520 71 25.164 Low Open *Greenwich Cove 41 40.160 71 26.529 High Closed *Spawner Sanctuary 41 40.050 71 23.630 Med Closed *Rocky Pt. 41 41.940 71 21.111 Med Open *Providence River 41 45.650 71 22.030 High Closed Conditional Area B 41 40.475 71 20.370 Low Conditional Prudence Island 41 38.055 71 19.622 Med/High Open *Hog Island 41 38.136 71 16.689 Low Open
  27. 27. Reproductive Condition of Quahogs: Efficacy of Transplants • 2012 – Condition Index & Gonad Index at 8 sites • Sample every 3 weeks • Open, closed & sanctuary – Mark/Recapture experiment • Tag 1,600 quahogs from Greenwich Cove • Transplant to Spawning Sanctuary • 2013 – Repeat 2012 (April – November) – Mark-Recapture experiment • Sample every 3 weeks (April – November) • Condition Index & Gonad Index
  28. 28. Reproductive Condition of Quahogs Preliminary Results  Significantly lower mean CI in closed sites  2012 and 2013 fall gonad recovery different 60 70 80 90 100 110 120 130 140 150 10-Apr-12 30-May-12 19-Jul-12 7-Sep-12 27-Oct-12 MeanConditionIndex Open Sanctuary Closed 60 70 80 90 100 110 120 130 140 150 10-Apr-13 30-May-13 19-Jul-13 7-Sep-13 27-Oct-13 MeanConditionIndex Open Sanctuary Closed 2012 2013
  29. 29. Recruitment • Based on our stock surveys and consultation with quahoggers, we know where there are high concentrations of reproductive quahogs • However, what happens to the quahog larvae following gamete release? Providence River Rocky Point DEM Spawning Sanctuary Hog Island Greenwich Cove Bissel Cove
  30. 30. An assessment of quahog larval supply and distribution in the upper Narragansett Bay with a focus on spawning sanctuaries and alternative area management strategies. • Develop a cooperative assessment of quahog standing stock and reproductive condition in the upper NarBay with commercial fishermen – Conduct side-by-side quahog stock assessments comparing the efficacy of the RI DEM’s standard method (hydraulic dredge) with the commercial bullrake and diver quadrat sampling • Through the application of the ROMS Hydrodynamic Model for NBay, simulate specific quahog larval release points (spawning areas) based on stock assessments and predict sites of juvenile recruitment resulting from these releases • Using the results of the model, validate predicted larval settlement sites through a combined effort of surface drifter deployments and monitoring for the occurrence of quahog larvae • Apply the prediction of quahog larval sources and sinks to the development of a state-wide shellfish management plan currently under discussion among RI-DEM, CRMC, CRC, and others.
  31. 31. Objectives of this portion of talk: • Describe results of particle tracking simulations in Narragansett Bay for the purpose of evaluating the dispersal of planktonic quahog larvae. • Demonstrate the important effect of larval behavior (vertical swimming) on dispersal in the Bay.
  32. 32. Model Domains: •Low resolution •Nested high resolution Realistically-Forced Circulation Model Nested (ROMS) configuration: • Low resolution model extending onto continental shelf provides boundary conditions for high- resolution Bay model. • Curvilinear grid with resolution of 50-100m in upper Bay. • Sigma vertical coordinate (15 levels). • Forced with measured river inflows and surface fluxes and tides from ADCIRC (NOAA). • Simulate 45 day period (May 15-June 30, 2007).
  33. 33. 2006 2007 Environmental Forcing During Simulated Years
  34. 34. Obs. Surface Model Surface Obs. Bottom Model Bottom Salinity Temperature ROMS Model-Data Comparison: T/S at Conimicut
  35. 35. Larval Tracking Model Larval dispersal modeled with Lagrangian TRANSport model (LTRANS) developed by E. North and collaborators (U. Maryland): • 4th order Runga-Kutta advection using ROMS velocities. • Random displacement model, based on ROMS vertical diffusivity simulates effect of vertical turbulence. • Zero horizontal diffusion in our application. • Particles reaching open boundary assumed lost to the system. • Perform simulations without larval behavior (passive particles) and with vertical swimming. Clusters of 65 particles released every 2 hours over a 1 month period at 6 potential sanctuary sites: • Get trajectory simulations under wide range of forcing conditions (e.g. wind, tide, mixing) characteristic of the ~1 month spawning period of hard clams.
  36. 36. Example trajectory simulations: • Clusters of 65 particles released every hour for 6 hours. • Particles tracked over 24 hours (starting at time of 1st release). Illustrates the variability in particle trajectories depending on the time (relative to the tidal cycle) of release.
  37. 37. Example trajectory simulations: • Clusters of 65 particles released every hour for 6 hours. • Particles tracked over 24 hours (starting at time of 1st release). Illustrates the variability in particle trajectories depending on the time (relative to the tidal cycle) of release.
  38. 38. Passive Particles, Spatial Distributions after 10 Days Particles Released From Providence River Site 2006: 34% lost 2007: 20% lost
  39. 39. Passive Particles, Spatial Distributions after 10 Days 2006: 51% lost 2007: 45% lost Particles Released From GB Spawner Sanctuary Site
  40. 40. Passive Particles, Spatial Distributions after 10 Days 2006: 21% lost 2007: 11% lost Particles Released From Greenwich Cove Site
  41. 41. Passive Particles, Spatial Distributions after 10 Days 2006: 95% lost 2007: 96% lost Particles Released From Rome Point Site
  42. 42. Passive Particles, Spatial Distributions after 10 Days 2006: 46% lost 2007: 35% lost Particles Released From Hog Island Site
  43. 43. Passive Particles, Spatial Distributions after 10 Days 2006: 43% lost 2007: 34% lost Particles Released From Rocky Point Site
  44. 44. Larval Behavior Hard clam larvae: • Planktonic stage lasts 1-2 weeks (T dependent). • Swim upward early in planktonic period, downward later. (LTRANS superimposes a degree of randomness on this pattern.) Model swimming behavior: upward downward
  45. 45. Passive versus Active Particles, Spatial Distributions after 10 Days 2007, Passive: 20% lost 2007, Active: 53% lost Particles Released From Providence River Site
  46. 46. An assessment of quahog larval supply and distribution in the upper Narragansett Bay with a focus on spawning sanctuaries and alternative area management strategies. • Develop a cooperative assessment of quahog standing stock and reproductive condition in the upper NarBay with commercial fishermen – Conduct side-by-side quahog stock assessments comparing the efficacy of the RI DEM’s standard method (hydraulic dredge) with the commercial bullrake and diver quadrat sampling • Through the application of the ROMS Hydrodynamic Model for NBay, simulate specific quahog larval release points (spawning areas) based on stock assessments and predict sites of juvenile recruitment resulting from these releases • Using the results of the model, validate predicted larval settlement sites through a combined effort of surface drifter deployments and monitoring for the occurrence of quahog larvae • Apply the prediction of quahog larval sources and sinks to the development of a state-wide shellfish management plan currently under discussion among RI-DEM, CRMC, CRC, and others.
  47. 47. Hog Island 5/31—6/4, 2012 Spawner Sanctuary 6/18—6/24, 2012
  48. 48. 9% lost Providence River Model Providence River Drifters
  49. 49. 34% lost Rocky Point Model Rocky Point Drifters
  50. 50. Spawner Sanctuary Model Spawner Sanctuary Drifters 45% lost
  51. 51. 96% lost Rome Point Model Rome Point Drifters
  52. 52. 35% lost Hog Island Model Hog Island Drifters 46% lost (2006)
  53. 53. Looking for the larvae Name Lat Long Anticipated larval supply Greenwich Cove 41.661637 -71.442319 High Chepiwanoxet 41.676307 -71.442443 High Sandy Point 41.664646 -71.405473 Low Spawning Sanctuary 41.669821 -71.389343 Low Sugar Mountain 41.655645 -71.370999 High Warwick Neck 41.663884 -71.368550 High Hope Island 41.377688 -71.377688 Low
  54. 54. An assessment of quahog larval supply and distribution in the upper Narragansett Bay with a focus on spawning sanctuaries and alternative area management strategies. • Develop a cooperative assessment of quahog standing stock and reproductive condition in the upper NarBay with commercial fishermen – Conduct side-by-side quahog stock assessments comparing the efficacy of the RI DEM’s standard method (hydraulic dredge) with the commercial bullrake and diver quadrat sampling • Through the application of the ROMS Hydrodynamic Model for NBay, simulate specific quahog larval release points (spawning areas) based on stock assessments and predict sites of juvenile recruitment resulting from these releases • Using the results of the model, validate predicted larval settlement sites through a combined effort of surface drifter deployments and monitoring for the occurrence of quahog larvae • Apply the prediction of quahog larval sources and sinks to the development of a state-wide shellfish management plan currently under discussion among RI-DEM, CRMC, CRC, and others.
  55. 55. What next? • Will continue to work with the quahog fishing fleet and RIDEM Marine Fisheries to integrate bullraking into their stock assessment process. • RI Sea Grant has funded continuation of the ROMS modeling effort where we will add more years to the data set to look at annual variability. • Will more closely analyze the reproductive cycle in the quahogs collected in 2012/2013. • Will integrate the results from this study into our baseline knowledge for use in the Shellfish Management Plan.
  56. 56. Questions?

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