David B. Rudders William D. DuPaul Jessica Bergeron Virginia Institute of Marine Science Sea Scallop Plan Development Team Warwick, RI January 5, 2012
2011 VIMS-Industry Cooperative Surveys The 2011 Campaign
2011 VIMS-Industry Cooperative Surveys Primary Project Objectives • Assess the abundance and distribution of scallops in selected areas. GBCAII (Access Area) – – DelMarVa Closed Area – Southern New England/Long Island – New York Bight • Determine the inshore extent of the scallop resource in the open areas surveyed. • Estimate exploitable biomass – Biomass of scallops available for capture with 4 inch ring commercial dredge.
2011 VIMS-Industry Cooperative Surveys Secondary Project Objectives • Gear performance • Estimate size selectivity and relative performance of 4.0 ring turtle CFTDD. • Effect of sand dollars on the relative performance of the NMFS survey dredge. • Scallop Biology & Product Quality • Spatially and temporally explicit shell height:meat weight relationship. • Assess metrics associated with product quality. • Finfish Bycatch • By utilizing a commercial dredge we can get a snapshot of finfish bycatch rates and species assemblages in the surveyed areas.
2011 VIMS-Industry Cooperative Surveys Survey Design • Stations: – Systematic design (grid) with random start point – Extent of open area surveys was determined by NMFS shellfish strata and VMS – SNE/LI (15 to 30 fathoms) – NYB (15 to 25 fathoms) • 15 minute tow time • 3.8-4.0 kt. tow speed • 3:1 scope
2011 VIMS-Industry Cooperative Surveys Sampling Gear Coonamessett Farm Turtle NMFS Sea Scallop Survey Dredge Deflector Dredge • 8 ft. width • 2 inch rings • 15 ft. or 14 ft. width • 1.5 inch liner • 4 inch rings • 3.5 inch twine top • No liner • No chains in the areas surveyed • 10 inch twine top • Turtle excluder chains
2011 VIMS-Industry Cooperative Surveys Sampling Protocol • Standard sampling protocol • Sample scallops for length frequency (sub-sample depending upon total volume) • Sample finfish for length frequency • Volumetric measure of trash • Samples for SH:MW • Assessment of product quality parameters
2011 VIMS-Industry Cooperative Surveys Analytical Framework • Area swept per tow • Navigational info • Tilt sensor • Catch weight per tow • Length frequencies • Length-weight relationship CatchWtper TowinSubar ea j • Selectivity (Yochum and DuPaul, 2008) AreaSweptp erTow TotalBioma ss SubArea • Efficiency (constant) j Efficiency j • Values from SARC 2010 – 60%, 65% Commercial Dredge – 38% , 44% NMFS Survey Dredge • Sub-Area (constant) • GBCAII- 3,865 km^2 • DMV- 4,472 km^2 (<50 fathoms) • SNE/LI- 11,203 km^2 • NYB- 7,634 km^2
2011 VIMS-Industry Cooperative Surveys Area Swept • An accurate assessment of tow path is essential to calculate area swept by the gear. • Two tools help with this. – Tilt sensor – High-resolution navigational data Tow Begins Tow Ends • We can measure what the dredge is doing in time and space. With this tow distance is estimated. Depth
2011 VIMS-Industry Cooperative Surveys SH:MW Relationship For each survey, ~250 SH:MW samples were taken. (25 stations @~12/station). Average depth was calculated for each tow from tilt sensor A GLMM was used to fit model (Gamma distribution, log link, random effect at the station level) with SAS PROC GLIMMIX. For all of the VIMS estimates, depth was significant factor with respect to calculated meat weights (Table 9 in report).
2011 VIMS-Industry Cooperative Surveys SH:MW Results – Closed Areas Georges Bank Closed Area II DelMarVa Closed Area 120 120 SARC 2010 - GB General SARC 2010 - MA General SARC 2010 - CA2 Specific VIMS Sept. 2011 - Depth Weighted 100 VIMS May 2011 GBCA2 - Depth Weighted 100 80 Meat Weight (g) 80 Meat Weight (g) 60 60 40 40 20 20 0 0 0 50 100 150 200 0 50 100 150 200 Shell Height (mm) Shell Height (mm) • Georges Bank Closed Area II • Significantly lighter meats relative to the depth weighted SARC relationship. • Something going on in GBCAII (observed by Cfarm Bycatch Survey)? • Both SARV curves are similar. • DelMarVa Closed Area • Heavier meats than the SARC relationship • The difference was focused on the shell heights that contained most of the resource.
2011 VIMS-Industry Cooperative Surveys SH:MW Results – Open Areas Southern New England/Long Island New York Bight 160 160 SARC 2010-MA General SARC 2010 MA General VIMS June 2011 SNE/LI - Depth Weighted 140 140 VIMS Sept. 2011 NYB - Depth Weighted 120 120 Meat Weight (g) 100 100 Grams 80 80 60 60 40 40 20 20 0 0 0 50 100 150 200 0 50 100 150 200 Shell Height (mm) Shell Height (mm) • Southern New England/Long Island • Significantly heavier meats relative to the depth weighted SARC relationship (25% @ 100mm). • Possible driver of high landings? • New York Bight • Heavier meats than the SARC relationship • The difference was focused on the shell heights that contained most of the resource.
2011 VIMS-Industry Cooperative Surveys Length Frequency-Closed Areas DMV GBCAII 7000 1600 Survey Dredge Survey Dredge Commercial Dredge 1400 Commercial Dredge 6000 1200 5000 1000 Frequency Frequency 4000 800 3000 600 2000 400 1000 200 0 0 0 20 40 60 80 100 120 140 160 180 200 0 20 40 60 80 100 120 140 160 180 200 Shell Height (mm) Shell Height (mm) • Georges Bank Closed Area II • dominated by large older animals ~140 mm. • very little recruitment (<70 mm) • sampled roughly 86,000 animals. • DelMarVa Closed Area • dominated by ~120 mm animals • Some sign of recruitment which was spatially limited (E portion of the area). • sampled roughly 13,000 animals
2011 VIMS-Industry Cooperative Surveys Length Frequency-Open Areas SNE/LI NYB 4000 2500 Survey Dredge Survey Dredge Commercial Dredge Commercial Dredge 2000 3000 Frequency Frequency 1500 2000 1000 1000 500 0 0 0 20 40 60 80 100 120 140 160 180 200 0 50 100 150 200 Shell Height (mm) Shell Height (mm) • Southern New England/Long Island • dominated by animals ~120 mm, although multiple adult year classes observed. • very little recruitment • sampled roughly 34,000 animals • New York Bight • dominated by large ~140 mm animals, although abundance was fairly low and very patchy. • very little recruitment which was spatially limited. • sampled roughly 13,000 animals.
2011 VIMS-Industry Cooperative Surveys Scallop Distribution-GBCAII • Georges Bank Closed Area II (catches from the survey dredge) • Most of the resource was located in the South and East of the area. • Large scallop catches in the deeper waters in the East of the area had thin shells and relatively small meats. • very little recruitment (<70 mm).
2011 VIMS-Industry Cooperative Surveys Scallop Distribution-DMV • DelMarVa Closed Area (catches from the survey dredge) • Most of the resource was located in the South and East of the area. • The majority of the catches were less than 100 animals (<1 bushel). • Some observed recruitment (<70 mm) focused mainly in the SE portion of the area.
2011 VIMS-Industry Cooperative Surveys Scallop Distribution-SNE/LI • Southern New England/Long Island (catches from the survey dredge) • Most of the resource was located in the western portion of the sampled area (W. of Montauk). • Scallop abundance was widespread and consistent over a large area. • Some observed recruitment (<70 mm) focused mainly in the western portion of the area.
2011 VIMS-Industry Cooperative Surveys Scallop Distribution-NYB • New York Bight (catches from the survey dredge) • Most of the resource was located in the eastern portion of the sampled area (East of ~20 fathoms). • Scallop abundance was consistently low over a large area. • Some observed recruitment (<70 mm) focused mainly in the eastern portion of the area.
2011 VIMS-Industry Cooperative Surveys Scallop Density
2011 VIMS-Industry Cooperative Surveys Estimated Total Number
2011 VIMS-Industry Cooperative Surveys Mean Scallop Weight
2011 VIMS-Industry Cooperative Surveys Total Biomass
2011 VIMS-Industry Cooperative Surveys Exploitable Biomass
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