David B. Rudders William D. DuPaul Jessica Bergeron Virginia - - PowerPoint PPT Presentation

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

NMFS Sea Scallop Survey Dredge

• 8 ft. width
• 2 inch rings
• 1.5 inch liner
• 3.5 inch twine top
• No chains in the areas surveyed

Coonamessett Farm Turtle Deflector Dredge

• 15 ft. or 14 ft. width
• 4 inch rings
• No liner
• 10 inch twine top
• Turtle excluder chains

• 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

Sampling Protocol

2011 VIMS-Industry Cooperative Surveys

Analytical Framework

j j j

SubArea Efficiency erTow AreaSweptp ea TowinSubar CatchWtper ss TotalBioma



                      

• Area swept per tow
• Navigational info
• Tilt sensor
• Catch weight per tow
• Length frequencies
• Length-weight relationship
• Selectivity (Yochum and DuPaul, 2008)
• Efficiency (constant)
• 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

• 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

• We can measure what the

dredge is doing in time and

• space. With this tow distance

is estimated.

2011 VIMS-Industry Cooperative Surveys

Area Swept

Tow Begins Tow Ends

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

Shell Height (mm)

50 100 150 200

Meat Weight (g)

20 40 60 80 100 120 SARC 2010 - GB General SARC 2010 - CA2 Specific VIMS May 2011 GBCA2 - Depth Weighted

DelMarVa Closed Area

Shell Height (mm)

50 100 150 200

Meat Weight (g)

20 40 60 80 100 120 SARC 2010 - MA General VIMS Sept. 2011 - Depth Weighted

• 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

Shell Height (mm)

50 100 150 200

Meat Weight (g)

20 40 60 80 100 120 140 160 SARC 2010-MA General VIMS June 2011 SNE/LI - Depth Weighted

New York Bight

Shell Height (mm)

50 100 150 200

Grams

20 40 60 80 100 120 140 160 SARC 2010 MA General VIMS Sept. 2011 NYB - Depth Weighted

• 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.

• 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-Closed Areas

Shell Height (mm)

20 40 60 80 100 120 140 160 180 200

Frequency

200 400 600 800 1000 1200 1400 1600 Survey Dredge Commercial Dredge DMV

Shell Height (mm)

20 40 60 80 100 120 140 160 180 200

Frequency

1000 2000 3000 4000 5000 6000 7000 Survey Dredge Commercial Dredge GBCAII

• 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

Length Frequency-Open Areas

Shell Height (mm)

20 40 60 80 100 120 140 160 180 200

Frequency

1000 2000 3000 4000 Survey Dredge Commercial Dredge SNE/LI

Shell Height (mm)

50 100 150 200

Frequency

500 1000 1500 2000 2500 Survey Dredge Commercial Dredge NYB

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

Closed Area II- Recruited scallop abundance was widespread and density was relatively high. Very little recruitment in the area. Shell Height:Meat Weight was below expectation which was corroborated by Cfarm project. DelMarVa- Recruited scallop abundance was very low, although some signs of

• recruitment. May be difficult to get the scheduled ½ trip in 2012.

Southern New England/Long Island- Recruited scallop abundance was widespread and density was relatively high. Some recruitment observed esp. to West. New York Bight- Recruited scallop abundance was widespread and density was relatively low. Resource is very patchy. Some recruitment observed. Potential

• bservation of changes relating to the relative efficiency of the two dredges, esp.

in areas if high sand dollars (ongoing analysis). With respect to the open areas, we were able to obtain data to delineate the inshore extent of the scallop resource from Cape May to Martha’ Vineyard. In addition, we documented the above average SH:MW relationships for those areas.

2011 VIMS-Industry Cooperative Surveys

Summary

Acknowledgements

• The owners, captains and crews
• f the F/V Celtic, F/V Kathy Ann

and F/V Pursuit.

• Support from NMFS NEFSC:

Dvora Hart, Russ Brown, Vic Nordahl.

• NMFS Protected Species
• Funding through Sea Scallop

RSA program.

Photo courtesy of Shannah Jaburek