Results of Commercial Sea Scallop Survey in the Hudson Canyon South Closed Area
DuPaul, William D. Rudders, David B. Rago, Paul J.
DuPaul, William D.
Rudders, David B.
Rago, Paul J.
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Abstract
This report presents the results of the commercial survey of the Hudson Canyon Closed Area. The survey was conducted aboard the FN Alice Amanda from June 8-15, 2000. A systematic grid design was utilized with survey stations located approximately 5 nm apart (Figure l ). Survey stations were located both inside and outside the boundaries of the closed area. Additional stations were added along the western, northern ru1d southern boundaries in an attempt to resolve the boundary effects on sea scallop abundance and size distribution. Survey tows were l O minutes in duration at a speed of 4.5-5.0 kts. The sampling gear consisted of two standard 15 ft. New Bedford style sea scallop dredges with 8 inch twine tops. ring bags knit with 3.5'' (88.9 mm) rings, and no tickler or rock chains. An inclinometer was attached to the frame of the starboard dredge to measure dredge angle and bottom contact time. The results of the initial data analysis are shovm in Figures 2-8. Catch data are shown in Figures 2-4 with scallop catches separated into two categories of shell height: less than 90 mm (Figure 2) and greater than or equal to 90 mm shell height (Figure 3). A total scallop catch at each station is shown in Figure 4. Differences in sea scallop abundance and size structure were examined with respect to samples taken inside or outside of the closed area (Figure 5), strata calculated by dividing the closed area into equal North and South portions along the 39° 01.566' latitude (Figure 6), and by depth regimes within the closed area (Figure 7). Catch data stratified by two factors: 1 ). North and South 2). inside and outside the closed area are shown in Table l. The initial biomass estimate is shown in Table 2. The following assumptions were used in calculating biomass: l. Stratification of the closed area into two roughly equal portions. 2. Utilizing a systematic grid design, number of stations was proportional to area of strata. 3. Tows that fell on closed area boundary were included in the calculation. 4. All scallops harvested were included 5. The coefficients of the shell height-meat weight relationship a=-12.1628 b=3.2539. 6. A nominal tow length of 1 nm. Each tow covered 0.00494 nm2 • 7. A dredge efficiency of 40% 8. Harvest represents a removal of 25% of the standing stock
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2000-09-06
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Marine Resource Reports
Research and Technical Reports, Scallops, Fisheries, Monitoring, Virginia