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Correcting for effective area fished in fishery-dependent depletion estimates of abundance and capture efficiency
Walter, JF Hoenig, JM Gedamke, T
Walter, JF
Hoenig, JM
Gedamke, T
Abstract
Depletion methods are widely used to estimate capture efficiency and abundance. However, they are highly dependent on the depletion area assumed. In open-ocean depletion studies, it is difficult to determine the true area of depletion. Satellite vessel monitoring systems (VMS) offer the potential to determine the area effectively fished. Observer-collected catch-and-effort data from the 1999 Atlantic sea scallop fishery in Georges Bank Closed Area II were used to obtain spatially-explicit DeLury depletion estimates of dredge efficiency and abundance, with corrections for fished area made using VMS data. Non-area-corrected efficiency estimates often had theoretically impossible values, indicating that the naively assumed fished area was likely too big. Fine-scale spatial analyses on individual depletion cells confirmed this result. Corrected-area efficiency estimates exhibited reduced variability and more plausible efficiencies, with 70% of 289 individual depletion estimates failing between 20% and 55%, with a mean of 46%. Abundance estimates from individual depletion studies matched maps of abundance from a preseason survey. Results indicated a total abundance of similar to 17 million pounds of scallop meat weight in the fished area, of which 6 million pounds were landed, providing an overall exploitation rate of 35%.
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2007-01-01
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fsm147.pdf
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Fisheries Science Peer-Reviewed Articles, Scallop Placopecten-Magellanicus; Georges Bank; Sea Scallops; Movement
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Virginia Institute of Marine Science
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https://doi.org/10.1093/icesjms/fsm147