Research Document - 1999/180
Evaluation of the 1998 4WX herring acoustic surveys.
By G.D. Melvin, T. Scheidl, F.J. Fife, M.J. Power, S. Boates, K. Clark, and R.L. Stephenson
Abstract
Automated acoustic logging systems installed on commercial herring purse seine boats were used to document the distribution and abundance of herring in NAFO Division 4WX during the 1998 fishing season. As in previous years, data were collected during both fishing operations and structured (science-directed mapping/acoustic) surveys. The number of structured surveys in southwest Nova Scotia decreased from five in 1997 to three in 1998 and most biomass estimates were instead computed from fishing operations. The number of automated systems increased from two to six. Total biomass estimates for a spawning component was determined by summing the surveys and/or fishing estimates of greater than ten days intervals. Biomass estimates for German Bank, Scots Bay, Trinity Ledge and Spectacle Buoy were 440,700t, 72,500t, 6,800t and 1,300t respectively. Based on this approach the spawning stock biomass of 4WX herring stock complex was estimated to be 521,300t, down slightly from 568,500t in 1997.
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