ABUNDANCE, DYNAMICS AND MORTALITY RATES OF THE DELAWARE BAY STOCK OF BLUE CRABS, CALLINECTES SAPIDUS

Abstract

Abstract The Delaware Bay stock of blue crabs supports a bistate fishery in New Jersey and Delaware, with annual landings climbing through the 1980s and 1990s to almost 11 × 106 pounds (4,390 metric tons) in 1995 and then declining to a recent average of 7 × 106 pounds (2,796 metric tons) over the last 5 y. In Delaware, this fishery ranks as number one in value. Landings declines in 1996 spurred efforts to conduct a stock assessment, which is now updated annually. This assessment was based on: (1) a biomass-based minimum recruitment threshold from a Ricker stock-recruitment model fit to indices of relative abundance from a research trawl survey and (2) a catch-survey model incorporating observation and process error that produced annual estimates of absolute abundance, biomass, and fishing mortality rates from 1979 through 2002. Adult blue crab abundance estimates showed a positive trend over the period, ranging from 20 × 106 in 1979 up to 146 × 106 in 1993, with recent estimates between 70 × 106 and 97 ×...