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Biological characteristics, population dynamics, and current status of redfish, Sebastes fasciatus Storer, in the Gulf of Maine-Georges Bank region
  • Published Date:
    2002
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Biological characteristics, population dynamics, and current status of redfish, Sebastes fasciatus Storer, in the Gulf of Maine-Georges Bank region
Details:
  • Corporate Authors:
    Northeast Fisheries Science Center (U.S.)
  • Series:
    Northeast Fisheries Science Center reference document ; 02-05
  • Document Type:
  • Description:
    The status of the Gulf of Maine/Georges Bank redfish (Sebastes fasciatus) stock through 2000 is reviewed, and the current status of the stock is compared on a relative basis to revised estimates MSY-based reference points. The 2001 assessment is based on several sources of information including: the age composition of USA commercial landings, Northeast Fisheries Science Center (NEFSC) spring and autumn research vessel survey data, and standardized USA commercial fishing effort data. This assessment updates the analyses presented in the 1993 assessment of the Gulf of Maine/Georges Bank redfish stock as well as that prepared in 2000 by the Northern Demersal Working Group. Information on the size and age structure of the redfish stock is presented including: age composition of the commercial landings (1969-1985), length composition of inshore and offshore components of the stock based on NEFSC spring (1968-2000) and autumn (1963-2000) research vessel surveys, and age composition of the stock based on NEFSC spring and autumn research vessel surveys (1975-2000). Several aspects of the biology of the redfish stock are also presented including patterns in diurnal catchability, length-weight relationships, analyses of maturity at length, and inshore/offshore biomass comparisons. The assessment of current status is based on several analyses including trends in catch/survey biomass exploitation ratios; a yield and biomass per recruit analysis; an age-structured dynamics model which incorporates information on the age composition of the landings, size and age composition of the population, and trends in relative abundance derived from commercial CPUE and research vessel survey biomass indices; and an age-aggregated biomass dynamics model. Surplus production estimates were derived from the age-structured production model, and information on current status of biomass and fishing mortality relative to MSY-based reference points is also provided by the biomass dynamics model. The fishery on this stock developed during the 1930s. Landings rose rapidly from less than 100 mt in the early 1930s to over 20,000 mt in 1939, peaking at 56,000 mt in 1942, then declined throughout the 1940s and 1950s. Redfish have been harvested primarily by domestic vessels, although distant water fleets took considerable quantities for a brief period during the early 1970s. The distant water fleet effort, combined with increased domestic fishing effort, resulted in a brief increase in total catch to about 20,000 mt during the early 1970s. Landings declined throughout the 1980s and have averaged less than 500 mt per year during the 1990s. Exploitation ratios (catch/survey biomass) suggest that fishing mortality has been very low since the mid-1980s compared to previous periods. Estimates of fishing mortality derived from the age-structured dynamics model and the age-aggregated biomass model are similar, both indicating that current fishing mortality is low relative to past decades and with respect to Fmsy (<5%). Stock biomass has increased since the mid-1990s, and is presently estimated to be about 33% of Bmsy due, in large part, to recruitment of one or more strong year classes from the early 1990s.