Research Document - 2002/050
An Assessment of Newfoundland and Labrador Snow Crab in 2001
By E. G. Dawe, H. J. Drew, P. J. Veitch, R. Turpin, P. G. O'Keefe, and P. C. Beck
Abstract
Data from the commercial fishery since 1973, as well as 1995-2001 survey data were used to infer resource status of Newfoundland and Labrador snow crab (Chionoecetes opilio) for the 2002 fishery. Annual trends in landings, effort and catch per unit effort (CPUE) throughout NAFO Div. 2J3KLNO were reviewed and updated for 2001. CPUE from offshore fleets increased in the late 1980's and have remained generally high, although they declined after 1998 in Div. 2J3K. This reflects recent high commercial biomass relative to that of the mid 1980's overall that is decreasing in the north. Data utilized from the Div. 2J3KLNO 2001 fall multispecies bottom trawl surveys during 1995-2001 included catch rate, size (carapace width, CW), sex, maturity, egg development and molt status (shell condition and chela allometry). These surveys are conducted near the end of the fishing season and so are considered to provide an index of post-fishery biomass. Legal-sized and prerecruit males were broadly distributed throughout much of the survey area but were absent from Div. 2GH and 3M, some inshore areas, and across much of the shallow southern Grand Bank. These surveys indicate that the exploitable biomass decreased between 1999 and 2000 and has remained stable since then. The exploitable biomass available to the Div. 2J3KLNO fishery in 2002 is expected to be not substantially different from that of the previous two years. The biomass of immediate prerecruits decreased during 1997-2000, increased in 2001 and has remained unchanged for 2002. However there is high uncertainty associated with these trends in exploitable biomass and prerecruits because of variable catchability of crabs by substrate type. The ratio of catch to the projected exploitable biomass index has increased steadily from 1997-2001, implying an increase in exploitation rate. Annual trends in exploitable biomass indices agree with trends in fishery performance in northern areas, especially in Div. 2J, whereas these indices for Div. 3L are in opposition. However there is high uncertainty about both indices because the fishery data are not standardized for effects of annual changes in fishing practices, and the survey series does not account for strong effects of crab size and substrate type on catchability by the survey trawl. The apparent increase in exploitation rate has had minimal impact on reproductive potential. Abundance of mature females has declined since 1995 throughout Div. 2J3KLNO but sex ratios of adults continue to favor males and there is no evidence of any decrease in mating success of females. Resource status and prospects for Subdiv. 3Ps or Div. 4R are uncertain because of a lack of fishery-independent data. Offshore CPUE in Subdiv. 3Ps increased steadily to 1999 and has since declined, but remains above the low level of the 1980's. Div. 4R CPUE has remained stable over the past 4 years at a lower level than in other divisions.
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