Research Document - 2001/003

Northern shrimp (Pandalus borealis) on the eastern Scotian Shelf - review of the 2000 fishery and outlook for 2001

By Koeller, P., Covey, M., King, M.

Abstract

The 2000 TAC of 5500 was caught without difficulty. Commercial catch rates continue to be excellent and the standardized CPUE index for 2000 is the highest of the series, although there has been a decrease in SFA 13 (Louisbourg Hole) catch rates. Trawl fishing effort in the newly (since 1998) exploited inshore area continued, but at a lower level than in 1999. Effort appears to be concentrating in smaller areas in recent years. The percent of the TAC caught in the non-ovigerous period (May-July) has decreased from about 70% prior to 1999, to 59% in 1999 and 52% in 2000. The June 2000 trawl survey showed a 13% decrease in the overal biomass, which came mainly from the decrease in SFA 13. A decrease in commercial CPUEs was also observed in this area. A re-interpretation of the population length-age composition indicates that "year class splitting", presumably due to depensatory growth caused by high densities, may have ocurred several times since the survey began in 1995. The strength of the 1997 and 1998 year classes appears to be about average, and fears that the apparent failure of the 1996 yc was due to recruitment overfishing may have been unfounded. Exploitation in terms of biomass has increased from 13% in 1999 to 17% in 2000. Females are being exploited at about 20% and males at between 10-20%. Catch composition indicates that very large, older shrimp accumulated in the population have been removed by fishing, however the spawning stock biomass remains high. Increasing temperatures, incursion of silver hake on the shrimp grounds, and decreasing capelin abundance may indicate that a regime shift to one less favourable to shrimp is under way. However, predator abundances remain low. Juvenile survey results suggest that these surveys could provide an estimate of year class strength 1-2 years in advance of the present June survey, but additional annual surveys are needed before this can be fully evaluated. Results also suggest that the inshore may be an important nursery area. An increasing number of "warning lights" for stock status indicators in the last two years suggests a slight decrease in the TAC for 2001.

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