Research Document - 1999/172

The Scotian Shelf shrimp (Pandalus borealis) fishery in 1999.)

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

Abstract

Survey biomass continued to increase in 1999 and the overal index was the highest of the five year DFO-industry series. The 1999 increase is mainly due to increases in SFA 13 and 15, which have not been heavily fished recently, together with sustained high abundance in SFA 14 and the inshore zone. The standardised commercial CPUE index also increased in 1999 and continues to closely parallel the survey series. During 1999 fishers continued to take advantage of the good catch rates and availability of large shrimp in the inshore zone. The proportion of the total catch taken in this area doubled from 20% in 1998 to 40% in 1999 and the exploitation rate increased from 8 to over 22%. Standard survey population estimates at length and age and experimental recruitment survey results indicate that the 1996 year class is very weak with commercial sampling and an experimental recruitment survey confirming the scarcity of 3 year old shrimp. Egg disease was widely reported in 1996, however observations on disease incidence were not initiated until after hatching and the data cannot be used to confirm that egg disease caused this apparent year class failure. The 1995 year class, which appeared to be about average in 1998, is now the largest of the series and the abundance of males indicates a high spawning stock and good catch rates of large shrimp in 2000. Size-specific exploitation rates remain relatively low, at <10% for males and <20% for females. Temperatures were relatively warmer in 1999 than in 1998, however, temperatures have been variable over the last few years and there is no apparent trend in the data. Although predator (finfish) biomass is at an all time low there are some, albeit inconsistent, indications of improved cod recruitment which may impact on shrimp mortality in the future. A cautious increase in the overall TAC is again recommended for 2000 to take advantage of the strong 1995 year class, but a reduction may be indicated in 2001 when the 1996 yc recruits to the fishery and proves to be weak. The 1998-99 Mahone Bay and Chedebucto Bay trap fisheries continued with catch rates similar to the previous year, but with an earlier spring decline in the later. Catch rates in Chedebucto Bay at the beginning of the 1999-2000 season were similar to the previous year. Current and retrospective "traffic light" analyses of the Scotian Shelf shrimp stock and hypothetical harvest rules were used to illustrate how assessment "scores" could be linked to TACs in a precautionary management framework.

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