Research Document - 2002/093

An assessment of American plaice in NAFO Subdivision 3Ps

By M. J. Morgan, W. B. Brodie, D. Power and S. J. Walsh

Abstract

The stock of American plaice in Subdivision 3Ps has been under moratorium since September 1993. Catches averaged just under 4000 t during the 1980's but rapidly declined after 1991. There has been no directed fishery since the moratorium was instituted. Catch has increased substantially since 1995, and in 2001 the catch was over 1,000 t. The catch to September 2002 was more than 900 t. The fishery has changed substantially compared to the premoratorium period with a larger inshore component, a substantial truncation in the length distribution and a much higher percentage of females in the catch. Since 1992, research vessel surveys indicate that the stock has been at a very low level. There has been a slight increase over the 1992-2002 time period in both biomass and abundance indices but average biomass over the last 3 years is only 20% and abundance 30% of the 1983-87 average. The female SSB index showed a large decline from the mid 1980's to the early 1990's and has shown a slight increase since 1997. The SSB index from 2000-2002 is 26% of the 1983-1987 average. Analyses of recruitment from survey data indicated that cohort strength declined from the 1979 to the 1995 year class. Since then cohort strength has generally increased. Although there is a broad range of observed recruitment at an SSB index below 10, recruitment level does increase with SSB and the best observed recruitment was above and SSB index of 20. The current SSB index is about 9. Catch/biomass ratio declined rapidly after 1990 as catches decreased, and reached a minimum in 1995. Catch to survey biomass ratios indicate that exploitation rate has been increasing since the mid 1990's. In the next few years the weak 1994-1997 year classes will be moving into the age range of the biomass subject to the bycatch fishery. This will likely result in a decrease in exploitable biomass. At current levels of catch this should result in a further increase in fishing mortality. More recent year classes appear stronger but these will not contribute to the exploitable biomass or SSB for several more years.

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