Research Document - 2014/098

An assessment of the American plaice (Hippoglossoides platessoides) stock in NAFO Subdivision 3Ps

By M. J. Morgan, K. S. Dwyer, B. P. Healey and R. M. Rideout

Abstract

There has been a moratorium on direct fishing of American plaice since September of 1993. Since then, there has been only by-catch of American plaice in other fisheries. Catch increased substantially after 1995, and was over 1,000 t in each year from 2001 to 2003. However, catch has been declining since then and was 300 t, 151 t and 103 t in 2011, 2012 and 2013, respectively. Biomass and abundance indices from 1983-2013 from research vessel surveys showed a large decline from the mid 1980s to 1990. There was a general increase over 1992-2011 for both biomass and abundance indices but both declined from 2011 to 2013. The average abundance over the last 3 years is only 44 % and biomass only 21 % of the average from 1983-1985. Stock size estimated from the surplus production model decreased fairly steadily from the late 1960s to a low in 1994 of less than 10 % of B_msy. Biomass increased slowly from 1994 to 2008 but has not increased since. Biomass in 2013 is estimated to be only 40 % of B_lim and therefore the stock is in the Critical Zone. Taking uncertainty into account, the probability of being below B_lim is high (0.97). Fishing mortality reached a peak in 1991 after which it declined for several years. Fishing mortality increased again to above F_msy in the late 1990s when landings started to increase. It has declined since 2010 and current median fishing mortality is estimated to be 20 % of F_lim. The probability of being above F_lim is low (0.05). If catch of American plaice were to be reduced to zero, the stock would show some increase over the next 3 years. By the end of 2016 the median of the ratio of biomass to B_msy is projected to be 0.22 (55 % of B_lim) but the probability of being below B_lim remains high (0.85). Projections determined that annual catches of 1000 t or more will likely result in stock decline. Any catch will result in even slower stock growth and an increased probability of being below B_lim.

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