Research Document 2020/019

Assessment of the American Plaice (Hippoglossoides platessoides) stock in NAFO Subdivision 3Ps in 2019

By Morgan, M.J., Rogers, R., Ings, D. and Wheeland, L.

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 has been less than 200 t in all but one year (2017) since 2011. From the mid-1980s to 1990 there was a large decline in both biomass and abundance indices. Indices of stock size were lowest in the early 1990s. There was a general increase over the 1992-2011 period for both biomass and abundance indices with both indices varying essentially without trend since. The average abundance over the last three years is only 39% and biomass only 20% of the average from 1983-1985. Ageing is not available for this stock for the last several years. Length frequencies from the survey from 2009-2013 were examined for indications of recruitment in recent years. A year class can be followed from 2008 and another from 2013. Despite the appearance of these year classes, from 2008-2019 there are few fish greater than 30 cm, indicating that these year classes have not survived to older ages. The surplus production model used to assess the status of the stock estimates that an MSY of 2,879 t can be taken from a biomass of 70,290 t at a fishing mortality of 0.041. 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. B_lim for American Plaice in NAFO Subdivision 3Ps is 40% B_MSY. Biomass of the stock in 2019 is estimated to be 65% below B_lim and therefore the stock is in the Critical Zone. The probability of being below Blim is high (0.98). Current median fishing mortality is estimated to be 24% of F_lim and the probability of being above F_lim (F_MSY) is low (0.03). The stock has shown little or no growth since 2008. Projections of stock size were conducted to the beginning of 2023 under conditions of zero catch, current F, current F plus 15%, and current F minus 15%. Although the stock is projected to grow under all scenarios, at the end of the projection period there is a high probability of being below Blim, even under zero catch. There is no catch which gives a high (95%) probability of stock growth. To increase the probability of stock recovery, there should be no directed fishing and bycatch should be kept to the lowest possible level.

Research Document 2020/019 (PDF, 1,453 KB)

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