Changes in the population of American plaice (Hippoglossoides platessoides) off Labrador and northeastern Newfoundland: A collapsing stock with low exploitation

Changes in the population dynamics of American plaice off southern Labrador and eastern Newfoundland (NAFO Subarea 2 and Division 3K) for the period 1977-1994 were investigated. Since the mid 1980s the population has declined dramatically and by the 1990s the stock had essentially collapsed. A higher proportion of what remained of the stock was found in deeper and warmer water than had previously been observed, coincident with a period of unusually cold ocean conditions, During the period of the greatest reductions in population size, the proportion of older, spawning-age fish declined much more rapidly than the younger ages and this decline was accompanied by a slight decrease in mean size at age. Also associated with these observations were declining trends in both size and age at maturity. Although exploitation has always been low, the fishery for American plaice in NAFO Subarea 2 and Division 3K has been regulated since the early 1970s. For the period investigated the average annual commercial exploitation rate was less than 2% with negligible bycatch in other fisheries. We conclude, therefore, that the collapse of this stock was not a result of fishing mortality. The causal mechanism for the decline remains unclear although unusual environmental conditions during the period continue to be investigated in relation to the observed changes in this population. (C) 1997 Elsevier Science B.V.