CHANGES IN THE POPULATION OF AMERICAN PLAICE (HIPPOGLOSSOIDES-PLATESSOIDES) OFF LABRADOR AND NORTHEASTERN NEWFOUNDLAND - A COLLAPSING STOCKWITH LOW EXPLOITATION

Changes in the population dynamics of American plaice off southern Lab rador and eastern Newfoundland (NAFO Subarea 2 and Division 3K) for th e period 1977-1994 were investigated. Since the mid 1980s the populati on has declined dramatically and by the 1990s the stock had essentiall y collapsed. A higher proportion of what remained of the stock was fou nd in deeper and warmer water than had previously been observed, coinc ident with a period of unusually cold ocean conditions, During the per iod of the greatest reductions in population size, the proportion of o lder, spawning-age fish declined much more rapidly than the younger ag es 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 bee n low, the fishery for American plaice in NAFO Subarea 2 and Division 3K has been regulated since the early 1970s. For the period investigat ed the average annual commercial exploitation rate was less than 2% wi th 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 env ironmental conditions during the period continue to be investigated in relation to the observed changes in this population. (C) 1997 Elsevie r Science B.V.