The collapse and continued low productivity of a keystone forage fish species

摘要

Capelin are a focal forage species in the Northwest Atlantic ecosystem as they act as an energy conduit from lower to higher trophic levels. Fisheries and Oceans Canada determined that the Newfoundland capelin stock (Northwest Atlantic Fisheries Organization Divisions 2J3KL) suffered an order of magnitude decline in biomass in 1990-1991. This collapse was concomitant with drastic changes observed in the ecosystem during the late 1980s and early 1990s. While the results of more than a dozen studies have supported the capelin stock collapse hypothesis, an alternative non-collapse hypothesis proposed that rather than collapsing in 1990-1991, the capelin stock either (1) changed its migratory patterns while the timing of the spring capelin acoustic survey remained constant, leading to a spatio-temporal mismatch between the spring acoustic survey and the stock, or (2) became less migratory and remained inshore year-round, therefore being largely underestimated by the offshore spring and fall acoustic surveys. The collapse and non-collapse hypotheses were tested using multiple independent data sets, which included both fishery-dependent (inshore commercial catch) and fishery-independent (spring and fall acoustic and fall bottom-trawl surveys, capelin larval indices, aerial surveys, predator diet and behavior) data, and diverse statistical methods. The weight of evidence approach led us to reject the non-collapse hypothesis and conclude that the Newfoundland capelin stock did collapse in 1990-1991 with minimal recovery over the subsequent 3 decades.