Interactions between northern shrimp, Pandalus borealis (Pandalidae), and its key predators within the eastern Newfoundland and Labrador marine ecosystem

An examination of population trends for northern shrimp (Pandalus borealis) and its key predators off eastern Newfoundland and Labrador provided the basis for investigating predator-prey relationships within an ecosystem that experienced major changes in species composition during the 1980s and 1990s. Populations of several demersal fish species, known to feed on northern shrimp, declined to historically low levels by the early 1990s and remained depressed thereafter. Some declines were precipitous from the late 1980s to early 1990s, coincident with an increase in shrimp. Populations of other important predator species increased throughout the 1990s along with shrimp. Lacking representative estimates of shrimp consumption, the net effect on predation mortality was unquantifiable and it was not possible to demonstrate with certainty that the major increase in shrimp biomass that occurred throughout the 1990s resulted from a concomitant reduction in predation mortality. Factors (and their interactions) relevant to the dynamics of shrimp populations include the effects of ocean climate, predation, competition, as well as commercial harvesting.