Comparing capelin abundance estimates from predator diet data and an acoustic survey

Abstract

In Newfoundland and Labrador marine food webs, capelin (Mallotus villosus) is a critical energetic link between zooplankton and larger vertebrates, making an accurate assessment of capelin population dynamics integral to effective regional fisheries management. In 1990–1991, the capelin population off the east coast of Newfoundland collapsed, with limited recovery since. Shifts in capelin biology and uncertainties associated with capelin survey data since their collapse have limited understanding of the causes of the capelin collapse and subsequent lack of recovery. We sought to gain a better understanding of capelin population dynamics by modifying a recently developed integrated prey dynamics model to account for temperature-and ontogenetic-induced diet shifts. The best-performing model included an ontogenetic, but not temperature-induced, diet shift to account for changes in predator selectivity. Abundance estimates from our model were not correlated with current assessment estimates. Different estimated trends between predators indicated potential spatial and temporal shifts in predator-prey dynamics. This model helps improve understanding of capelin population dynamics by compensating for limitations associated with individual data sources.