The ecology of focal forage fish and its impact on marine predators

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Capelin, a small minnow-like fish, is the focal forage fish species that preys on many invertebrates and is in turn preyed on by most large predators, including cod, seals, whales and birds in the Northwest Atlantic. Capelin provide essential linkages for energy transfer among trophic levels and, thus, are often thought to mediate ecosystem-level changes. In previous NSERC-funded expeditions, we discovered that the timing of capelin spawning is highly variable. This is critical as many top predators rely on large inshore aggregations of pre-spawning and spawning capelin as an abundant and predictable food source. Our research aims to investigate factors influencing the timing of capelin spawning by examining whether capelin of varying age and experience spawn at different times due to differences in maturation rates. Additionally, we compare the time and energy expended by foraging top predators when inshore aggregations of capelin are present and absent. To do this, we employ a novel assemblage of sophisticated marine remote sensing equipment, both ship-based and moored, combined with animal-borne miniature telemetry devices to examine individual-level foraging behaviour of predators. Our research involves collaborative efforts between university researchers and commercial fishers, which has and will continue to make major advancements in our understanding of capelin ecology and how changes influence top predators. Ultimately, this research will increase the accuracy of capelin stock assessment indices and promote novel, ecosystem-based management approaches to avoid ecological and socioeconomic catastrophes that have occurred in coastal waters and communities around the globe.