The ecology of focal forage fish species 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. I recently discovered capelin spawning in deep water (demersal) in coastal Newfoundland, where this species is primarily thought to spawn on beaches. Large aggregations of capelin form at these spawning sites, causing predators to concentrate. This results in areas where high abundances of organisms gather, often referred to as 'biological hotspots'. My research focuses on the interaction of capelin with their physical environment and other species within these hotspots. Specifically, I examine whether capelin select between beach and demersal spawning habitat on the basis of current environmental conditions or whether capelin have evolved into different populations of obligate beach and demersal spawners. Additionally, I examine how foraging within hotspots influences the biology of capelin predators. To do this, I employ a novel assemblage of sophisticated marine electronic equipment aboard ships. I combine these measures with laboratory-based tank experiments, genetic analyses, otolith microstructure and stable isotope techniques, along with predator foraging strategies. My research involves collaborative efforts between university scientists and commercial fishers, which has and will continue to make major advancements in our understanding of fish ecology and food web dynamics. Ultimately, this research will increase the accuracy of capelin stock assessment indices and promote novel, incisive fisheries management approaches to avoid ecological and socioeconomic catastrophes that have occurred in our coastal waters and communities around the globe.