An ecosystem-based research program for capelin (Mallotus villosus) in the northwest Atlantic: overview and results

Abstract

The Northwest Atlantic has been undergoing extensive ecosystem shifts involving oceanographic change and over-fishing. Capelin (Mallotus villosus), the focal forage fish species in this system, is a primary prey for most large predators, including cod, seals, whales and seabirds. Recently, the biology and behaviour of capelin has changed dramatically, although the basis for these changes is not well understood. Through a collaborative, multi-disciplinary research program among university, government and commercial fishers, we investigated mechanisms underlying these changes. In this manuscript we present an integrated overview of this initiative and synthesize key results from research carried out within the program. Our meso-scale study area encompassed the Funk Island Seabird Ecological Reserve, situated 60 km northeast of the Newfoundland coast. We identified 11 off-beach demersal spawning sites of capelin, which were primarily associated with small gravel in bathymetric depressions where temperatures were >2°C. Through comparisons of beach and demersal spawning, we described two distinct developmental strategies of eggs: high mortality and rapid development for beach sites versus low mortality and slow development for demersal sites. Emergence strategies of larvae at demersal sites also differed from beach sites elsewhere in Newfoundland. Integrating results from vessel-based and moored hydroacoustics (Acoustic Doppler Current Profilers) and biological sampling suggested that the diel vertical migratory patterns of capelin and its zooplankton prey are related. Capelin >120 mm total length migrated with larger, longer-distance (0–300 m) crustacean migrators (amphipods, euphausiids), whereas capelin 100 mm, suggesting that the diet of common murre, and perhaps of other seabirds, has the potential for becoming a quantitative indicator of capelin status. Overall, this type of research framework will be important for moving toward ecosystem-based management approaches.