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 <120 mm migrated with smaller, shorter-distance (0-100 m) migrators (copepods). These patterns influenced the diurnal feeding patterns of top predators. Vessel-based measures of observed seabird distributional patterns and trawl-estimated capelin availability and colony-based measures of seabird diets J. Northw. Atl. Fish. Sci., 39: 35-48. doi:10.2960/J.v39.m595 http://journal.nafo.int J. Northw. Atl. Fish. Sci., Vol. 39, 2008 36 revealed that seabirds are selective in their pursuit of forage prey and that they expand their foraging ranges considerably when capelin were less available in certain years. Furthermore, changes in the dietary composition of common murre (Uria aalge) can be linked to changes in the availability of 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.

Crepuscular foraging by a pursuit-diving seabird: tactics of common murres in response to the diel vertical migration of capelin

“…We assess these diurnal associations by comparing hydroacoustic survey data of capelin and bird-borne device data from common murres collected in the waters surrounding the seabird breeding colony on Funk Island, Newfoundland, in the northwest Atlantic Ocean. The broad-scale vertical movements of capelin (migrate < 300 m; Davoren et al 2007) and diving capabilities of murres (dive <177 m; present study) make these species excellent candidates to evaluate these associations.…”

A review of the use of seabirds as indicators in fisheries and ecosystem management

“…In one of the first examples of an Ecologically Sustainable Development management program the breeding numbers of two gull species constitute one of 13 important ecological performance indicators of ecosystem function in the North Sea (Kabuta and Laane, 2003). In the Northwest Atlantic the diet and foraging effort of two seabird species have been incorporated into a similar multi-disciplinary management program (Davoren et al, 2007). An integrative multi-species research program exists in the South Atlantic Ocean, where the diet and breeding success of three seabird species are incorporated into an index of inter-annual changes in krill Euphausia superba abundance, being a measure of the productivity in this ecosystem (Croxall, 2006).…”

Lack of genetic divergence in capelin (Mallotusvillosus) spawning at beach versus subtidal habitats in coastal embayments of Newfoundland

“…Throughout their circumpolar distribution, beach and demersal sites do not typically occur in close proximity. Recently, however, persistent demersal spawning sites have been discovered adjacent to spawning beaches (subtidal) at two coastal Newfoundland locations (Nakashima and Wheeler 2002;Davoren et al 2008).…”