MEPS 445:25-35 (2012)  -  doi:10.3354/meps09465

Linking predator diet and prey availability: common murres and capelin in the Northwest Atlantic

Alejandro D. Buren1,*, Mariano Koen-Alonso1,2, William A. Montevecchi1

1Cognitive and Behavioural Ecology Programme, Departments of Biology and Psychology, Memorial University of Newfoundland, St. John’s, Newfoundland A1B 3X9, Canada
2Northwest Atlantic Fisheries Centre, Fisheries and Oceans Canada, PO Box 5667, St. John’s, Newfoundland A1C 5X1, Canada

ABSTRACT: We examined the predator–prey interaction between an apex seabird predator, the common murre Uria aalge, and capelin Mallotus villosus, the primary forage fish in the Northwest Atlantic. Sampling of parental deliveries to murre chicks was carried out during the breeding season on Funk Island, located off northeast Newfoundland, Canada. Concurrent vessel surveys were conducted throughout the murre’s diving and foraging range around the colony to characterize the prey field. Results indicated that in years when capelin was abundant in the size range consumed by murres (suitable capelin), murres delivered large and small fish in similar proportions, whereas they delivered more large fish when suitable capelin abundance was low. Considering the relative abundances of small and large suitable capelin, these observations suggest negative prey switching by the predator. Using foraging theory, we derived a model which estimates the probability of delivering a specific prey type (large or small capelin or other prey) to the chick based on prey availabilities. This quantitative model was capable of reproducing the ge