Citation: Erikstad, K. E., T. K. Reiertsen, R. T. Barrett, F. Vikebø, and H. Sandvik (2012) Temporal variation in fish abundance affects seabird populations: cod–guillemot interactions in the Barents Sea. – Talk given by H. Sandvik at the 36th Annual Larval Fish Conference in Osøyro.
Abstract: Small pelagic fish and young age classes of larger predatory fish
constitute the most important prey of seabirds. Fish abundance has long been hypothesized to
play a major role in regulating seabird populations. Climatic fluctuations, commercial
fisheries and interactions between fish species and the environment may cause pronounced
spatial and temporal variation in fish abundance and affect seabird populations in many areas.
We have analysed the temporal variation in the population of common guillemots
(Uria aalge) in a colony in NE Norway (Hornoya) between 1980 and 2010 in relation
to the variation in abundance (acoustic and trawl surveys) of important fish prey species
in the Barents Sea. The fish species considered were all age classes of capelin
(Mallotus villosus), 0- and I-group herring (Clupea harengus) and 0- and
I-group cod (Gadus morhua). The annual variation in guillemot population growth rate
could best be explained by the variation in abundance of 0-group cod and the 0-group cod six
years earlier (equalling the age of maturation of guillemots). The very strong positive
relationship between the youngest age class of cod and the variation in the common guillemot
population growth rate undermines the earlier belief that the capelin stock has a major
effect on the population dynamics of common guillemots. A numerical ocean model was used
to identify mechanisms affecting spatio-temporal prey availability of 0-group cod around
the colony during the breeding season.
Related publications: This study has now been published in Marine Ecology Progress Series.