Water temperature and timing of capelin spawning determine seabird diets

Abstract

Abstract Davoren, G. K., Penton, P., Burke, C., and Montevecchi, W. A. 2012. Water temperature and timing of capelin spawning determine seabird diets. – ICES Journal of Marine Science, 69: . The capelin (Mallotus villosus) is the focal forage fish in many northern marine ecosystems. Its capacity to respond to changes in ocean climate is explored and the usefulness of seabird diets as indicators evaluated by integrating the timing of capelin spawning and temperature (0–150 m) during gonadal development (February–June) with colony-based measures of prey deliveries to chicks of common murres (Uria aalge) and northern gannets (Morus bassanus) on the east coast of Newfoundland during the years 1991–1993 and 2003–2010. Great variation was observed in the timing of spawning, with similar annual trends in different regions of coastal Newfoundland. Spawning was later in years of colder-than-average temperature, although the importance of other variables (e.g. fish size) could not be ruled out. The relationship between temperature during gonadal development and timing of spawning was weak at demersal spawning sites, suggesting that timing may be regulated by other factors (e.g. temperature at spawning sites). When spawning was early in warmer years relative to chick-rearing, common murres delivered a lower percentage of energy-rich gravid capelin to their chicks and northern gannets delivered a lower percentage of capelin. Integrating multiple data sources will be important to monitor marine ecosystem health as ocean climate changes.