| Summary: | Background: Common guillemots are integral elements of the Baltic Sea marine ecosystem. They possess life-history characteristics such as relatively long lifespan, quite low fecundity resulting in only one egg per breeding season – characteristics that make them particularly vulnerable to even small changes in the environment. Higher weight of their single chick, gained during the breeding season, ensures higher survival rates for Guillemot fledglings. Hence, during the breeding season not only quantity but also quality of prey within the foraging area are central for their reproduction success. Objectives: This study applies the match-mismatch hypothesis on a predator-prey relationship by investigating common guillemot chicks’ fledgling weight on Stora Karlsö in relation to their key prey, sprat and herring. Maturity in sprat and herring were used as an indicator for fitness and spawning abundance of food quality for parental guillemot for raising chicks’. Data: The study used data of chicks’ weights when leaving their nests from common guillemots (40,936 chicks) collected between 2007 and 2017 from the Swedish Baltic Sea Bird Project. Data of sprat and herring gonadal maturity was obtained from the PLANFISH project and inspections of catches from the commercial and industrial fisheries. Method: Common guillemot chick fledgling weights between years were analysed by Analysis of Variance (ANOVA). Maturity in sprat and herring were used as a proxy to estimate spawning state and predict the peak day of highest abundance of potential spawners. A Generalized Additive Model (GAM) was used to predict the peak day of highest abundance of potential spawners. For estimating match-mismatch lags, a cross-correlation function analysis (CCF) was conducted to analyse chick fledgling weight in relation to sprat and herring’s maturity states (fitness). Results: The study showed that common guillemot chicks have decreased in weight annually between 2002 and 2017. The results further show that it is obviously more advantageous ...
|
|---|