Abstract
Seabird studies are useful for understanding the dynamic interactions between commercial fisheries, fish stocks and natural predators, since seabirds often are top predators sharing a resource base with the fisheries. Changes in the fish stocks may have effects on all life stages of fish predators. The response will partly be determined by state-dependent variables (e.g. age, sex, reproductive stage) and the response may differ between species. In addition, there may be indirect effects from changes in fish stocks, e.g. density-dependent prey-mediated effects on predator health. This project will use fish stocks (mainly sprat) and seabirds in the Baltic Sea as a case study to integrate detailed studies of state-dependant life history responses in predators and responses of ecologically similar predator species with changes in abundance and condition of prey. Indirect impacts will be addressed more specifically, by studying indicated links between thiaminase activity in pelagic fishes in the Baltic and waterfowl mortality and lowered seabird reproduction during the peak of the sprat stock. The results of this project will provide a scientific foundation for ecosystem-based management that will safeguard viable seabird populations. In addition, this will be valuable for a management of ecosystems striving for maintaining the ability to deliver desirable ecosystem goods and services.
Sweden