Abstract
Since autumn 2006 the American ctenophore Mnemiopsis leidyi occurs in Skagerrak, Kattegatt and the Baltic. It reproduces rapidly and feeds efficiently on plankton, fish larvae and eggs. A permanent establishment may therefore be detrimental and in the worst case scenario lead to regime shifts from fish to jellyfish dominance. In the Black Sea, fisheries collapses coincided with the Mnemiopsis invasion. Ecosystem effects depend on complex food web and environmental interactions. It is not possible to forecast effects of Mnemiopsis in Swedish waters based on lessons from other waters. We plan quantitative studies of how Mnemiopsis catches prey. We will use sophisticated video methods and mechanistic modeling, in collaboration with world leading American researches. By combining models with experimentally determined clearance rates, field abundances and stomach analyses we will estimate predation pressure on zooplankton and fish larvae. Reproductive potential and survival will be examined in experiments as a function of temperature and salinity. Results will be combined with field data of temperature, salinity and predators to estimate Menmiopsis´ ecological boundaries in the Baltic. Ctenophores do not depend on light for prey detection and may therefore outcompete fish when light environment changes, for ex. due to eutrophication. Effects on fish by contemporary changes in optical and temperature environment will be modeled in collaboration with Norwegian scientists.
Sweden