Fish Ecology

Baltic coastal populations of predatory fish, mainly perch and pike, has been greatly reduced in recent decades. Underlying causes can be altered food webs, competition and disrupted reproduction environments.

We aim to build knowledge on coastal fish populations in terms of ecology, interactions between fish and other components of the food web and migration of fish between the Baltic Sea and freshwater environments such as streams and rivers.

Our research

The group is a part of Linnaeus University Centre for Ecology and Evolution in Microbial model Systems

Our research has applied aspects that contribute to the knowledge about how restoration of reproduction environments can recreate a balanced ecosystem. We use methods as electronic tagging of fish, genetic methods (microsatellites), otolith chemistry (balance stones) and stable isotopes.

We have, through a large-scale labelling of mature fish, showed that e.g. pike forage in the sea during most of the year, but migrate up the streams and rivers to spawn in the spring. The fishes have a "homing" behavior, as they return year after year to the same spawning area. This can be shown by the accumulation of substances in the otoliths; the fish take up an unique pattern of substances depending on what kind of water they spawn in. "Homing" behavior leads to the creation of barriers between different populations or sub-populations, e.g. of pike, where each population has its own specific spawning area. From spawning grounds like creeks and streams, the fry migrate into the sea where they grow up. Then, when they become adults, they return to their home waters for spawning. The results indicate that freshwater environments is of great value as reproduction sites for fishes originating from freshwater. This can be used to restore or create good spawning grounds for fish in the Baltic Sea catchment area, thereby strengthen the populations.

The division in populations of coastal stocks, of e.g. pike and perch also has other implications. Individuals of these populations may be (evolutionarily) adapted for their particular environment. This adaptation may apply to behavior (spawning season, the fry size at migration) or morphological changes (growth, size). We conduct so-called "Common-garden" experiments (crossing female-male from different populations that gives fry) in the laboratory in order to identify the population's unique characteristics.