Skinny Predators Indicate Troubling Changes In Baltic Sea Food Web·
The prime predators of the Baltic Sea at the top of the food web are losing weight, according to a new study that links the deteriorating health of gray seals and cod with changes in bottom-living crustaceans, isopods and amphipods.
“It is important that you understand how the food web works when managing a fishery. It is not enough to manage how the fish and fisheries are changing. The availability and quality of food is at least as important,” says Lena Bergström, researcher at the Department of Aquatic Resources at the Swedish Agricultural University.
In a collaboration between several universities, the authors of the study examined how the health and abundance of certain species has changed over two decades in the Bothnian Sea and the Baltic Proper. They investigated seal, cod, herring, sprat, isopods, amphipods and zooplankton, species that all occur at different levels in the Baltic Sea food web. The system is complex and several species can be both predators and prey. For example, herring eats zooplankton and some bottom fauna while the herring itself is eaten by cod and seal.
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