Twice in the past 20 years, the capelin population in the Barents Sea north of Norway and Russia abruptly crashed and then took years to recover. It has again fallen sharply since 2001, in spite of restrictions on how many fish may be harvested there.
According to a new statistical analysis, the varying fortunes of capelin can be best understood and managed by accounting for not only fishing of that plankton-consuming species but also factors that affect cod and herring. Cod prey heavily on capelin, while herring eat some young capelin and compete with older ones for food.
"To manage this system, we have to understand the dynamic interaction of the various species as well as man's harvesting," says ecologist Nils Christian Stenseth of the University of Oslo.