Male gray seals specialize in raiding salmon traps

AbstractIn the Baltic Sea there is a severe conflict between small-scale fisheries and gray seals. One fishery severely affected by seal predation is the salmon trap fishery. Underwater cameras were placed in two pontoon traps to study the behavior of raiding gray seals. Seals observed on film were identified and a catalog of ‘problem’ seals was created, totaling 11 individuals. As part of this study, 8 pontoon traps modified for live-trapping raiding seals were set out in the same area. Trapped seals were killed and their markings photographed in order to try to match them with seals in the catalog. The eleven identified seals were responsible for 426 out of 600 visits to the two traps with cameras. Four of the eleven seals raided at least two traps and returned to raid traps frequently over the 2-year study period. Seals caught in the pontoon traps modified for live-trapping were mainly adult male seals. Three of these seals were identified as cataloged seals. This study has shown that it is generally adult male gray seals which have specialized in raiding fishing gear. These specialist seals have developed a characteristic behavior pattern and have persisted with it over a long period of time