Otter Lutra lutra damage at farmed fisheries in southeastern Poland, I: an interview survey

Fish farmers were interviewed on the occupancy and impact of otters Lutra lutra at common carp Cyprinus carpio fisheries in southeastern Poland during a preliminary survey in 1994–1995 and in 2003. Otters occurred at 104 (91%) of 114 surveyed fisheries, and in 71 (62%) fish farms the perceived otter predation pressure increased over the last decade. Of the interviewees, 65 (57%) reported serious losses to otters, and of these 51 (78%) claimed to have no otters or to have had the otter problem under control in the mid-1990s. The most frequently listed type of damage was killing or serious injuring of the commercially most valuable brood fish and surplus killing of cultured carps. Nondestructive attempts to protect stocks from otters were reported only exceptionally. Of the farmers with depredation problems, 17% admitted that illegal otter killing occurred at their farms. Field surveys revealed that fish farmers correctly identified otter presence at their ponds. However, farms differing in the perceived otter impact on cultured stocks did not differ in their annual overall fish losses. Private pond owners perceived losses to otters as higher than managers of state-owned fisheries. Spraint analysis at two intensively monitored adjacent fish farms, one with perceived serious economic losses and one which reported a minor otter problem, showed similar proportion of carp by weight (44 vs 41%, respectively) in otter diet.