2016 Volume 21 Issue 3 Pages 81-90
It was once thought that shooting could not reduce cormorants in number and population control was inappropriate for the species. However, a science-based population control by “sharpshooting”, systematical removal by a small team of professionals with highly specialized skills (cullers), proved that the effective management of cormorant populations was achievable. In the Lake Biwa and the surrounding rivers in Shiga Prefecture, Great Cormorants cause serious damage to fisheries as well as to ecosystems of their colonies including vegetation destruction and soil erosion. Despite various damage controls, both the cormorant population and the damage kept increasing. We conducted large-scale cormorant removal as a public project under the Fisheries Management Division of Shiga Prefecture. We removed 54,585 birds during 165-day operations, with two or three cullers a day (a total of 373 man-days), in two main colonies (the Chikubu-shima Island and the Isaki Peninsula) in the six breeding seasons of 2009-2015. As a result, the cormorant populations in Shiga in the early (May) and late (September) breeding season decreased from 37,066 (2008) to 7,659 (2015) and from 74,688 (2008) to 5,940 (2015), respectively. In conjunction with this decline, the fishery damage was reduced and the damaged ecosystem was restored. Due to this, fewer people now are of the opinion that cormorants should be exterminated. The locals who suffer from cormorants have begun to think that they could live with the birds if moderate in numbers. The large-scale removal by sharpshooting is realizing the goal of coexisting with cormorants, which we should aim at.
