特定外来生物オオクチバスの違法放流 : 岩手県奥州市のため池の事例(保全情報)

抄録

We investigated the fish fauna in 50 irrigation ponds in Iwate prefecture, northeastern Japan. Four cases of new invasions of alien largemouth bass, Micropterus salmoides, into previously non-invaded ponds were observed during surveys from 2008 to 2009. Given the limitations of natural migration by largemouth bass, all of these cases were likely the result of illegal stocking. In three of the ponds, establishment of new populations of bass was successfully prevented by the removal of collected individuals during our survey. However, the population eradication in the remaining pond failed, and the recruitment of juveniles was observed in 2010 surveys. Our results suggest that the Invasive Alien Species Act was insufficient to prevent illegal stocking of largemouth bass and that further countermeasures such as monitoring surveys and patrolling are needed.