Re-introduction and re-enforcement of oily bitterling in conjunction with local communities in Northern Mie, Japan

Summary

The oily bitterling (Tanakia limbata), a Near Threatened cyprinid fish dependent on freshwater mussels as spawning hosts, had nearly disappeared from the traditional satoyama farm ponds of Northern Mie, Japan, due to agricultural decline, pond siltation, eutrophication and invasive largemouth bass, until researchers from Nagoya University and Gifu-keizai University found just two surviving individuals at Kusune-tame pond in 2005 and launched a restoration project built around local community participation rather than agency-led management alone. The team bred roughly 300 bitterlings in a spring-fed concrete pool from an initial 23 wild-caught fish, then organized traditional pond-draining and drying events, ikehoshi, involving local residents, students and civil servants: an October 2005 draining at Kusune-tame pond removed 262 largemouth bass and recovered native mussels and bitterling, and a January 2008 draining at neighboring Kanshiro-tame pond, with about 200 residents, removed 1,100 bass. In April 2008, local children released 100 captive-bred bitterling alongside native gobies and other rescued fish into the restored pond, with further drainings and releases continuing through 2010. The project expanded into school biodiversity lectures, drew 500 participants from 50 countries during a 2010 UN biodiversity conference event, and earned Japanese government agricultural and environmental recognition. Persistent problems included repeated illegal re-releases of largemouth bass and other non-native fish by anglers and well-meaning residents, undermining eradication gains. The project rates itself Partially Successful, describing sustained bass reinvasion as an unresolved threat and the broader conservation effort as still only beginning.