Threatened fishes of the world: Kirikuchi charr, Salvelinus leucomaenis japonicus (Oshima 1961) (Salmonidae)

Abstract

Common name: Kirikuchi (Japanese). Conservation status: Kirikuchi char (Salvelinus leucomaenis japonicus) is the southernmost population of the genus Salvelinus. Isolated from the main rivers in the drainages (Endangered, IUCN 1996; Threatened local populations, Tanaka 2003 Red Data Book of Japan 2003). Parts of the natural habitat have been designated as the natural protected area of Nara Prefecture. Identification: Kirikuchi char constitute geographically and genetically distinct local populations of Yamato char S. leucomaenis japonicus, a subspecies of the typical Japanese char S. leucomaenis leucomaenis, which belongs to a different clade of the Yamato char in a maximum parsimony tree of haplotypes (Yamamoto et al. 2004). Kirikuchi char differ morphologically from other Japanese chars: they have reddish golden bodies, few white spots on the lateral sides, darkish squash spots around the lateral lines, and relatively short snouts (Hosoya 2000). Photograph by Yuichi Kano. Distribution: Originally, Kirikuchi char were common in the Totsu and the Hidaka River systems in the Kii Peninsula, western Japan. However, only six small populations remain in the two upper drainages of the Totsu River system (34 5¢N, 135 33¢E; 34 13¢N, 135 53¢E), isolated from the main rivers in the drainages (Tanaka 2003, Sato & Watanabe 2004). Abundance: Its largest population comprises approximately 600 fish (100 mm and over in SL); the smallest, which might become extinct in the near future, comprises a few dozen individuals. Estimated effective population sizes of the largest two populations are not more than 100 individuals (Sato unpublished data). Habitat and ecology: Adapted to cold-water high mountain streams in which maximum temperatures are less than 18 C. Only the stream resident form has been observed. Specimens rarely reach 300 mm SL, and the average body size is approximately 160 –180 mm SL. Kirikuchi char preferably inhabit pools with refuges, woody debris and/or rocks, and feed mainly on aquatic and terrestrial insects. Reproduction: They spawn during October–November. Threats: Kirikuchi char face a high risk of extinction primarily from: (1) habitat deterioration by riparian forest logging or habitat fragmentation; (2) hybridization and competition with introduced non-native Nikko char S. leucomaenis pluvius, which has been commonly cultured and stocked in Japan; and (3) overharvesting, including poaching, by fishermen (Sato & Watanabe 2004). Moreover, because of their small isolated population structures, inbreeding depression might affect their viability. Conservation actions: Effective management measures have not been implemented, but a few volunteers are carrying out surveillance for prevention of poaching. Conservation education programs have also been launched for children of local communities. Conservation recommendations: Practical preservation techniques are urgently required for remaining populations. Habitat restoration, removal of non-native char, and re-establishment of new populations would be effective. Furthermore, rehabilitation of riparian forest is essential for conserving self-sustaining populations in the future. Remarks: Kirikuchi char is of biogeographical, evolutionary, and ecological interest.