Spawning site characteristics of Kirikuchi charr Salvelinus leucomaenis japonicus: southernmost population, and effects of angling pressure.

概要

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Population size and spawning site environment of the endangered southernmost population of Kirikuchi charr Salvelinus leucomaenis japonicus were investigated in a tributary on the upper reaches of the Totsu River system, Nara Prefecture, central Japan, in 2001. The total number of fish≥100 mm in fork length (FL) in May was estimated to be 308±50 (SE). Water depth and gravel size at spawning sites were 15±13 cm (meant±SD) and 31±8 cm, respectively. Spawn-ing sites were found mainly at upstream sites, freely accessible to the fish. The number of fish≥130 mm in FL had dropped in the lower section of the tributary in July, most probably as a result of leisure fishing. Spawning redds were clearly fewer in the lower sections than further upstream. These results indicated that fishing pressure on the population had been heavy, resulting in a decreased level of reproduction population.
日本魚類学会の論文