Current Genetic Status of Nagaremon-charr, a Threatened Morphotype of in the Ane River, Lake Biwa System, Central Japan, With Comments on Its Conservation.

Stream-dwelling white-spotted charr, , populations tend to have unique color and spot patterns in different regions and may even display stream-specific patterns. An extreme edge of such diversity, found in individuals with atypical body color patterns (so-called nagaremon-type charr, a rare morphotype of [hereafter termed nagaremon-charr]), sympatrically occurring with normal-charr, has been reported from only six small isolated populations in Japan. Based on morphological and ecological perspectives, nagaremon-charr has been considered as an intraspecific color variant of white-spotted charr, although the genetic status of nagaremon-charr has not been determined.

Daily growth increments in otoliths of wild-caught honmoroko Gnathopogon caerulescens.

Otolith growth increments in wild-caught alizarin complex one (ALC)-marked honmoroko Gnathopogon caerulescens were examined to verify the veracity of the age determination method in cyprinids. ALC-marked G. caerulescens recaptured from their natural environment had lapilli increment counts outside the ALC ring mark that had formed on a daily basis during the juvenile stage.

Iteroparity of stream resident masu salmon Oncorhynchus masou.

The degree of iteroparity in stream-resident forms of masu salmon Oncorhynchus masou was examined using mark-recapture studies in natural streams. In a partially migratory population, at least 10% of resident males survived after maturation and repeatedly matured for up to 5 years. In the landlocked amago salmon subspecies, the post-maturation survival rate was at least 7% and repeat maturation was observed for up to 3 years for both males and females.

Mitochondrial DNA population structure of the white-spotted Charr (Salvelinus leucomaenis) in the Lake Biwa water system.

A phylogeographic analysis of mitochondrial DNA sequences was performed in order to elucidate the origin, dispersal process, and genetic structure of white-spotted charr in the Lake Biwa water system. Two haplotypes were most common in the Lake Biwa water system, and were also common in the adjacent inlet rivers of the Sea of Japan. These results suggest that in the glacial periods of the Pleistocene, white-spotted charr dispersed into the northern inlet rivers of Lake Biwa from adjacent inlet rivers of the Sea of Japan by watershed exchanges, colonizing the whole of the Lake Biwa water system.