Cottus nozawae Snyder 1911

Amphidromous. Refers to fishes that regularly migrate between freshwater and the sea (in both directions), but not for the purpose of breeding, as in anadromous and catadromous species. Sub-division of diadromous. Migrations should be cyclical and predictable and cover more than 100 km.Characteristic elements in amphidromy are: reproduction in fresh water, passage to sea by newly hatched larvae, a period of feeding and growing at sea usually a few months long, return to fresh water of well-grown juveniles, a further period of feeding and growing in fresh water, followed by reproduction there (Ref. 82692).

Inhabits middle and upper reaches of rivers. MtDNA studies revealed three distinct phylogenetic groups (Hokkaido Island, Northern Tohoku District and Yamagata Prefecture) of the species. This also provides the basic information for the conservation of the species populations in the Tohoku District which have been designated as endangered local populations (Ref. 43190).

Cottus nozawae is a species of freshwater ray-finned fish belonging to the family Cottidae, the typical sculpins. It is found in southern Sakhalin Island in Russia, Hokkaido and northern Honshu in Japan and in the Korean Peninsula. It reaches a maximum length of 6.9 cm. This species was first formally described in 1911 by the American ichthyologist John Otterbein Snyder with its type locality given as the Ishikari River at Sapporo on Hokkaido. This species is sometimes placed in the subgenus Cephalocottus. The specific name honours zoologist Shunjiro Nozawa, Director of the Fisheries Bureau on Hokkaido.