Morphology, stomach contents and growth of the endangered salmonid, Sakhalin taimen Hucho perryi, captured in the Sea of Okhotsk, northern Japan: evidence of an anadromous form

Abstract

We describe a total of 25 anadromous Sakhalin taimen Hucho perryi collected on the coast of Sarufutsu, northern Hokkaido, Japan in June 1997 and 1999. We examined morphology, stomach contents and growth of three anadromous taimen (one male and two females) in detail, which were preserved in good condition. The three taimen were aged and one female still had some eggs retained in her abdomen. The stomach contents of the three taimen consisted of sand lance Ammodytes personatus Girard and sculpin Triglops sp. On the basis of scale analyses, the growth rate of the three taimen was estimated by using the back-calculation method, and the highest rates were observed at young ages. Guanine pigmentation was present at the base of the caudal fin of each taimen and is considered as a potential morphological trait to differentiate anadromous from fluvial specimens. Another anadromous taimen, of which some individuals had reared for more than 3 years in seawater are also reported. For the conservation of this rare and endangered species, their migration route between rivers and sea should be protected