Each redd of the Sakhalin taimen Hucho perryi had a V-shaped pot that is specific to this species. The shape of each multiple-egg-pocket redd was a combination of one-egg-pocket redds, and the number of egg pockets in the redd could be estimated from the shape. False redds were small and did not have any V-shaped pots. The factors affecting redd size were examined numerically; consequently, numbers of egg pockets and eggs and female fork length were correlated significantly with tail length. Each egg pocket contained 11-920 eggs (mean: 546·7 95% CL 81·9) and the egg pocket depth was correlated significantly with female fork length. Mean number of redds per female was three, and the number of females could be estimated as one third of the redds. 2000 The Fisheries Society of the British Isles

SynopsisWe 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.

ABSTRACT:To develop a suitable cryopreservation diluent for spermatozoa of the endangered Sakhalin taimen Hucho perryi, all possible combinations of cryoprotectants (glycerol, dimethyl sulfoxide [OMSO], methanol) and extenders (fetal bovine serum [FBS], 300 mM glucose solution [GS], artificial seminal plasma for masu salmon) were examined by observing sperm motility 10 s after thawing. Spermatozoa cryopreserved with diluents such as mixtures of 10% glycerol plus 90% FBS, 10% OM,SO plus 90% FBS, and 10% methanol plus 90% GS showed the highest motility. The maximal post-thaw motility was observed at 10% among all concentrations (0, 5,10,15 and 20%) of these three cryoprotectants. No significant difference among three diluents was observed in motility at 10 s, Mixtures of 10% glycerol plus 90% FBS, 10% OMSO plus 90% FBS, and 10% methanol plus 90% GS are suitable cryopreservation diluents for Sakhalin taimen spermatozoa.

Final instar larva, young larva and pupa of Oxyethira acuta KOBAYASHI are described. Young larvae do not make the case. Final instar larvae bear bottle-shaped cases made entirely of silk. The larvae live on the stems and leaves of higher water plants and feed on the filamentous green algae. They break the cell walls of the algae by their mandibles and suck out the cell contents. O. acuta has a one year life cycle in Lake Utonai, Hokkaido, northern Japan; young larvae occur in late summer, final instar larvae are found from early autumn to next summer, and pupae occur in summer.