No.61(March,2002)
No.85(Maruch,2014)
A-500 Shiro TAKAYANAGI and Tadashi MISAKA
Variation in the maturity size of the Japanese sea cucumber, Apostichopus japonicus, by macroscopic observation, in the coastal waters of Hokkaido, Japan
Variation in the maturity size of the Japanese sea cucumber (
Apostichopus japonicus) collected in the coastal waters around Hokkaido, Japan, was assessed. From 2006 to 2009, 2,978 specimens were collected during June and August from 10 localities and examined by macroscopic observation. Differences are found in maturity curves and 50% maturity size (body wall weight) in the different coastal waters. Based on generalized linear mixed model (GLMM) analysis using the obtained maturity for each individual as a response variable, the optimal model divided the 3 coastal waters into the Sea of Japan (including the Tsugaru Strait), the Sea of Okhotsk and the waters of the Nemuro Strait and the Pacific Ocean (Hidaka area). The estimated 50% maturity body wall weight was 97.5 g, 76.1g, and 64.1g for each area, respectively.
A-501 Atsushi NOMURA，Tetsurou KUBO，Osamu SHIDA，Kazuhiko ITAYA，Yasushi ITO and Yasunori SAKURAI
Feeding habits of juvenile walleye pollock, Theragra chalcogramma, in waters of the western Hokkaido, Japan Sea in August and October 2011
Feeding habits of juvenile walleye pollock, Theragra chalcogramma occurring in waters of the western Hokkaido, Japan Sea collected in August and October, 2011 were examined by the stomach contents analysis. The main stomach content items were Themisto japonica, Metridia pacifica and Euphausia pacifica. The monthly analysis showed that the index of relative importance (IRI) of T. japonica was high in August and low in October. On the contrary, IRI of M. pacifica and E. pacifica were high in October. It is observed that IRI of the main stomach content items among the sampling stations were also different.
A-502 Yoshiyuki TAKAYA and Nobukazu SATO
Relationships between the specific growth rate and biochemical constituents in the trunk of laboratory-reared juvenile barfin flounder, Verasper moseri
Relationships between the specific growth rate (SGR) and biochemical constituents in the trunk of juvenile barfin flounder (Verasper moseri) were investigated. The juveniles were reared for 25 days under 2 dietary conditions (0.5% and 2% body weight day-1, respectively), to clarify the biochemical constituents, for use as the substitute indicators for SGR. Specifically, we analyzed moisture, crude fat, triglyceride, phospholipid, glycogen, protein, RNA, DNA, and free amino acid levels after feeding. Crude fat, moisture, RNA/DNA ratio, phospholipid/DNA ratio, and protein/DNA ratio exhibited positive linear regressions with SGR. Our results show that these biochemical indicators may be potentially useful as a substitute index for SGR when evaluating the growth rate of released barfin flounders in the field.
A-503 Naoyuki MISAKA, Shinya MIZUNO, Daisei ANDO, Tatsuya KOYAMA, Tetsuo TERANISHI and Nobuhisa KOIDE
Effects of cottonseed oil in diets on growth, feed efficiency and health parameters of chum salmon Oncorhynchus keta fry
We evaluated the effects of replacing fish oil in diets with cottonseed oil on chum salmon
Oncorhynchus keta fry. Chum salmon fry were fed commercial
diets supplemented with 0.5% or 2.0% fish oil (0.5FO, 2.0FO) or cottonseed oil (0.5CO, 2.0CO) for two to three months in aquariums in 2005 and 2006 to compare parameters between 0.5FO and 0.5CO, 2.0FO and 2.0CO diet groups, respectively. In 2005, fish fed 0.5CO diet for three months, 2.0CO diet for two and three months showed significantly better growths. Feed efficiencies of fish fed 0.5CO and 2.0CO diets were almost better both in 2005 and 2006. The ATP contents of fish fed 0.5CO and 2.0CO diets for two months were significantly increased both in 2005 and 2006. Burst swimming velocities of fish fed 0.5CO and 2.0CO diets for two months were significantly faster in 2006. Tolerances to fasting were significantly higher in fish fed 2.0CO in 2005, 0.5CO and 2.0CO in 2006. These results suggest that supplementing the diet with cottonseed oil is effective for improving the growth, feed efficiency and health parameters of chum salmon fry.
Age-9 chum salmon caught in eastern Hokkaido (Short Paper)
Chum salmon
Oncorhynchus keta usually mature at two to six years of age (i.e., age 0.1-0.5 in the European system), and recently the existence of age-7 and age-8 chum salmon has been reported. For management of fisheries and enhancement of this species, the Salmon and Freshwater Fisheries Research Institute examines the age of chum salmon returned to rivers and coastal areas of Hokkaido. An age-9 chum salmon was found in fish caught in the set-net fishery in the Utoro area, eastern Hokkaido, on 12 September 2012. The fish was male, and scales were only sampled but the body size was not measured. From the scale length, fork length of the fish was estimated at 67.5 cm (95% confidence interval: 66.8-68.2 cm). This is the first record of age-9 (age 0.8) chum salmon in Japan.
Estimation of number of downstream migrating chum salmon fry in the Nishibetsu River in 2006 (Short Paper)
Marked chum salmon
Oncorhynchus keta fry (n = 104,200) with a clipped right pelvic fin were released in the upper reaches on 28 April, and were recaptured with a rotary screw trap in the lower reaches of the Nishibetsu River, eastern Hokkaido, northern Japan in 2006. A total of 23 marked fish were recaptured between 5 and 26 days after release. To assess the trap efficiency, chum salmon fry clipped upper the lobe of the caudal fin (n = 5,970) were released at the 2 km upper the trap, and seven fish were recaptured; trap efficiency was estimated at 0.13%. Right pelvic fin clipped chum salmon fry that passed the trap site were estimated at 17,167; the rate of recaptured fish against released fish was estimated at 16.5%
Distribution of masu salmon redd in the Doudoromappu River, a tributary of the Abashiri River, before and after the construction of fish ways (Short Paper)
We investigated the distribution and number of spawning redds of masu salmon
Oncorhynchus masou in the Doudoromappu River, a tributary of the Abashiri River in Hokkaido seven years before and after the construction of fish ways. Although the distribution of spawning redds had expanded into the upper reaches of the river, the total number of spawning redds had not increased in one to three years after the construction of fish ways. Four to five years after construction, the total number of spawning redds had increased by 2.6 times as many as that of their parents generations. According to previous reports, the population densities of juvenile fish were high in the year after construction of the fish ways, and the mortalities of eggs were high in the upper reaches of the river. We supposed that expansion of the habitat and spawning area by construction of the fish ways might lead to high mortalities of eggs and juveniles, and increase the number of seaward migration fish and ascending adults.
