Daisei Ando

Erratum to: An overview of salmon enhancement and the need to manage and monitor natural spawning in Hokkaido, Japan

The chum and pink salmon catches in Hokkaido, Japan have increased dramatically since the 1970s and the 1990s, respectively. In contrast, masu salmon catches have been steadily decreasing. Despite intensive hatchery development in Hokkaido, naturally spawning salmon populations persist based on results from a recent river survey. This paper focuses on the challenges of maintaining hatchery salmon populations while protecting natural chum, pink and masu salmon populations in Hokkaido. Two important initiatives related to meeting this ambitious goal are managing hatcheries in a way that minimizes negative interactions between natural and hatchery salmon populations, and initiating new efforts at restoring and rehabilitating degraded freshwater habitats. In addition, in order to maintain a balance of demand and supply in the domestic market through the exportation of extra salmon, Hokkaido has decided to enter full assessment to gain Marine Stewardship Council (MSC) certification of the Hokkaido chum salmon trap net fishery. This would involve a fundamental shift in fisheries management as practiced in Japan, specifically elevating the importance of managing the fishery in a way that conserves natural salmon populations. A key component of a new salmon management strategy is the establishment of a zone management framework based on the designation of stream units to spatially separate natural salmon from hatchery salmon to minimize negative effects of hatchery fish and to utilize effectively hatchery salmon for commercial fisheries. This effort is allied with similar initiatives in other Pacific Rim countries that are focusing on management reform to restore natural ecosystem function and maintain the coexistence of wild and hatchery salmon.

Estimation of heritability and genetic correlation of number of abdominal and caudal vertebrae in masu salmon

Ten sibship masu salmon Oncorhynchus masou masou families were produced to estimate the heritability of the number of abdominal vertebrae (AV) and caudal vertebrae (CV), and the genetic correlation between the two traits were calculated. The AV and CV of both the parents and their offspring were counted separately, and the heritability was estimated by performing parent-offspring regression analysis. The mean vertebral number of the offspring differed among families although they were reared under identical water temperature conditions and had the same parental vertebral number type in crossbreeding. The heritabilities were estimated as 0.65 for AV and 0.84 for CV. The genetic correlation between the number of AV and CV was calculated as −0.92. These results suggest that AV and CV are governed by genetic components even when the fish are reared under identical environmental conditions, and the total vertebral number is expected to converge within a certain range. It is necessary to analyze separately the variations in the number of AV and CV when investigating the vertebral number in masu salmon.

Quantitative changes of black pigmentation in the dorsal fin margin during smoltification in masu salmon, Oncorhynchus masou

We attempted establishment of quantitative system for dorsal fin pigmentation due to diffusion of melanin granules in melanophores during smoltification in masu salmon (Oncorhynchus masou) with image analysis and examined whether it is possible to determine the optimal time for smolt release of hatchery-reared masu salmon, which have many physiological characters in common with wild masu salmon, with the level of dorsal fin pigmentation. The effects of anesthesia with ethyl-m-aminobenzoate and fixation with paraformaldehyde on the pigmentation analysis were also investigated. There were no significant effects of 10-min full anesthesia or fixation on dorsal fin pigmentation. We were able to analyze dorsal fin pigmentation by observation of the fin within 10-min full anesthesia and in fixed fin tissue. Changes in dorsal fin pigmentation in hatchery-reared and two stocks of wild yearling masu salmon during smoltification from January or March to May in 2001 and 2002 were examined and compared with gill Na+,K+-ATPase activity. In both 2001 and 2002, the level of dorsal fin pigmentation and ATPase activity increased significantly from January or March to May during smoltification (P<0.05) in all fish. There was no significant difference in pigmentation level and ATPase activity in May among all fish in both 2001 and 2002. Means of the level of dorsal fin pigmentation in May for 2 years for all fish ranged between 83% and 84%. The earliest period, in which the pigmentation level began to increase significantly compared to initial period, was prior to the time, at which the ATPase activity increased, in all fish in 2001 and 2002. The levels of dorsal fin pigmentation and gill Na+,K+-ATPase activity exhibited a positive nonlinear correlation in wild and hatchery-reared fish. These observations suggest that the level of dorsal fin pigmentation could be used as an indicator of the suitable time for smolt release of our hatchery-reared masu salmon.

Quantitative Analysis of Body Silvering during Smoltification in Masu Salmon using Chromameter

Abstract In Japan, the phase distinction of masu salmon Oncorhynchus masou during smoltification is determined based on external appearance such as body silvering and black pigmentation of dorsal and caudal fin margin. This method is subjective, and it is difficult to quantify smoltification because body silvering and fin pigmentation level change continuously. Therefore, innovative and easily used criteria to establish smoltification are necessary. We therefore tested a chromameter (L-value) to measure body silvering in two brood years of hatchery-reared and natural (wild and hatchery-origin fish occurring in the wild) masu salmon and examined its effectiveness in determining the progress of smoltification as it relates to establishing smolt release time. Time required to measure body silvering using a chromameter was approximately 10 s per fish. For both brood years, the L-values of hatchery-reared and natural fish differed. With the progress of smoltification in both hatchery-reared and natural fish, t...

Seasonal variations in and effect of incubation water temperature on vertebral number in naturally spawning chum salmon Oncorhynchus keta

Seasonal variations and reaction norms for vertebral number (VN) in response to incubation water temperature were estimated in adult and juvenile naturally spawning chum salmon Oncorhynchus keta. The mean VN of adults varied according to spawning time; the early-spawning population had higher VN values than the late-spawning population. Moreover, the mean VN values in the early-spawning population decreased with seasonal changes, whereas VN values in the late-spawning population remained stable. Chum salmon embryos in three full-sib families were incubated at five different temperatures until hatching, and the VN values of the resulting juveniles were analyzed. The VN reaction norm to incubation water temperature showed a V-shaped curve that was lowest at an intermediate temperature. The mean VN at the same incubation temperature varied among the three families. These results suggest that VN values in chum salmon are influenced by genetic components and incubation water temperatures. VN may be a useful parameter for estimating the environmental conditions during ontogenesis and the genetic background by detecting population changes.

Seasonal distribution of yearling masu salmon released from the Sea of Japan side of southwestern Hokkaido, Japan

Abstract We investigated the seasonal distribution and migration patterns of hatchery-reared masu salmon Oncorhynchus masou in the area surrounding Hokkaido, the northern island of Japan. From 1993 to 1999, we tagged and released 313,000 yearling masu salmon smolts into the coastal waters of the Sea of Japan adjacent to southwestern Hokkaido. From May of the release year through July of the following year, a total of 1,693 fish were recaptured in the coastal waters of northern Japan. Just after their release, masu salmon juveniles had two migration routes; one group moved northward along the western side of Hokkaido in the Sea of Japan, while the second group passed through the Tsugaru Strait and then moved eastward into the Pacific Ocean. It was estimated that both groups reached the Sea of Okhotsk at 30–40 d postrelease. The summer distribution of tagged fish was unknown because none were recaptured. Young fish appeared in the Sea of Okhotsk again in autumn and then migrated southward, retracing the abo...

Estimation of heritability of vertebral number in chum salmon Oncorhynchus keta

Hereditary causes of variation in the vertebral number of chum salmon were analyzed to estimate heritability for populations in the Chitose and Shikiu Rivers, Hokkaido Island, northern Japan. A total of 70 families were produced by diallel cross mating and then heritability was estimated using two statistical tests: a two-way ANOVA and a parent-offspring regression. Heritability estimates ranged from 0.26 to 1.91 and showed a strong correlation between the values from the two different tests. Estimates from female components were substantially higher than those from male components, which can be attributed to the maternal effect. Heritability in the Shikiu River population was shown to be higher than that in the Chitose River population. These results indicate that the heritability of vertebral number in chum salmon is generally high, and also that vertebral number is controlled by hereditary causes.