We examined the effectiveness of energetic potential (net energy intake [NEI]) estimated from bioenergetics models as an index of habitat quality for stream salmonids in seven streams within four watersheds in Hokkaido, northern Japan. In addition, we confirmed the utility of the NEI as an index of habitat quality by comparing it with several other habitat variables, including pool volume, pool area ratio, and prey density, that are often used as indices of habitat quality for stream salmonids. The mean NEI at each study reach was closely related to salmonid abundance, although the physical environment and drifting prey density differed considerably among study sites. In contrast, the relationships between habitat variables and fish abundance were weaker (drift density) or nonsignificant (pool volume and area). These results suggest that the NEI is more widely applicable as an index of habitat quality for drift‐feeding fish, although its validity should be tested in additional systems.
Since the late 20th century, the biomass of Pacific salmon Oncorhynchus spp. has increased. Hokkaido, northern Japan, is one of the main areas of chum salmon O. keta production in the North Pacific and intensive hatchery programs support the recent high abundance. However, proper management of naturally spawning populations is necessary to conserve healthy stocks of this species. In 2008, we started a program to assess the naturally spawning chum salmon populations in Hokkaido. Of the total of approximately 1,500 rivers in Hokkaido, 238 rivers with lengths of longer than 8 km (excluding those rivers used for hatchery broodstock collection) were surveyed in 2008 and 2009. The number of nonenhanced rivers found to contain naturally reproducing chum salmon was 59 (31.4% of surveyed rivers) and 50 (37.6% of surveyed rivers) rivers in 2008 and 2009, respectively. Including the rivers where hatchery broodstock were collected and rivers shorter than 8 km that contain naturally spawning chum salmon, chum salmon ascended at least 191 and 175 rivers in Hokkaido in 2008 and 2009, respectively. Repeated foot surveys indicated that the run timings of naturally spawning chum salmon may be affected by coastal commercial fisheries. This study showed that naturally spawning chum salmon remain in many rivers in Hokkaido where hatchery programs have been intensively conducted.
1. The effect of ubiquinone (CoQ(9)) on ascites in broiler chickens was investigated. 2. The commercial broilers were divided into 2 groups of 100 birds each; CoQ(9) treated group and non-treated group. 3. The chickens were grown in a positive-pressured house with double high efficiency particulate air filtered intakes and exhaust, and thus were strictly isolated from infectious agents. 4. The chickens (15 to 21 d old) were exposed to cold stress in order to induce ascites. 5. The number of birds with ascites in the CoQ(9)-treated group was significantly lower than in the non-treated group. 6. Survival and production rates were better in the CoQ(9)-treated group than in the non-treated group.
This book that contains 38 research articles on marine ecology of Pacific salmon and steelhead trout, is dedicated to the International Year of the Salmon and is the first scientific publication that contributes to the library of the project.
Recreational fishing for masu salmon Oncorhynchus masou has recently become popular in coastal areas of south-western Hokkaido, including the Iburi district. We sampled recreational party boats in the Iburi district in the winters of 1998-1999 and 1999-2000. Daily numbers of anglers and catches of masu salmon were provided by the captains of the fishing boats. On average, anglers caught approximately four masu salmon per day each year, and peak catches occurred from late January to early February. Estimated numbers (standard errors in parentheses) of masu salmon caught by recreational anglers in the Iburi district were 66 844 (11 685) in 1998-1999 and 57 454 (6559) in 1999-2000, equivalent to 12-13% of the total annual commercial catches of masu salmon in Hokkaido. High recreational catches illustrate the importance of evaluating this fishery in the assessment and management of masu salmon in Hokkaido.
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