The relationship between mean weights of hatchery-reared masu salmon Oncorhynchus masou smolts at release and the subsequent recovery rates by coastal commercial fisheries in Hokkaido, northern Japan, was investigated using the maximum likelihood method. A strongly positive correlation was observed, showing smolts with a mean of 32.6 g obtained an approximately 20-fold recovery rate of those with a mean of 14.8 g. The model with log-transformed independent variable (Y i = -11.237 + 4.239 ln X i ) was selected as the most parsimonious model to represent the release size (X i ) and recovery rate (Y i ) relationship. KEY WORDS: Akaike information criterion, masu salmon, maximum likelihood method,Oncorhynchus masou, smolt size.

A review of Pacific salmon hatchery programmes on Hokkaido Island, Japan. e ICES Journal of Marine Science, 63: 1353e1363.Hatchery programmes involving the mass release of cultured fish have been implemented worldwide to supplement wild populations and to increase harvests. Hokkaido Island is one of the most active regions for Pacific salmon hatchery programmes, with ca. 1.2 billion (10 9 ) juveniles released annually along a coastline of ca. 3000 km. During the last quarter of the 20th century, coastal catches of chum and pink salmon increased dramatically, whereas those of masu salmon did not. In addition to the development of hatchery technologies, several possible hypotheses may explain these catch trends, including climate change, closing of high-seas fisheries, rehabilitation of water quality, habitat loss caused by damming and channelling, and increased pressure from recreational fisheries. Even when these other factors have been accounted for, it is difficult to evaluate whether all hatchery programmes have actually increased net populations. To use these programmes more effectively, it is necessary to evaluate both their river-and species-specific benefits and compare hatchery programmes with other management tools, such as fishery controls and habitat rehabilitation. Future hatchery programmes should incorporate active, adaptive learning approaches to minimize the risks associated with artificial propagation and to promote sustainable salmon stocks.

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To clarify the genetic relationship between Swamp and River buffaloes, the restriction fragment length polymorphisms (RFLPs) of nuclear genomic ribosomal DNA (rDNA) and cytoplasmic mitochondrial DNA (mtDNA) were analysed. Blood or liver samples from 73 Swamp and three River buffaloes were collected in East and South-east Asian countries. DNA samples from cattle, goats and sheep were used for comparisons. The analysis of rDNA allowed water buffaloes, cattle, goats and sheep to be characterized by four distinct repeat-types. However, swamp and river buffaloes showed the same repeat-type. Divergence of water buffalo and cattle is considered to have occurred approximately four to six million years ago. The RFLPs for mtDNA divided water buffaloes into three haplotypes, swamp-1, swamp-2 and river types. Swamp-1 accounted for 91% of all swamp buffaloes while swamp-2 was observed only in water buffaloes from Thailand (9%). All river buffaloes were of the same haplotype. No differences were observed between swamp and river buffaloes at the rDNA level. In contrast, a few distinct differences between them were found at the mtDNA level. Therefore, mtDNA polymorphisms provide an adequate means for classifying water buffaloes into either swamp or river buffaloes.