アイソザイム遺伝標識による放流湖産アユの追跡

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The amphidromous form of ayu Plecoglossus altivelis is distributed in Japanese natural rivers flowing into the sea, and the landlocked form is restricted in the freshwater lakes. The latter form has a spawning season two months earlier than the former form. We investigated the ayu in Monobe river using isozyme markers, i.e. Gpi-1 and Mpi loci, and gonado-somatic index (GSI). The Gpi-1100 and Mpi100 allele frequencies of amphidromous form were 0.626 and 0.874 respectively, and those of landlocked form 0.343 and 0.390 respectively, were examined as a control. The samples which were collected from three sites of Monobe river showed that the allele frequencies of Gpi-1100 ranged from 0.525 to 0.652 and Mpi100 from 0.600 to 0.957 res-pectively. The samples from two sites of lower reaches did not include the landlocked form, and showed the lower GSI value. The higher GSI groups of third site of upper reaches was identi-fied as a landlocked form, and the lower GSI groups was identified as an amphidromous form based on the allele frequencies of Gpi-100 and Mpi100. We concluded that the released fish of landlocked form disappear on the lower reaches of Monobe river at the beginning of September (in the spawning season of landlocked form). This is evidence that the landlocked form released on the lower reaches may be almost caught or finished its spawning. It was discussed that the released landlocked form of lower reaches might scarcely take part for the reproduction in the area of amphidromous populations.
日本水産學會の論文

アイソザイム遺伝標識による放流湖産アユの追跡

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