Nippon Suisan Gakkaishi 68 (6), 852-858 (2002)

Stock separation study using otolith Sr/Ca ratio on ayu Plecoglossus altivelis captured from the Ioki River and the Monobe River

SATORU SEIKE,1 MASAYA OKABE,2 AKIRA SAEKI,2 TETSUYA UMINO,1
TSUGUO OTAKE3 AND HEISUKE NAKAGAWA1

1Faculty of Applied Biological Science, Hiroshima University, Higashi-hiroshima, Hiroshima 739-8528, 2Kochi Prefectual Freshwater Fishies Experimental Station, Tosayamada, Kochi 782-0016, 3Faculty of Bioresources, Mie University, Tsu, Mie 514-8507, Japan

A stock separation study on ayu Plecoglossus altivelis captured from the Ioki and the Monobe rivers was conducted using the otolith Sr/Ca concentration ratio method. Discrimination among amphidromus, hatchery-cultured and landlocked populations was possible by comparing with chart patterns during early life stage, because the rearing salinity of hatchery-cultured fish is intermediate between those of amphidromus and landlocked populations. When stock separation was carried out by both otolith Sr/Ca ratio and mark-releasing with 85 individuals, disagreement between them occurred for only 9 individuals. It is indicated that stock separation by the method of otolith Sr/Ca ratio is as effective as the conventional mark-releasing method.


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