Stock identification of chum salmon Oncorhynchus keta from their maturity and scale chraracters.

Abstract

The origin of four-year-old chum salmon caught in the Bering Sea in July, 1981 was estimated from their gonad weight and scale characters. There were three different maturity groups in the gonad weight frequency distributions for both female and male chum salmon. The maturing group with lower gonad weight (MT2) had more circuli and narrower width of the first year zone of the scale than those of the immature group (MT1) and the maturing group with higher gonad weight (MT3). A comparison of the scale characters of these three groups with those of chum salmon caught in the coastal regions showed that the MT1 group was similar to U.S.S.R. and Japanese chum salmon, the MT2 group was similar to Japanese chum salmon, and the MT3 group was similar to U.S.S.R. chum salmon. This suggests that different maturity groups in the high seas catch correspond to stocks from different geographical regions.