Relationships between the spot patterns on the head of the Japanese Char Salvelinus leucomaenis, distributed in the Chugoku Region, and water quality

Abstract

Head spots of chars were examined for 17 rivers of the Chugoku Region, and relationships between the patterns and water quality were analyzed. To enable quantitative comparison, two spot indices, index I, a ratio of the length to the width for the longest spot, and index II, a ratio of the width of the widest spot to the interorbital width, were calculated. Both spot indices were divided into three ranges, and all char specimens were categorized into eight types, from A to H. Type A with short and wide spots was the most dominant in the Nishiki, Gono and Hii Rivers in the central part of the Chugoku Mountain Chains whereas type H with long and narrow spots was the most dominant in the Gamo River in the eastern part. Electrical conductivity of the water showed a significant positive relationship to index I whereas it showed a significant negative relationship to index II. In contrast, Fe²⁺ concentration of the water showed a significant negative relationship to index I whereas it showed a significant positive relationship to index II.