Relationships Between the Spot Patterns on the Head of the Japanese Char, Salvelinus leucomaenis, in the Chugoku Region, and Altitude or Riverbed Gradient

Abstract

We examined head spots of chars in rivers of the Chugoku Region, Japan and analysed relationships between the spot patterns and altitude or riverbed gradient. We compared the spot shapes quantitatively with 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 interobital width. We divided all the char samples into two groups, the Gogi and the Nikkoiwana, according to earlier publications on their distributions. Index I showed a significant negative relationship to altitude for the Gogi group whereas it showed a significant positive relationship for the Nikkoiwana group. On the other hand, index I showed no significant relationship to gradient for either group. Index II showed no significant relationship to altitude for either group. In contrast, index II showed a significant negative relationship to gradient for the Gogi group whereas it showed no significant relationship for the Nikkoiwana group. These results suggest that the Gogi has morphologically adapted to the above environmental factors in a different direction from the Nikkoiwana.