GA-based model optimization for preference intensity of Japanese Medaka Fish (Oryzias latipes) to streamflow environments

Abstract

The preference intensities of Japanese Medaka Fish (Japanese killifish, Oryzias latipes) to the three environmental factors of water depth, current velocity, and cover are discussed in this paper. Mathematical models of preference intensities for Japanese Medaka Fish to the three environmental factors were constructed in laboratory open-channel experiments. A simple genetic algorithm for the optimal functional representation of preference intensity was introduced. The models were then verified by on-the-spot examinations. The results indicated that the maximum preference level of Japanese Medaka Fish was a water depth of 9.4 cm and a current velocity of 2.8 cm/s. The all-cover condition was considerably high compared with other cover conditions. The relative weights of the three environmental factors were 0.32 for depth, 1.0 for velocity, and 0.66 for cover, when the maximum weight was normalized. The weight values suggested that the environmental preferences of Japanese Medaka Fish were not greatly affected by water depth. Judging from the agreement between the predicted and observed distributions in considering the two factors of current velocity and cover, these two factors obviously affected the environmental preferences of Japanese Medaka Fish.