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Experimental Study on the Fish Preference for Hydraulic Environments

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  027004,  2002 ASAE Annual Meeting . (doi: 10.13031/2013.10305) @2002
Authors:   Kazuaki Hiramatsu, Shiomi Shikasho
Keywords:   Preference intensity model, Japanese Medaka Fish, environmental factor, laboratory experiment

The preference intensities of river fish to environmental factors were discussed in this paper. The three environmental factors of water depth, current velocity and cover were selected as the principal factors affecting the availability and quality of the fish habitat in natural rivers. Japanese Medaka Fish (Japanese killifish, Oryzias latipes) was selected as a river fish subject to quantify preference intensities because Japanese Medaka is now regarded as the symbolic fish for the restoration of countryside ecosystems in Japan.

Mathematical models for preference intensities of Japanese Medaka to the three environmental factors were constructed in laboratory open-channel experiments. A simple genetic algorithm was newly introduced to search for the optimal functional representation of preference intensity and to determine parameter values of the preference intensity models. The results indicated that the maximum preference level of Japanese Medaka was determined at a water depth of 9.4 cm and at a current velocity of 2.8 cm/s, and that the All-cover condition had a markedly high level compared with other cover conditions. The relative weights necessary for calculating the combined preference level of the three environmental factors were evaluated as 0.32 for depth, 1.0 for velocity and 0.66 for cover, when the maximum weight was normalized to be unity. The weight values suggested that the current velocity has the strongest preference intensity among the three environmental factors and that the environmental preferences of Japanese Medaka were not greatly affected by water depth.

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