徳島県勝浦川に生息する魚類の出現/非出現の予測モデル

抄録

A series of investigations to study the relationship between the habit of stream fishes and physical environmental factors was conducted during 1999-2000 in the upper reach of the Katsuura River, Tokushima Prefecture. A semi-quantitative method (applied line-transect) was applied, and the occurrence/non-occurrence of each fish species recorded. Logistic regression models were constructed using binary fish data as objective variables and 15 physical environmental factors as predictor variables. The models were evaluated from the aspect of predictability involving both occurrence and non-occurrence of fishes. Although the models obtained for 18 of the 20 species in the area were significant, the models for only seven species were appropriate for predictability. For other species, the occurrence ratios indicated either extremely low or extremely high values. A few models, such as that for Oncorhynchus masou ishikawae, however, indicated sufficient predictability regardless of a low occurrence ratio.