Taiga Yodo* and Kei'ichiro Iguchi. 2003. Feeding habits of introduced smallmouth bass in Lakes Aoki and Nojiri, Japan. Japan. J. Ichthyol., 50(1): 47-54. Abstract To elucidate the feeding habits of smallmouth bass Micropterus dolomieu in Japanese inland waters, the stomach contents of fish from Lakes Aoki and Nojiri, Nagano Prefecture, differing in catchment landscape, were analyzed. Specimens were collected from May 2000 to October 2001 in Lake Aoki and from June to December 2000 in Lake Nojiri. Prey importance was estimated from an index of relative importance (IRI, (percent of prey number+percent of prey weight) ~frequency of prey occurrence). The main prey in Lake Aoki were pond smelt (Hypomesus nipponensis) and a cyprinid (Tribolodon hakonensis), and in Lake Nojiri, a shrimp (Macrobrachium nipponense) and goby (Rhinogobius sp.). Aquatic and terrestrial insects were also important prey in spring and summer in both lakes. Principal prey changed ontogenetically from small bottom-dwelling animals (gobies or aquatic insects) to larger limnetic fish in both lakes. The results suggested that smallmouth bass will have deleterious effects on differing animal groups with growth. *Corresponding author: Japan Society for the Promotion of Science Domestic Research Fellow, National Research Institute of Fisheries Science, 1088 Komaki, Ueda, Nagano 386-0031, Japan (e-mail:)
Table 1. Number and stundard length of smallmouth bass examined in the study
Table 2. Stomach contents of smallmouth bass in Lake Aoki
Table 3. Stomach contents of smallmouth bass in Lake Nojiri Table 4. Index of relative importance (IRI) of prey categories for smallmouth bass in Lakes Aoki and Nojiri AI, aquatic insects; BF, bottom-dwelling fishes; C, crustaceans; LF, limnetic fishes; TI, terrestrial insects.
Table 5. Factor loadings of principal components (PC 1-3) of weight to stomach content ratios for each prey category in smallmouth bass in Lake Aoki AI, aquatic insects; HN, Hypomesus nipponensis; TH, Tribolodon hakonensis; TI, terrestrial insects. Table 6. Factor loadings of principal components (PC 1-4) of weight to stomach content ratio for each prey category in smallmouth bass in Lake Nojiri AI, aquatic insects; BF, bottom-dwelling fishes; C, crustaceans; LF, limnetic fishes; TI, terrestrial insects.
Fig. 1. Monthly changes in the indices of relative importance of prey of smallmouth bass. Limnetic fishes ( œ), bottom-dwelling fishes ( Z), crustaceans ( ), terrestrial insects ( ), and aquatic insects ( ). Fig. 2. Relationships between standard length of smallmouth bass and principal component analysis scores.
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