Latitudinal Gradient in the Body Weight of Bluegill Lepomis macrochirus in Lake Biwa, Japan

Yoshimasa Yamamoto ； Hajime Tsukada ； Daisuke Nakai

《Zoological Studies》 49卷5期 (2010/09) Pp. 625-631

並列摘要

Variations in the body weight of bluegill Lepomis macrochirus among 10 coastal regions of Lake Biwa and 11 lagoons of the lake were studied in Oct. 2005 and Oct. 2007, respectively. The body weights of fish with a normalized total length were estimated from length-weight relationships determined at each site. Body weights of bluegill from the lake and lagoons increased linearly with latitude. Additionally, there was a negative correlation between the calculated body weight and the number of sampled bluegill per unit time from the lagoons, implying that the population density of bluegill may strongly influence its growth in lagoons. Increasing numbers of submerged plants have covered the lake area in recent years, especially in the shallow southern basin. Moreover, as a predator of bluegill, the largemouth bass Micropterus salmoides appears to flourish at higher densities in the northern basin of the lake than in the southern basin. These biotic factors seem to be somewhat responsible for the significant difference between the northern and southern basins in terms of the body weight of bluegill. However, water temperature and population density of the bluegill appear to be more directly responsible for the latitudinal variation in bluegill growth in Lake Biwa.

並列關鍵字

Bluegill ； Body weight ； Length-weight relationship ； Latitude ； Lake Biwa