Growth of large and small forms of pond smelt Hypomesus nipponensis in Lake Kasumigaura, Japan

Abstract

Growth formulae of two forms of pond smelt Hypomesus nipponensis in Lake Kasumigaura were estimated using frequency distribution of body length, and the relationship between water temperature. Their growth was studied based on specimens collected by fisheries during the period from June 1992 to February 1998. The growth parameters of von Bertalanffy, Gompertz, and Logistic models and their modified models in which the growth rate changes with one or two cycles per year were calculated by the non-linear weighted least squares method. On the basis of the AIC (Akaike's Information Criterion) values, the modified models in which the growth rate changes with two cycles per year were selected as the best-fitting models for both forms. These formulae represent biological characteristics of the pond smelt in Lake Kasumigaura, i.e. the growth is superior in spring and autumn but inferior in summer and winter. The growth patterns of both forms were similar, but the large form showed a more superior growth rate than the small form from June to July. As for the relationship between the growth and water temperature, until the middle of September the growth was inferior as the cumulative water temperature increased, after which the small form grew to about 82 mm and the large form grew to about 108 mm without any influence from water temperature.