Age and Growth of the Largemouth Bass Micropterus salmoides in Lakes Shorenji and Nishinoko, Central Japan

Abstract

Age and growth of the largemouth bass Micropterus salmoides (Pisces: Centrarchidae) were estimated from otoliths taken from samples collected in Lakes Shorenji (Mie Prefecture) and Nishinoko (Shiga Prefecture), water bodies having different physical and biological environments, from October 1991 to March 1993. The otoliths of the fish had narrow opaque and wide transparent zones, with opaque foci. Ring marks (outer margin of opaque zones) were formed on the otoliths once a year from June to August and May to July in Lake Shorenji and Lake Nishinoko specimens, respectively. The number of ring marks indicated approximately the full age of the fish because the marks formed one or two months after the spawning period. The fish from Lake Nishinoko were significantly heavier than those from Lake Shorenji for the same length. The growth curves for length were calculated to be SL_n=341(1-exp(-0.4977(n+0.0697))) (Lake Shorenji) and SL_n=362(1-exp(-0.4576(n+0.0892))) (Lake Nishinoko). Lake Nishinoko largemouth bass grew somewhat more rapidly than those in Lake Shorenji.