LIFE HISTORY AND SECONDARY PRODUCTION OF THE AMPHILOCHID AMPHIPOD GITANOPSIS JAPONICA HIRAYAMA, 1983, ON A TEMPERATE SANDY SHORE OF KOREA

Abstract

The population ecology and secondary production of the amphilochid amphipod Gitanopsis japonica were studied on a temperate sandy shore in Korea using a sledge net. The life history pattern of G. japonica was annual and iteroparous, with two dominant recruitments in fall and spring. The sex ratio was male-biased. The mean body length (BL) of female G. japonica was significantly larger than that of males, and the mean BL of adults and brood size were greater during spring breeding periods than in the fall. Brood size and egg volume were positively related to the BL of ovigerous females, with egg volume being higher during the fall breeding than in spring. Variation in brood size and egg volume according to variation in the BL of ovigerous females may represent a reproductive strategy to increase the success of reproduction. Annual secondary production (dry weight) was 0.08 g DW m(-2) year(-1), with an annual ratio of production to mean biomass (P/B) of 1.91. Secondary production and P/B ratio of G. japonica were lower than those of amphipods on an intertidal sandy shore, which may have been the result of poor feeding conditions and/or unsuitable temperatures.