Population dynamics of the manila clam Ruditapes philippinarum from Seonjae-do tidal flat, Korea. 1. Growth

초록

Population dynamics of the Manila clam Ruditapes philippinarum were studied in two stations in Seonjae-Do (lat 37°14'N) on the west coast of Korea from September 2008 to February 2010; one station where the annual harvest was consistently carried out but in the other station located at one hundred meter apart across the tidal channel the sand capping was conducted to enhance the productivity. And, the latter station was not exploited previously. Grain size, tidal amplitude, and temperature were measured as ecological factors. The growth and mortality are estimated based on the manila clams collected monthly. As a result, the most important factor influencing their growth was temperature; they grow from March to October but the highest rate in growth rate reaches in June to August when the mean temperature ranges from 20 to 25℃. Growth parameters estimated by the modified von Bertalanffy growth function model showed that the values of L∞ and K were 45.1mm, 53.8mm SL and 0.69yr-1, 0.53yr-1 at each station respectively. The amplitude of seasonal growth oscillation C was 0.97 and 1.00 and the winter point was 0.98 and 0.97 respectively. This result showed clearly the seasonal growth pattern and it slowed down around the end of December. According to the estimated growth coefficient of von Bertalanffy equation, the manila clam population in Seonjae-Do grow until 22mm for a year after the settlement, and they spend one and a half year to be 30mm in shell length. Based on these results, the growth patterns were compared with those of the other regions. In term of sediment types, sand proportions were generally increased at both stations due to the sand capping, but it was more obvious in the station closed to the sand addition point. However, the influence between two stations on the growth of the manila clam was not significantly different.