The population dynamics and parameter of growth and mortality of Sillago sihama in the Minnan-Taiwan fishing grounds

Abstract

The population structure,characters of growth and mortality of Sillago sihama collected by bottom trawl in the southern Taiwan Strait during 2001~2003 were studied, and S.sihama population dynamics discussed using ecological parameters. The results showed that the fork length of S.sihama population ranged from 65 to 237mm, 131~150 mm being predominant,and the mean value was 134.5 mm. The body weight ranged from 5 to 110g, 11~30g being predominant,and the mean value was 26.1g. The age ranged from 0 to 3 years, 1 year being predominant,and the mean value was 0.91 year. The parameters of growth were as follows: L∞=260.89 mm, W∞=153.81g, k=0.6614, t0= -0.6158, tr=0.847 4; the coefficient of total mortality was 2.772 8, the coefficient of natural mortality was 1.300 4 and the coefficient of fishing mortality was 1.472 4, the exploitation rate was 0.531 0.Compared with data of 1992~1993,the population have been miniaturized in size,low-aged, and excessively exploited.The input-output of fishing in this fishing ground was enhanced continuously, the actual annual yield has exceeded their maximum sustainable yield and maximum sustainable fishing efforts for the last 13 years since 1994, and the juvenile fishes were captured heavily,resulted in over-exploitation of both benthic and near bottom fishes including S.sihama. Therefore, it is suggested that protection and management of the fish resources should be intensified, and effective measures should be taken to control the input-output of fishing and the capture size. In the current situation that fishing output and fishing efforts exceed the surplus output of fishery resources,the negative increase strategy must be taken to restore the fishery resources and then achieve sustainable development and sustainable use of fish stocks.