[AHW33-P01] The possible influence of climate variability and fishing activity on the annual fishing conditions of Grey mullet (Mugil cephalus L.) in the Taiwan Strait
Keywords:Grey mullet, Climate change, Pacific Decadal Oscillation, Cohort analysis, Wavelet analysis
The long-term unique long-term (1967–2009) records of catch per unit effort (CPUE) of Grey mullet in the TS was further used to investigate the influences of multi-timescale climatic indices on the annual catch of grey mullet. The CPUE of Grey mullet showed fairly good correspondence with the annual PDO index (R2=0.82, p<0.01). The PDO may play a role in affecting the migration of grey mullet, but increases in SSTs may be a main reason for the decreased catches after 1980.
This study is to estimate exploitable biomass and recruitment of grey mullet stock in the Taiwan Strait. Cohort analysis was employed to estimate population number and the instantaneous rate of fishing mortality (F) by age for 1958-2004. The population number of grey mullet in the Taiwan Strait decreased from late 1960s to early 1970s due to the high instantaneous rates of fishing mortality in 1960s. Since 1986, annual catches sharply dropped and continuously remained at a very low level these years despite of the high fishing intensity, which indicates that overfishing has existed since 1960s. The population number of age group over age 4 has decreased since 1986 and reduced to be 20 thousand individuals in 2004, which is only 1/100 of the maximum level of 2 million individuals in 1981. It seems that the grey mullet stock has lost the reproductive ability due to the severe recruitment overfishing.