| Summary: | 碩士 === 國立臺灣海洋大學 === 環境生物與漁業科學學系 === 99 === Escolar (Lepidocybium flavobrunneum) distributes in tropic and temperate waters of three oceans and they are mainly caught by longline fleets. The Taiwanese catch has increased in recent years and escolar has become target species. In this study, the relationships between age and growth are analyzed based age determined using the otolith of escolar sampled from the Atlantic Ocean, Indian Ocean, south Pacific Ocean and the waters off eastern Taiwan. The ranges of fork length of samples are 35-130cm for the south Pacific Ocean, 51-142cm for the Indian Ocean, 60-145cm for the Atlantic Ocean and 40-155cm for the waters off eastern Taiwan. The length-weight relationships are W=1.3×10-3FL1.93 for the south Pacific Ocean, W=4×10-5FL2.68 for the Indian Ocean, W=3×10-5FL2.79 for the Atlantic Ocean and W=2×10-5FL2.90 for the waters off eastern Taiwan. The results of likelihood ratio test indicate the relationships between length and weight are significantly different between oceans.
Monthly marginal increment analysis and percent terminal translucent zone are used to validate the number of the rings on the otolith formed per year and the results reveal that the ring formed about once an year in spring for escolar in three oceans. According to age determination of the transverse sections in three oceans, the age ranged from 1 to 9 yr in the south Pacific Ocean, from 2 to 10 yr in the Indian Ocean; from 2 to 10 yr in the Atlantic Ocean; from 1 to 14 yr in the waters off eastern Taiwan, respectively. In this study, von Bertalanffy growth function growth parameters were also estimated and the results are: L∞=189.3 cm and k=0.096 yr-1 for the south Pacific ocean, L∞=204.7 cm and k=0.099 yr-1 for the Atlantic ocean, L∞=191.1 cm and k=0.097 yr-1 for the Indian ocean, L∞=182.2 cm and k=0.100 yr-1 for the waters off eastern Taiwan. To summarize the growth coefficient estimated in three oceans, escolar growths slowly compared to other fishes. The results of Analysis of Residual Sum of Squares indicate that the growth functions are significantly different between oceans. The result of the difference of the growth coefficient in different oceans might be the different fishing pressures, and the fishing pressure is especially biggest in the waters off eastern Taiwan.
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