FISHERIES RESEARCH INSTITUTE,MOA,TAIWAN

This study focused on the species populations in the northwest and southeast waters of Penghu based on bottom trawl fishery hauls. During the study period, 164,502 fishes belonging to 103 families and 273 species were caught. The most abundant fish in the northwest waters was Leiognathus rivulatus. The most abundant fish in the southeast waters was Gazza minuta. Monthly variations in the numbers of species ranged between 23 and 99. Monthly variations in the numbers of individual fish ranged between 1,364 and 31,919. Monthly variations in catches per unit effort (CPUE, kg/hr) ranged between 11.5 and 63.5. We analyzed monthly catches, which showed that the richness index ranged between 2.9 and 11.3, evenness ranged between 0.1 and 0.7, and the diversity index ranged between 0.4 and 3.0. The data show that the diversity index was greater than 1 for almost every month, indicating that the biodiversity of the station selected for this study was high. The dominant species identified in the southeast waters were Leiognathidae, which have low economic value, whereas the dominant species in the northwest waters differed significantly each month. Furthermore, we analyze five economical fishes, including Upeneus japonicas, Trichiurus japanicus, Psenopsis anomala, Evynnis cardinalis, and Polydactylus sextarius. The average fish total lengths of Upeneus japonicas, Trichiurus japonicus, and Psenopsis anomala in this study indicated that these fish had achieved mature lengths. The total catch biomass of the five economical fishes was 702.8 kg, accounting for 34.4% of the total catch biomass. Although bottom trawl fishery has a high catch efficiency, large numbers of bycatch species were observed. If bottom trawl fishing gear can be improved to reduce the rate of bycatch species, the sustainable use of fishery resources can be maintained.