A. Spawning grounds and reproductive biology of economic demersal fishesThe reproductive biology of Psenopsis anomala, and Saurida spp. were examined from samples which were collected by cooperative artisanal bottom trawler every week in southwestern Taiwan. The date, time, GPS positions, and speed of each trawler was recorded by Vessel Monitoring System developed by the Coastal and Offshore Resources Research Center, Fisheries Research Institute. The trails of trawling drawn on Geographical Information Software, and the matured stages of each landing were investigated for possible spawning grounds. The female P. anomala with matured ovaries were lasted from May to October during this study. Most female with matured ovaries were from off Zihguan, and off Tunkang the females with matured ovaries were only collected in June. Two species of saurids, Saurida tumbil and Saurida undosquamis, were the landings of Saurida spp. in southwestern Taiwan. Saurida tumbil which is larger than Saurida undosquamis habitats the waters shallower than 100 m depth, and the female with matured ovaries were found from July to September. Most matured female of Saurida tumbil were trawled off southwestern Tunkang. Saurida undosquamis habitats mainly between 100 and 200 m depths, and the female with matured ovaries were found only in September. During early October, the spawning of female Saurida undosquamis was completed in the shallower waters off Tunkang.B. Mesh selectivity of trawl netIn selectivity investigation of trawl mesh sizes, there were 2 operations with meshes of model A (1.5, 6.0, and 8.6 cm) for a cruise in February and 2 operations with meshes of model B (1.5, 6.0, and 7.5 cm) for a cruise in April. Total catch of 131.6 kg for 25,325 individuals and 52.9 kg for 12,145 individuals were collected in Feb. and Apr. cruises, respectively, and most were fish. Average operating time was 1.5 hours, and mean capture per unit effort (CPUE) was 30.75 kg in each operation. Fish were 33.60% for individuals and 77.39% for weight in catch contents analysis, and others were crustaceans and cephalopods. In additional, main commercial fish species were Psenopsis anomala and Trichiurus lepturus.More than 50% of total catch were commercial species. Retained rates were 69.43% and 91.82% for 6.0 cm mesh size in 2 cruises, respectively, indicated that trawls with this mesh size maintain commercial efficiency and simultaneously release small size of valueless catches.C. Mesh regulations of bottom trawl for the protection of economic immaturefishesThe present research adopts with the application of the sequential mesh regulations on bottom trawl to study how to protect economic immature fishes. The experimental design includes first the determination of the relationships of fish size and the price per weight (PPW) of the economic demersal fishes sold as the one-hundred Dollars-a-plate manner in Tunkang and Zihguan fish markets in the southwestern coast of Taiwan. The obtained results were used to yield the catch of smaller size fishes and the lower PPW for regulating the economic immature fishes. The three kinds of regulated fish size were defined as the smallest surveyed size, smallest economic size, and smallest matured size. These regulated fish size were used as the body lengths of 50% selection (L50) to calculate the regulating mesh size. This study presents that four steps are needed for the sequential mesh regulations of bottom trawl in the southwestern Taiwan. The first step is to regulate the mesh size between 35 and 45 mm for banning bottom trawler to catch fishes smaller than the smallest surveyed fish size. The objective of first step is to reduce the bycatch without affecting the landings of economic immature fishes sold in the fish market. The second step is to regulate the mesh size between 50 and 60 mm for banning bottom trawler catch fishes smaller than the smallest economic fish size, and to reduce the catch of smaller size fishes and the lower PPW of economic immature fishes. The third step is to regulate the mesh size between 65 and 70 mm for banning bottom trawler to catch fishes smaller than the smallest matured fish size. This is also to reduce the catch of economic immature fishes, and to increase the recruitment. The fourth step is to regulate the mesh size between 70 and 82 mm for banning bottom trawler catching the lower PPW of economic fishes that is not large enough to reach their optimal PPW. The present research provides important data results for regulating the mesh size of bottom trawler operation for the achievement of sustainable coastal fishery in Taiwan.D. Sergestid shrimp fishery This report included the analysis on the fishing condition based on the catch statistics collected from 16 sampling vessels and fish market during the period from November 2007 to May 2008. Meanwhile, the analysis on the biological characters of sergestid shrimp based on the sampling data was conducted during the period from November 2007 to October 2008. The average fishing time was 1.76 hours with a CPUE of 64.71 kg per net haul. The species composition included sergestid shrimp (58.09%), myctophid fishes (26.23%), and the other fishes (15.68%). The annual landing of sergestid shrimp in the fish market was 1440.07 tonnage with a value of 39,975 ten thousand N.T. dollars. The productivity in the coastal area off Fan-Shan was higher than the coastal area off Tung-Kang. The monthly ratio of female shrimp was between 42.94% and 81.28% with a peak in March. The length-weight regression equations of the female and male shrimp were calculated as BW=9x10-6BL2.9060，r=0.897 for female, and BW=2x10-5BL2.7433，r=0.877 for male.