This study focus on the specie identification, reproduction biology, age and growth analysis of Trichiurus spp., which from 6 different fishing ports in the southwestern Taiwan.Trichiurus japonicas is a dominant specie and occupy 70.87% of total 8595 samples.Trichiurus nanh aiensis occupy 20.80 %,Trichiurus lepturus occupy 3.21 %. Although Trichiurus nanhaiensis only occupy 20.80% of Trichiurus spp. samples, Trichiurus nanhaiensis is more abundant than Trichiurus japonicas off the shallower fishing ground near the Mituo and Haikou fishing ports. Which suggests Trichiurus nanhaiensis habits in more shallower and costal waters than Trichiurus japonicas .
The VDR and logbook data suggests there was a seasonal variation in the abundance of Trichiurus spp., which was more abundant between Jul.- Sep. and Oct. - Dec. of 2017. Fishing grounds changed with the seasons, mainly distributed at 50-100 m away from Qieding, 100-200 m away from Kaohsiung fishing port 1 and Donggang, and south of Liuqiu Island. We conducted GLMM analysis of resources for the period 1997-2017 and included factors such as year, season, region, and horsepower of fishing vessels. The results show a decline in resources in recent years. Geographically, the area with the lowest amount of resources is D, which is located deeper in the South. In the season change, the second quarter was the lowest amount of resources.
The results of this study can be the scientific evidence for the policy-making and fishery management of Trichiurus spp. fishes.