Seasonal composition characteristics of fishery resources and impact from human exploitation in the Southwest Taiwan Strait

Abstract

This work examined the impact of fishing activities on the marine ecosystem in southwestern Taiwan, an area known for its high productivity and biodiversity due to upwelling and seasonal monsoon-driven currents. Using fishing data from 2014 to 2019, species were classified as pelagic or benthic, and two ecosystem models (summer and winter) were developed using the Ecopath model. Key species in summer included Uroteuthis chinensis and Trichiuridae, while in winter they shifted to Scombridae and Seriola dumerili. The study also analyzed the effects of Taiwanese seine and trawl nets, when catch decreased to 67% and 50%. When fishing was reduced by twofold, The mixed trophic impact (MTI) analysis indicated mostly positive impacts on keystone and dominant species, including a 34% positive impact from Taiwanese seine and a 25% positive impact on Trichiuridae from trawl nets during summer, in contrast to a 51% negative impact on U. chinensis from Taiwanese seine. The relative total impact (RTI) showed that the reduced catch increased the importance of most keystone and dominant species, such as Trichiuridae, but not S. dumerili. Additionally, a network analysis found decreases in total system throughput, biological diversity, and transfer efficiency, suggesting that the fishing intensity in this region may have exceeded the ecosystem's capacity.