Stock Analyses on the Short-head and Buccaneer Anchovies in the Waters around Taiwan

• Main Authors: Li Lin, 林立
• Other Authors: Tai-Sheng Chiu
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/53506141202155667014

碩士 === 國立臺灣大學 === 生命科學系 === 103 === Bua fisheries are commonly practiced in the coast of Taiwan by artisanal fishermen. Annual abundance of the Bua resources varied, and two congener anchovies are main catch components (e.g., short-head anchovy (Encrasicholina heteroloba) & Buccaneer anchovy (E. punctifer)). Based on the fact that the catch composition varied spatiotemporally, we hypothesize that their recruitment is related with seasonal flow pattern in the southern waters of Taiwan. Nonetheless, these anchovies originated from a single or multiple sources still remain unclear. This study provides important data to improve management plan of the Bua fisheries in achieving their sustainability. To test the hypothesis, I prepared samples that obtained from 2011 to 2013, with 3 geographic nursery grounds of the northeastern (NE), northwestern (NW) and southwestern (SW) Taiwan. Population distinction was quantified by morphological shape differences and degree of molecular segregation. The shape differences reflecting phenotypic responses were analyzed by multivariate statistics. Molecular segregation showing in DNA differences were measured through mitochondrial cytochrome b gene. The results revealed that annual and spatial distinction for short-head and Buccaneer anchovies were insignificant. However, seasonal difference was detected for short-head anchovy, indicating multiple cohort might recruit to the coastal nursery grounds and the recruitment pattern can be explained by the prevailing marine current system in the vicinity of Taiwan. During summer-autumn period, short-head anchovy in the western South China Sea (SCS) migrates north with South China Sea Surface Current (SCSSC) reaching to the coasts of Taiwan. In winter-spring, the east SCS residents migrate to Taiwan due to strengthened northeast monsoon that lessens SCSSC, and promotes Kuroshio Branch Current (KBC) moving waters into Taiwan Strait. Alternating circulation driven by seasonal monsoon results in subpopulation of the short-head anchovy. Nonetheless, Buccaneer anchovy is located in east of Philippines to the Pacific Ocean side, where the geostrophic Kuroshio Current (KC) flows year round with no seasonal segregation. Currently, a unified management plan, established in 2000 is rated reasonable at present for simplicity of regulation, because single stock is found with Buccaneer and Japonicas anchovy. However, climatic changes may have effects on the flow pattern of ocean currents, and subsequently affect the recruitment of short-head anchovy. Therefore, special treatment is also needed when long-term management plan is considered.