Ecological Risk Assessment of Large Migratory Species in the Western and Central Pacific Ocean

• Main Authors: Po-Yuan Chen, 陳柏沅
• Other Authors: Chi-Lu Sun
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/67093781018789397112

碩士 === 國立臺灣大學 === 海洋研究所 === 102 === Productivity and susceptibility analysis (PSA) was used to assess the ecological risk of large migratory species in the western and central Pacific Ocean (WCPO), including albacore, bigeye tuna, yellowfin tuna, Pacific bluefin tuna, longtail tuna, skipjack tuna, swordfish, striped marlin, blue marlin, black marlin, sailfish, common dolphinfish and wahoo. Information from tuna longline (LL), tuna purse seine (PS) and pole and line (PL) fisheries was also used in the analysis. The risk for swordfish, striped marlin, and albacore was assessed by putative stock boundaries (northern and southern) in the WCPO. The productivity index represents the capacity of the stock to recover and was estimated based on biological parameters of the species, including von Bertalanffy growth coef&;#64257;cient, natural mortality (M), maximum age, trophic level, age at 50% maturity and annual fecundity. Six attributes for susceptibility were calculated including (1) areal overlap of fish distribution and fisheries, (2) vertical overlap (i.e., fish depth distribution and fisheries), (3) ratio of fishing mortality (F) to M, (4) fish price, (5) schooling behavior and (6) annual catch trends that represented factors to measure the potential impact of fishing on stocks. Vulnerability for each stock was calculated based on the ranking of the productivity and susceptibility attributes, which was then used to evaluate the ecological risk of the species. Results showed that the ecological risk for Pacific bluefin tuna, black marlin, bigeye tuna and the northern stock of striped marlin were high, suggesting a critical need for detailed monitoring that would, in turn, allow for stock assessments, with special reference for black marlin that to date, has not been assessed. For species identified with medium risk (such as the southern stock of swordfish, blue marlin, both stocks of albacore, longtail tuna, sailfish, the southern stock of striped marlin and yellowfin tuna), data for stock assessments should be collected continuously. The fishery using resources with lower risk (such as the northern stock of swordfish, skipjack tuna, common dolphinfish and wahoo), should be monitored closely. As indicated by removing one variable each time in the sensitivity analysis, the impacts of schooling behavior and maximum age were highly significant in the model, but were relatively minor for trophic level and fish price. The data quality analysis indentified gaps in knowledge and suggests that further studies are warranted for longtail tuna, common dolphinfish and wahoo to obtain biological parameters, and that fishery information and data should also be collected for longtail tuna.