Estimation of biological reference points for North Pacific bluefin Tuna

• Main Authors: Huang, Hsiang-Wen, 黃向文
• Other Authors: Hsu Chien-Chung
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/42459111898481486970

博士 === 國立臺灣大學 === 海洋研究所 === 91 === The annual catch of North Pacific bluefin tuna fluctuated between 20 and 30 thousands metric tons since 1952. In Taiwan, the catch of small-scale longline fisheries increased in recent years. It was difficult to standardize the fishing efforts since it was a multi-gears fishery. Meanwhile, we could not get enough fisheries data since we was not the major fishing countries. The object of this study is to estimate the biological reference points for conservation of North Pacific bluefin tuna under a data-limited situation. The aim of this research, which bridge those models included yield per recruit models and spawner-recruit models, is to estimate the equilibrium production curve of North Pacific bluefin tuna. Beverton and Holt model (1957) and age-structured model were used to estimate the yield per recruit and spawner per recruit. Some shape parameters were used to estimate the Ricker (1954) and Beverton and Holt (1957) spawner-recruit models. Those biological reference points such as maximum sustainable yield (MSY), fishing mortality for MSY (FMSY), F0.1 and Fmax were estimated from these models. We also analyzed the management-related quantities in relative terms (e.g. MSY/So). Using the Beverton and Holt and age-structured yield per recruit models, we found that the F0.1 and Fmax were between 0.100 to 0.187 and 0.142 and 0.336, respectively. In the case of Ricker Spawner-recruit models, the production curves were symmetric as functions of F. MSY ranged from 9,483 to 24,563 MT, and the values were about 6.3% to 16.4% of So. FMSY ranged from 0.103 to 0.322. The exploitation rate ranged from 29.2% to 56.3%. The fishing mortality at collapse (Fcrash) fluctuated between 0.199 and 0.629, and they were about 1.932 to 1.953 times of FMSY. In the case of Beverton and Holt Spawner-recruit models; the production curves were asymmetric as functions of F. MSY ranged from 5,676 to 11,589 MT, and the values were around 3.8% to 7.7% of So. FMSY ranged from 0.075-0.249. The exploitation rate ranged from 23.1% to 49.9%. The fishing mortality at collapse (Fcrash) fluctuated between 0.180 and 1.025, and they were about 2.400 to 4.116 times of FMSY. It showed that MSY and FMSY would be higher in Ricker models than in Beverton and Holt model. And the Fcrash of Beverton and Holt model was higher because of the stability of Beverton and Holt model. The MSY and other biological reference points were estimated only by growth parameters and unexploited spawning stock biomass. The recommended maximum sustainable yield ranged from 5,676 to 24,563 metric tons. The average annual catch for the last 10 years was 17,937 MT. It seemed the resource was under reasonable utilization in the status quo. But it noticed that the catch of these two years were increased. Since the parameters used in this models were limited, it is important to clarify the stock-recruit relationship and related biological parameters for the sensitivity of uncertainty.