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研究報告

更新日期: 2015-02-09
點閱數: 1,221

南太平洋長鰭鮪年齡成長暨印度洋長鰭鮪資源評估研究

年度 2013
計劃名稱 南太平洋長鰭鮪年齡成長暨印度洋長鰭鮪資源評估研究
中文摘要      本計畫之目的包含(1) 南太平洋長鰭鮪年齡成長研究與(2) 印度洋長鰭鮪的資源評估。在南太平洋長鰭鮪年齡成長研究方面,本研究係利用長鰭鮪之第一背鰭硬棘及最後一節尾椎骨,以輪紋判讀法,探討南太平洋長鰭鮪之年齡與成長。2009年6月至2013年2月,由漁業觀察員自南太平洋海域作業之台灣鮪延繩釣漁船收集長鰭鮪硬棘有效樣本共373尾,其中135尾同時採得尾椎骨形質。由於長鰭鮪硬棘核心部位會隨著成長而擴大脈管化之現象,致使早期輪紋逐漸消失而無法判讀。利用135尾同時採得硬棘與尾椎骨之標本,獲得硬棘第一可讀輪徑(R1)與尾椎骨和硬棘間輪數差(ΔCi = Vno - Sno)之相關模式ΔCi = -2.2523+2.9682 R1,並依此進行硬棘輪紋之校正。以373尾標本魚經校正後所得之年齡與尾叉長,以非線性迴歸法估求范氏成長方程式;其成長參數分別為L∞ = 142.9 (cm),k = 0.1371 (1/Yr),t0 = - 1.40 (Yr)。在印度洋長鰭鮪資源評估方面,本研究係應用隨機性年齡群化生產量模式進行資源的評估與風險分析。評估分析時,先選定一組資料(包括歷年來印度洋長鰭鮪的總漁獲量及標準化CPUE的序列資料)及生物參數(最大年齡、各年齡魚的體重、漁具選擇率、成熟率及自然死亡率)作為套適模式分析的基本模式(Base case),再以不同的輸入資料及生物參數建立一系列的的敏感度分析(Sensitivity tests),最後再以一最佳模式(best run)說明資源狀況,並在不同漁獲量軌跡下進行風險分析。評估結果,印度洋長鰭鮪目前的資源狀況:(1)其漁獲量已接近或可能超越MSY的水準;(2)資源耗竭率(B/K)雖還在0.2的水準以上,但已趨近0.4,深值注意;(3)近年來的漁獲死亡率已在最適漁獲死亡率上下浮動;(4)雖然歷年來的成魚生物量均大於達MSY時的成魚生物量而屬合理開發的情況,但近來,尤其是2011年已甚為接近,應注意避免過度開發的情形出現。至於風險評估的結果,也顯示只有在減少20%漁獲量情形下才能維持比目前略低的漁獲死亡率,並且使減少的成魚生物量再趨近於達MSY時的成魚生物量。
英文摘要 The aims of this project include (1)studying on age and growth of albacore in South Pacific and (2) asses the Indian albacore stock. About the studying on age and growth of South Pacific albacore, the 1st dorsal spines and the last caudal vertebrae were used to study the age and growth of South Pacific albacore, by mean of character reading. A total of 373 spines and 135 caudal vertebrae were collected from 373 albacore specimens which were sampled by observers from Taiwanese distant water fishing boats operated in South Pacific, from June/2009 to February/2013. Since the central portion of the spines will become vascularized when fish gets older, the earlier rings will inevitably become obscured. Both spines and vertebrae collected from 135 individuals were used to calibrate the ring counts. From the results, the relationship between first ring of spine (R1) and the difference of ring counts on vertebra and spine (ΔCi = Vno - Sno) was obtained as ΔCi = -2.2523+2.9682 R1. All justified ring counts and fork length data set were then used to estimate the parameters of the von Bertalanffy growth equation by using non-linear regression method, and the results thus obtained were: L∞ = 142.9 (cm); k = 0.1371 (1/Yr); and t0 = - 1.40 (Yr). About the stock assessment, Age Structured Production Model (ASPM) with stochastic recruitment was applied to assess stock status of Indian albacore. For the selection of Base case, yields, indices of abundance and the needed biological parameters are made. A series of model fits related to different assumptions or parameters to examine the sensitivity of the results to these choices were also carried out. The status of Indian albacore resource and risk analysis were assessed by the best run of Base case and sensitivity tests.The results indicated that: (1)the annual yields were closed to or over MSY in recent years; (2)all the estimates of depletion are higher than 0.2, but decreased to the level of 0.4 about in recent years; (3)the fishing mortalities (F) were closed to the mortality at MSY (FMSY) in recent years, even was larger than FMSY  in 2010; (4)though the mature biomass (Bmat  )is still larger than the mature biomass at MSY (B mat MSY) in all the years, the value of Bmat 2011 was very closed to it. And the result of risk analysis indicated that only the yield decreased 20% thus could keep the fishing mortalities lower than F2011 and make the mature biomass (Bmat  ) raised and closed to the mature biomass at MSY (Bmat MSY) in the further 14 years.
計畫編號 102農科-11.1.1-漁-F4(5)
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