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研究報告

更新日期: 2015-02-09
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三大洋溫帶鮪類生物暨資源研究

年度 2013
計劃名稱 三大洋溫帶鮪類生物暨資源研究
中文摘要 「三大洋溫帶鮪類生物暨資源研究」之中文摘要: 一、「南大西洋長鰭鮪資源評估研究」        本研究將比較研析臺灣南大西洋鮪釣漁船作業所填報之logbook與觀察員資料。並將1982-2011年間臺灣南大西洋鮪釣漁船作業所填報之長鰭鮪漁獲體長資料,進行漁獲 體長年齡轉換,以估算長鰭鮪漁獲之年齡結構,進行資源補充量推估。再以GLM標準化1967-2011年我國大西洋長鰭鲔資源豐度指標(CPUE),分析南大西洋長鰭鮪漁獲變動與海洋環境變化之關聯。最後以年齡結構餘量模式,探討南大西洋長鰭鮪之資源現況、漁業資源最適利用策略並進行風險評估,作為資源管理之參考。計畫執行後,可獲得之俱體效益為對南大西洋長鰭鮪資源之合理永續利用提供重要之參考依據,並確保我國利用大西洋長鯺鮪資源之權益。  結果顯示:(1)由歷年之體長頻度與年齡頻度分布而言,將臺灣鮪釣漁船作業漁區分布分為3 subregion ,較北之subregion1與2體長年齡都較大,而南邊的subregion 3較小,且於subregion 1發現其中似乎可得循環現象,或許存在族群生物活動跡象(如產卵或遷徙)。(2)環境因子影響方面:溫度與對應該時空之平均體重而言有最大相關性,其相關係數達0.688,顯示高度相關,同樣的情形亦在葉綠素與該時空之長鰭鮪捕獲數目出現,而海水表層之鹽度與長鰭鮪資源量較無關係。(3)由1967年-20112之標準化CPUE Trend所示南大西洋長鰭鮪資源自1967年起呈現緩步下降趨勢,1990年代後有緩慢回升,但在1997年又緩慢下降至2003年達到最低水平,但自2003 年之後CPUE trend 之趨勢有緩步上升持平的情形,且GLM最強影響因子為漁區(4)ASPM模式顯示資源量每年24000噸為最佳管理標準,以2011年產卵親魚量(Spawning stock biomass, SSB2011) 為基礎,預估有50%風險水準5年內資源量可回復至MSY水準甚至更好的狀態。 二、「北大西洋長鰭鮪資源評估研究」        本計畫主要重點為:(1) 利用不同的方法區分標的魚種為長鰭鮪與標的魚種非長鰭鮪之我國遠洋鮪釣漁業北大西洋長鰭鲔漁獲統計資料,並利用GLM等模式方法,標準化北大西洋長鰭鮪資源豐度指標(CPUE),以解析其年間變動趨勢;(2) 利用體長年齡成長關係式,轉換我國北大西洋長鰭鲔漁獲體長組成性狀為年齡組成; (3) 利用年齡結構化餘量模式(ASPM),評估北大西洋長鰭鲔之資源狀態.  研究結果如下:(1)檢視台灣漁船在北大西洋作業之漁撈日誌,漁船投放鈎數之資料顯示,鈎數別努力量分布呈現雙峰的型式,分別在9-10鈎及16-17鈎出現最大的努力量,唯每匡鈎數為6-13鈎時,長鰭鮪有明顯較大的漁獲比率;(2) 使用1999至2012年間作業日誌資料,依(1)之結果將台灣延繩釣中每筐投放鈎數小於16者,視其標的漁獲為長鰭鮪,且使用於本研究中,標準化CPUE每年持續增加至2004年,此後,它仍然是相對穩定的(2005-2009年),然後2010-2011年間逐步增加;此結果與利用TASK II資料,經不同模式較正後,顯示 2005年至今,北大西洋長鰭鮪資源豐度指標持續保持穩定之結果稍有不同;(3) 台灣在北大西洋長鰭鮪主要漁獲年齡從早期至現今有變大之趨勢,1981~1997主要漁獲年齡在5-8齡、1999~2006約在6-10齡,而2007年之後則約在7-11齡;32區的漁獲年齡大都大於4,而31區大都大於3; (4) ASPM估計近五年平均之MSY為 34500噸、BCUR /BMSY =0.952及FCUR/FMSY 0.61,亦即表示,北大西洋長鰭鮪目前資源處於過漁狀態(overfished, BCUR /BMSY <1), 但近幾年(2008年後)此資源未處於過漁中(overfishing, FCUR/FMSY <1)。 三、「北太平洋長鰭鮪資源研究」        本研究以作業模式及漁獲結果將北太平洋作業之臺灣鮪延繩釣漁業區分為兩種漁業,以分群後的資料進一步分析長鰭鮪長期變動趨勢。並依據1995~2011年北太平洋捕獲漁獲組成及漁業資料之分布特性進行漁區劃分,各漁區特性包含漁業(漁獲組成、努力量)及生物(體長)特性有明顯差異。分區結果用為GLM標準化CPUE參數之一,合理反映我國北太平洋長鰭鮪漁業訊息。標準化CPUE trend在2000年震盪幅度並不明顯,長期趨勢都維持在小幅度的變動。長鰭鮪在2003年後紀錄體長增大,又以北緯25度以南體長較北側大、非以長鰭鮪為目標的漁獲體長較以長鰭鮪為目標的漁獲大。年齡結構在1995~2002年以2~4歲魚為主,2003~2011年以4~6歲魚為主。以我國北太平洋鮪延繩釣漁業統計資料分析長鰭鮪移動模式的初步成果,5歲(含)以下中幼齡長鰭鮪的每月CPUE重心均在北緯25度以北,6歲(含)以上長鰭鮪CPUE重心在6、7月南移至熱帶、亞熱帶海域,8歲(含)以上的CPUE重心在9~3月似乎有以逆時針方向洄游的情形。本年度分別於3月19~26日於中國上海及11月5~12日於日本清水參加ISC長鰭鮪工作小組會議,會議中參與檢視過去訂定的主要研究工作及討論2014年資源評估相關研究,提出我國北太平洋長鰭鮪研究結果。會議中提出的報告有(1)Development of Taiwanese albacore-targeting longline fisheries in the North Pacific Ocean, 1995-2010.(2)Taiwanese albacore-targeting longline fisheries in the North Pacific Ocean, 1995-2011. 四、「南太平洋長鰭鮪資源研究」       本計畫為科技保密計畫,故不引入相關資訊,請另參照細部計畫期末報告紙本。 五、「南太平洋長鰭鮪年齡成長暨印度洋長鰭鮪資源評估研究」            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 Abstract of "Fisheries biological traits and stock assessment on temperate tuna resources in the three Oceans": 1. "Assessment on the Stock Conditions of Albacore Resource in the South Atlantic Ocean." :       This study will analyze the fishing logbook and observer data of Taiwanese tuna fishing vessels in South Atlantic Ocean. First transfer 1982-2001 Catch-at-size data into Catch-at-age to estimate age-structure and evaluate the recruitment of South Atlantic Albacore. And then use GLM to standardize CPUE trend, analyze the relation between Albacore catch and the marine environmental conditions. Finally, use Age Structured Production Model (ASPM) to assess the current stock status, find the optimal fishing strategy and implement risk analysis of South Atlantic albacore stock to provide crucial information of fishery management need. The results of this project will offer effective benefits for sustainably utilizing the South Atlantic albacore resources, ensuring the rights and interests of Taiwanese South Atlantic albacore fishery. The results obtained as follows: (1) Based on the dominancy of albacore in their different oceanic habitats, summarized and pictorically shown their size distribution characters respectively, there are 3 subregions in the South Atlantic ocean: in which big-size in the subregion 1&2,and small ones in the 3. And we found out there have been a circular fluctuations occurred in subregion 1 might imply some biological phenomena had arisen. (2) The most significantly related to sea surface temperature is average weights of albacore catch with a correlation coefficient 0.688,and to chlorophyll is the numbers of albacore catch with a correlation coefficient 0.707,however there is no significant relationship between salinity and all albacore catch factors.(3) According to the standardized CPUE trend ,we see a continuous decline from the beginning of Taiwanes longline fishery to 90s, then increase till the mid 90s, and leveled off since 2003 up to 2011.And factor “subregion” played the most important role in explanation of the model.(4) Evaluated by ASPM , with a the criteria 24,000mt as a constant TAC(Total allowable catch), we can assure that there appears a risk of smaller than 50% chance that the prospecting SSB/SSB2011 will reach the value always greater than 1 in-5years. 2. "Assessment on the Stock Conditions of Albacore Resource in the North Atlantic Ocean" :       The main tasks of this project are : (1) to use various methods to distinguish the fishing data targeted at albacore from targeted nonealbacore species and to use GLM model to standardize the Taiwanese distant long line fisheries effort statistics in the north Atlantic to obtain more correct CPUE trend; (2) to convert, based on age and growth equation, on Taiwanese CAS (catch at size) into CAA (catch in age) of Taiwanese albacore harvested in the North Atlantic; (3) to use ASPM to assess the albacore resource condition.   The results indicated (1) the effort distribution for hook per basket of Taiwanese logbook data indicated two modes, and the most effort was separately found in 9-10 and 16-17 hooks; the bigger catch rate of albacore was obtained by 6-13 hooks; (2) to remove the effect of target species, the Taiwanese long-line logbook data identified as albacore targeting (less than 16 hooks per basket) from 1999 to 2012 were used here and shown that the yearly-standardized CPUE continuously increased up to 2004, thereafter, it remained relative stable (2005-2009), and then further increased during 2010-2011; (3) the main age of Taiwanese catch of albacore got bigger from 1981 to 2010; the main age of Taiwanese catch was 5-8 from 1981 to 1997, the one was 6-10 from 1999 to 2006, and the one was 7-11 from 2007 to 2010 . In general, albacore caught in area 32 is bigger than caught from area 31. The majority of Taiwanese catch of albacore is greater than age 3 in area 31 and is greater than age 4 in area 32; (4) the averages of last five year results obtained from ASPM for MSY,、BCUR /BMSY and FCUR/FMSY are 34500 ton, 0.952 and 0.61, respectively, and we agree the conclusion for Stock Conditions of Albacore Resource in the North Atlantic Ocean from ICCAT (2013) that the stock is slightly overfished, but is no longer undergoing overfishing. 3. "Study on the stock conditions of albacore resource in the North Pacific Ocean" :       In order to gain a better knowledge of abundance index for the north Pacific albacore exploited by Taiwanese longliners, the generalized linear model (GLM) was applied to the daily logbook records of albacore-targeting fleets, which were defined based on their fishing activities and resultant catch compositions. In the GLM analyses, several sub-area segregations were adopted, and results showed that 2 sub-areas divided by 25oN Lat. can explain the highest proportion of variance either for the model or for the area factor itself. The GLM results revealed that the standardized CPUE fluctuated within a rather small range, suggesting that the north Pacific albacore population is currently under a reasonable exploitation, particularly since 2001.In this study, we also investigate the age compositions of north Pacific albacore based on length frequency data, given by OFDC, and growth equation reported by Wells et al. (2013). In the period 1995-2002, the albacore catch of Taiwanese longliners were mainly contributed by fish of age 2-4. Since 2003, significant proportion of the albacore catch was comprised of age 4-6 groups. Seasonal differences in the geographical distributions between age groups were observed. The CPUE gravity centers of albacore at age 5 and younger remained in the waters north of 25o N Lat. throughout the year, while those of fish older than 5 years tended to move down to the subtropical and tropical waters in June and July. Based on the monthly distribution of CPUE gravity center, those of fish older than 7 years likely move counter clockwise in the central north Pacific Ocean in the period of September-March. 4. "Studies on the resource condition of south Pacific albacore" :      本計畫為科技保密計畫,故不引入相關資訊,請另參照細部計畫期末報告紙本。 5. "Age and growth study of South Pacific albacore and stock assessment of albacore in the Indian Ocean" :      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(Z)
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