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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/25299

Title: 西北太平洋灰鯖鮫之資源評估
Stock assessment of the shortfin mako shark, Isurus oxyrinchus, in the Northwest Pacific
Authors: 張瑞涵;劉光明;金建邦
Contributors: NTOU:Institute of Marine Affairs and Resource Managemen
國立臺灣海洋大學:海洋事務與資源管理研究所
Keywords: 灰鯖鮫;年級群解析;單位加入親魚量模式;隨機生活史階段別模式;總量管制
Isurus oxyrinchus;Virtual population analysis;Spawning stock biomass per recruit;Stochastic stage-based matrix model;Total allowable catch
Date: 2005
Issue Date: 2011-10-20T08:22:11Z
Publisher: 2005年台灣水產學會年會, 屏東, 台灣
Abstract: 本研究以單位加入親魚量以及隨機生活史階段別模式評估西北太平洋灰鯖鲛1990至2004年之資源之狀況及其變動情形,除年級群解析法外,其餘模式皆僅就雌魚資源量之變動進行探討。年級群解析法之結果顯示西北太平洋灰鯖鮫雌魚於7~13歲、雄魚於8~14歲時所承受之漁獲壓力最大,而自1996年開始,雌魚於3~6歲、雄魚於2~7歲之漁獲壓力有明顯升高的趨勢。以固定生活史參數所求得之各年別之SPR介於15.04 %(1996)~38.48 %(1994)之間,僅有1991、1992及1994年達到35%的預警參考點,而將生活史參數加入隨機擾動所求得之SPR趨勢與上述結果相同而值相對較高,二者皆顯示近幾年本資源已過度開發。隨機生活史階段別模式分別以三年及兩年生殖週期之模式模擬現今之資源狀況,亦以2004年實際漁獲尾數取代漁獲死亡係數模擬資源之現況,結果均顯示本資源已經過度利用。不僅如此,分析漁獲資料亦發現本種已有加入量過漁與成長過漁的現象。綜合以上結果均顯示西北太平洋灰鯖鮫已有過漁傾向,本研究建議實施總量管制對本種進行管理,若欲使資源達到平衡,則應減少現今漁獲量的55%,即應限制之總可捕獲量(Total allowable catch;TAC)為265公噸,相當於減少57%之現今漁獲壓力。同時應持續不斷進行監控與修正才能確保本資源之永續利用。
The purpose of this study is to assess the stock status of the shortfin mako shark, Isurus oxyrinchus in the Northwest Pacific from 1990 to 2004 based on two methods namely, virtual population analysis, spawning stock biomass per recruit, yield per recruit and stage-based model. Except for Virtual population analysis, these models were applied on females only. Age-specific fishing mortality estimated from VPA indicated an increase of fishing pressure at age of 3 to 6 year for females and 2 to 7 for males since 1996. Spawning potential ratio (SPR) was estimated to be 15.04 % (1996) to 38.48 % (1994) based on deterministic approach and similar results were found from stochastic simulations. These values were lower than the precautionary reference point of SPR=35% since 1995. The 20-year projection from stochastic stage-based model indicated that the abundance will decrease seriously under current fishing effort. The median size of shortfin mako sharks in the commercial catch data has declined since 1996 suggesting growth overfishing and recruitment overfishing is occurring. The above results indicate the population will be collapse under current fishing pressure. The population will maintain equilibrium for the next 20 years if the total allowable catch (TAC) is set at 265 mt, which equivalent to reduce 57% of current fishing pressure. However, close monitoring and modification of the TAC year by year is a necessary measure to ensure the long-term sustainability of the stock.
URI: http://ntour.ntou.edu.tw/handle/987654321/25299
Appears in Collections:[海洋事務與資源管理研究所] 演講及研討會

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