臺灣周邊水域異葉公鯷與刺公鯷之系群分析

Stock Analyses on the Short-head and Buccaneer Anchovies in the Waters around Taiwan

林立(Li Lin)

指導教授 ： 丘臺生

國立臺灣大學/生命科學院/生命科學系/碩士(2015年)

https://doi.org/10.6342/NTU.2015.01768

摘要

魩鱙漁業為臺灣周邊水域重要小型漁業，其捕獲物種主要由日本鯷、異葉公鯷與刺公鯷三種鯷科仔稚魚所組成。由2002年到2012年的豐度組成得知此兩種仔稚魚豐度存在年間及季節間變異。藉由漁獲組成之時間別及海域別間差異分析，可推測異葉公鯷與刺公鯷乘著台灣南面洋流添入沿岸漁場，且此兩種魚洄游至產卵場時間及深度相當；然而是否源自南方單一系群或多個系群仍有待釐清。本研究主旨為分別探討此二物種之仔稚魚如何匯入臺灣海域，以完成其生活史之成育階段，並且定義其單位系群。究明其南方來源有助漁業管理之實務及理想性，可達成沿岸魩鱙魚獲資源永續利用之目標。
本分析所需樣本得自2010至2013，空間區分為三個分立成育場，分別為臺灣東北、西北及西南海區。年別樣本將反應添入年級群強度，並分為春季與秋季兩個季節群。族群性狀特徵以外形與分子差異分別定量。外形區分由族群多變數形態分析檢定，而分子差異由粒線體中胞色素b為族群標記，由完整三因子變方分析結果顯示系群關係。
統計分析於外形性狀判別中，異葉公鯷樣本呈現春秋兩季節獨立分群，此結果於基因序列分析再次被驗證，可得知異葉公鯷仔稚魚源自兩個獨立母魚群體，並且於不同季節時各自匯入沿岸漁場；統計結果顯示刺公鯷則無顯著分群現象，應為單一系群。此分群現象與臺灣周遭洋流之季節交替系統相對應，夏季時棲息於南海西岸的異葉公鯷藉由南海海流到達台灣成育場，而冬季時東北季風增強，中國沿岸流順勢強度提升，導致南海暖流方向轉為順時針，此時南海東岸的異葉公鯷乘著黑潮支流得以到達台灣，因此可見春秋兩分立季節群；相反地，匯入台灣的刺公鯷主要源自菲律賓群島東岸之太平洋，整年由黑潮遷移至台灣繁殖，故並無系群分群現象。
目前臺灣地區全區適用之魩鱙管理，基於刺公鯷與日本鯷皆屬單一系群，沿岸魩鱙漁業以單一系群管理之規範應屬合理，然而多系群的異業公鯷受台灣周遭表層流影響甚巨，受氣候變遷(例如聖嬰現象)改變洋流系統，將連動影響異葉公鯷添入漁場的相對豐度，因此在長期管理上應納入氣候變遷因子，以達魩鱙漁業永續經營之目標。

關鍵字

漁業資源 ； 異葉公鯷 ； 刺公鯷 ； 細胞色素b

並列摘要

Bua fisheries are commonly practiced in the coast of Taiwan by artisanal fishermen. Annual abundance of the Bua resources varied, and two congener anchovies are main catch components (e.g., short-head anchovy (Encrasicholina heteroloba) & Buccaneer anchovy (E. punctifer)). Based on the fact that the catch composition varied spatiotemporally, we hypothesize that their recruitment is related with seasonal flow pattern in the southern waters of Taiwan. Nonetheless, these anchovies originated from a single or multiple sources still remain unclear. This study provides important data to improve management plan of the Bua fisheries in achieving their sustainability.
To test the hypothesis, I prepared samples that obtained from 2011 to 2013, with 3 geographic nursery grounds of the northeastern (NE), northwestern (NW) and southwestern (SW) Taiwan. Population distinction was quantified by morphological shape differences and degree of molecular segregation. The shape differences reflecting phenotypic responses were analyzed by multivariate statistics. Molecular segregation showing in DNA differences were measured through mitochondrial cytochrome b gene.
The results revealed that annual and spatial distinction for short-head and Buccaneer anchovies were insignificant. However, seasonal difference was detected for short-head anchovy, indicating multiple cohort might recruit to the coastal nursery grounds and the recruitment pattern can be explained by the prevailing marine current system in the vicinity of Taiwan. During summer-autumn period, short-head anchovy in the western South China Sea (SCS) migrates north with South China Sea Surface Current (SCSSC) reaching to the coasts of Taiwan. In winter-spring, the east SCS residents migrate to Taiwan due to strengthened northeast monsoon that lessens SCSSC, and promotes Kuroshio Branch Current (KBC) moving waters into Taiwan Strait. Alternating circulation driven by seasonal monsoon results in subpopulation of the short-head anchovy. Nonetheless, Buccaneer anchovy is located in east of Philippines to the Pacific Ocean side, where the geostrophic Kuroshio Current (KC) flows year round with no seasonal segregation.
Currently, a unified management plan, established in 2000 is rated reasonable at present for simplicity of regulation, because single stock is found with Buccaneer and Japonicas anchovy. However, climatic changes may have effects on the flow pattern of ocean currents, and subsequently affect the recruitment of short-head anchovy. Therefore, special treatment is also needed when long-term management plan is considered.

並列關鍵字

Fishery resources ； Encrasicholina heteroloba ； E. punctifer ； Cytochrome b

參考文獻

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