農業部-水產試驗所全球資訊網農業部-水產試驗所全球資訊網

自2020年1月至2021年11月止於臺東及澎湖地區採集正鰹生物性樣本進行族群特徵解析。卡方檢定結果顯月別間無顯著差異。利用生殖腺成熟指數及生殖腺成熟度月別變化顯示臺東海域以5 ~ 7月為產卵高峰期。由餌料生物之相對重要性指數分析胃內含物組成，臺東地區正鰹結果顯現最重要之餌料生物以圓鰺( Decapterus spp.) 2409.42為最高，其次為鎖管(Myopsinaspp.) 631.48、飛魚(Exocoetidae spp.) 502.85為第三，澎湖地區正鰹以斑都鰏(Leiognathus bindus) 812.49為最高，其次為日本銀帶鯡(Spratelloides gracilis)388.78、七星燈籠魚(Benthosema pterotum) 91.75為第三。由穩定同位素氮碳分析顯示，臺東正鰹δ¹⁵N平均值為9.87‰；δ¹³C平均值為-17.90‰，營養位階為3.78；澎湖正鰹δ¹⁵N平均值為10.85 ‰；δ¹³C平均值為-18.02 ‰，營養位階為3.88。δ¹⁵N值澎湖高於臺東，δ¹³C值則無明顯差別。利用Bayesian mixing model分析正鰹攝食情況，依結果顯示，鎖管是臺東外海正鰹的主要餌料生物，佔48.4 %，次要餌料生物則為頜圓鰺，佔19.6 %，在澎湖地區，雙帶烏尾鮗是澎湖海域正鰹的主要餌料生物，佔26.0 %，次要餌料生物則為鰏科魚類，佔20.6 %，日本銀帶鯡則為第三重要之餌料生物，佔20.4 %。以粒線體D-loop完整序列進行臺灣沿海正鰹族群分析。結果顯示臺灣正鰹族群數量相當穩定且具有高度流通性。haplotype與NCBI上其他研究之親緣關係相似。所有樣本顯示其基因型具有微弱的分群。本年度標放110尾正鰹(體長範圍介於38.0 ~ 52.0公分(FL))，其中有兩尾為標識放流後14天及62天再捕獲，另外有一尾則在標識放流後440天再捕獲。

Skipjack tuna samples were collected monthly at Shinkang fishing port, Penghu third fishing market and Penghu Suogang fixed net fishing market from January 2020 to November 2021. The result of the chi-square test showed that there was no significant difference in every months. The result shows that the peak period of spawning in the eastern Taiwan waters is May to July. According to the index of relative importance (IRI), the most important prey species in eastern Taiwan waters were Round scad (Decapterus spp.; IRI = 2409.42), followed by Cephalopods ( Myopsina spp.; IRI = 631.48) and Flyingfish (Exocoetidae spp.; IRI= 502.85). In Penghu samples, the most important prey species were Leiognathus bindus (IRI = 812.49), followed by Spratelloides gracilis (IRI = 388.78) and Benthosema pterotum (IRI = 91.75). The δ¹⁵N value was 9.87 ‰, the δ¹³C value was -17.90 ‰ and the trophic position was 3.78 of skipjack tuna in eastern Taiwan waters. The δ¹⁵N value was 10.85 ‰, the δ¹³C value was -18.02 ‰ and the trophic position was 3.88 of skipjack tuna in Penghu waters. It showed that the δ¹⁵N value of Penghu samples was higher than Taitung samples. However, there was no difference between Penghu and Taitung samples in δ¹³C value. Bayesian mixing model results suggested Cephalopods (Myopsina spp.) as the main prey of skipjack tuna in eastern Taiwan waters (48.4 %), followed by Decapterus macarellus (19.6 %). The most important prey from mixing models for skipjack tuna in Penghu waters were Pterocaesio digramma (26.0 %), followed by Leiognathidae spp. (20.6 %) and Spratelloides gracilis (20.4 %). The complete mitochondrial D-loop sequence was used to analyze the skipjack tuna population along the coast of Taiwan. The results showed that the population of skipjack tuna in Taiwan is quite stable and highly circulated. Haplotype was similar to other studies on NCBI. All samples showed that their genotypes have weak clustering. A total of 110 signs were released in the eastern Taiwan waters this year (38.0 ~ 52.0 cm fork length). Two skipjack tuna recaptured in 14 and 62 days. The other one was recaptured in 440 days.