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

本研究以2003-2018年臺東縣新港魚市場所量測之95,714尾鬼頭刀之樣本(雌魚 59,896尾，雄魚35,818尾)及根據2017-2020年新港漁獲資料分析鬼頭刀延繩釣漁獲 組成。漁獲鬼頭刀體長季節及性別方面有明顯差異，組成顯示夏季群之漁獲體長較 大於秋冬季。依體長分析指出7-8月及10-12月可能有兩個加入群進入臺灣東部海域 。漁獲鬼頭刀性比顯示雌魚佔較優勢，總性比為0.62，但隨體長增加雄魚比例越高 ，因此雄魚體長較大於雌魚。體長分布變動顯示，由於漁撈壓力可能導致目前臺灣 東部海域鬼頭刀漁獲體型分布均有小型化之趨勢。鬼頭刀延繩釣漁獲鬼頭刀佔 85.1%，混獲率僅14.9%，月別混獲率介於8.9-23.9%之間。當鬼頭刀盛漁期期間3- 5月及10-12月期間混獲率分別為14.9-16.6%和8.9-13.2%，表示鬼頭刀盛漁期時混獲 率較其他月別低。鬼頭刀延繩釣漁船各月別作業海域於新港外海附近，而冬季則有 逐漸北移至花蓮海域作業。利用彈脫式衛星標識器(PSAT)標識4尾鬼頭刀(尾叉長 94–102 公分)。共記錄5-31的行為資料(Σ= 69天)，從標放位置到彈脫位置的直線 距離為63-204 公里。最可能的移動路徑，結果顯示，標識之鬼頭刀主要向北移動。 垂直移動深度從海表面至94 公尺深，棲息環境溫度範圍為17.8-23°C。根據群聚分 析顯示不同之混合層有所不同，因此各海域之鬼頭刀棲息溫度有所差異。本研究的 初步結果為支持當地重要漁業提供鬼頭刀延繩釣的漁場動態及移動行為，這些結果 將有助於資源評估所需之重要資訊，使鬼頭刀能達到永續利用之目標。

In this study, length-frequency and sex ratio (proportion of females) of dolphinfish were analyzed based on 95,714 (59,896 were females and 35,818 were males) samples measured in Shingkang fish market during 2003 to 2020, and catch compositions of dolphinfish longline fishery were also explored based on the catch records collected from Shingkang fish market during 2017 to 2020. There were significant differences in the length and sex ratio of the catches in the two seasons, with the length of the catch in summer being significantly greater than that in winter. However, there are two recruitment to eastern waters of Taiwan from July to August and October to December. The sex ratio shows that females are dominant, with a total ratio of 0.62. The proportion of male becomes higher than females when body length increased. The results of this study indicated that fishing exploitation might have led to the decreases in the body size in recent years. The 85.1% of the catch dolphinfish for dolphinfish longline, the by-catch are only 14.9%, and the monthly by-catch shows that the between 8.9-23.9%, which during the fishing season of dolphinfish the by-catch from March to May and October to December were 14.9-16.6% and 8.9-13.2% respectively, indicating that the by-catch during the fishing season of dolphinfish was lower than other months. The dolphinfish longline vessel option area distribution off Singang waters of months, but gradually move north to Hualien coastal waters in winter.  Pop-up satellite archival tags (PSATs) were deployed on four dolphinfish (94–102 cm fork length), caught using set-nets in the northern East China Sea. Tagged dolphinfish retained PSATs for 5–31 days-at-liberty (total 69 days) and linear dispersion from deployment to pop-up locations ranged from 63 to 204 km. According to most probable tracks, tagged fish made primarily northward movements. Tagged fish reached depths of ~94 m and experienced ambient temperatures from 17.8 to 23°C. The cluster analysis suggests a clinal trend of distinct thermal clusters with limited mixing among locations. Our preliminary results provide dymainc of dolphinfish longline fishing ground and movement patterns of dolphinfish in a location that supports important fisheries. This information will be useful for management to develop stock assessments which support the sustainable use of this species.