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

正櫻蝦 (Sergia lucens) 為人類可直接利用之少數浮游動物之一，全世界目前僅盛產於台灣西南海域及日本駿河灣。台灣正櫻蝦漁業所使用之網具為中層拖網，但截至目前為止，有關台灣正櫻蝦中層拖網網目選擇性之報告則仍付闕如。本研究係筆者等實際搭乘正櫻蝦作業船出海，調查正櫻蝦與混獲物之種類與數量，並探討拖網內、外袋網網目對正櫻蝦與主要混獲物之選擇性等漁獲性能指標，其結果可作為未來施行資源評估與管理工作時之重要參考依據。實驗結果發現，台灣西南海域正櫻蝦漁業內、外袋網及覆蓋網之漁獲尾數均以正櫻蝦所佔比例最高，分別為66.2%、96.8% 及54.5%。正櫻蝦、白帶魚 (Trichiurus japonicus) 及燈籠魚科 (Diaphus spp.) 等三種主要漁獲物於內袋網之50% 選擇體長分別為3.77、18.62及5.32 cm；正櫻蝦、燈籠魚於外袋網之50% 選擇體長分別為3.38及4.37 cm。內袋網對大型魚蝦類之選擇指距 (SP) 較小型魚蝦類為大，且對魚類之選擇係數 (SF) 較蝦類為大。外袋網對燈籠魚之選擇指距較正櫻蝦者為大，對正櫻蝦及燈籠魚之選擇係數均甚小。

Sergestid shrimp, Sergia lucens, is one of the zooplankton that a few can be utilized as food by human. This species can be found only in the coastal waters of Taiwan and Suruga Bay, Japan. S. lucens is caught by traditional mid water trawl net in Taiwan. However, the mesh selectivity of trawl net in the fishery was not yet studied. This study investigated the mesh selectivity for by-catches and sergestid shrimp. Results showed that the ratio of sergestid shrimp caught in the inner, outer and cover codends were 66.2%, 96.8% and 54.5%, respectively. Analysis on mesh selection using logistic regression indicated that the 50 percentage selection lengths (L₅₀) of the inner codend for sergestid shrimp, hairtail (Trichiurus japonicus) and lantern fish (Diaphus spp.) were equal to 3.77 cm, 18.62 cm and 5.32 cm, respectively. Meanwhile, the (L₅₀) values of the outer codend equaled to 3.38 cm and 4.37 cm, respectively. Selection span of the large fishes in the inner codend was larger than that of small fishes and shrimp. The selection span of Diaphus spp. in the outer codend was larger than that of sergestid shrimp, but their selection factors were similar with each other.