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

為減輕宜蘭灣海域中小型底拖網漁船對未成熟魚體之混獲比率，於2004年11月2日至同年12月16日間，租用大溪籍拖網漁船「新遠發63號」(總噸位52.10噸，800匹馬力)，利用覆蓋網方法進行網目選擇性試驗。其中，囊網之網目為7 cm，覆蓋網之網目則為3 cm。設定之線性生物量為大於或等於0.5及Logistic regression model之顯著水準為5% 進行篩選，共計求出14種魚類及6種蝦之體長選擇範圍。結果顯示選擇範圍依各魚種之體寬與全長之比率而異。該種網目規格可讓67.55% 未達最小生物成熟體長之真鰺 (Trachurus japonicus) 魚體由目大7 cm之囊網逃脫，而刺鯧 (Psenopsis anomala)、大眼鯛 (Priacanthus macracanthus)、白帶魚 (Trichurus lepturus)、黑魚或 (Atrobucca nibe)、花斑蛇鯔 (Saurida undosquamis) 等幼魚之逃逸率則分別為38.20%、100.00%、54.60%、35.71% 及54.43%，顯示對於未達最小生物成熟體長之幼魚有顯著之保護作用。

In order to reduce the catch rate of immature fish caught by baby bottom trawler in Yilan bay, this study was to conduct a mesh selectivity experiment with the cover net method during November 2 - December 16, 2004. The mesh size of trawl net at cod end was 7 cm and its outside attached cover net was 3 cm. There are 14 species of fishes and 6 species of shrimps were measured by their selection span which based on their linear biomass were equal and greater 0.5 with a significant difference less than 5% in logistic regression analysis. The fishing efficiency of mesh size of 7 cm and the selection span was differed with the ratio of body width to total length. There were 67.55% of Japanese jack mackerel (Trachurus japonicus) escaped from cod net into cover net. The escape rate for other fishes, Japanese butterfish (Psenopsis anomala), Red bigeye (Priacanthus macracanthus), Largehead hairtail (Trichurus lepturus), Blackmouth croaker (Atrobucca nibe) and Brushtooth lizardfish (Saurida undosquamis) was 38.20, 100.00, 54.60, 35.71 and 54.43%, respectively.