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

底拖網為一種無選擇性及高混獲率的漁具，為瞭解臺灣北部海域底拖網漁船對未成熟魚的漁獲影響，利用水試所「海富」號試驗船於2009年3月至11月進行4航次27網次的底拖網網目選擇性試驗，所使用的袋網與覆蓋網網目分別為 7.5cm及 2.1cm。以漁獲物生物量大於或等於 0.5的種類進行體長選擇範圍及選擇係數估計，結果顯示本種網目規格可使95.66%未達成熟之花斑蛇鯔 (Saurida undosquamis) 自袋網中逃逸，而小黃魚 (Larimichthys polyactis)、白姑魚 (Pennahia argentata)、真鰺 (Trachurus japonicus)、細點圓趾蟹 (Ovalipes punctatus)、黑口 (Atrobucca nibe)及劍尖槍烏賊 (Uroteuthis (P.) edulis) 等幼魚之逃逸率分別為93.06%、90.57%、78.53%、50%、48.02%及43.02%，顯示若能擴大袋網網目為75mm，對於花斑蛇鯔等七種魚種將可提供至少一次的生殖機會。
海域試驗調查部分，99年度計進行 4航次44網次作業，出現種類有112科 279種，其中魚類79科192種、蝦類 6科23種、蟹類10科34種、軟體動物12科25種、其它類包括劍尾類 1科 1種、海星 2科 2種、海膽 1科 1種、海鰓 1科1種。單位努力漁獲量於春季航次14.24kg/hr (10.27 ~ 17.88 kg/hr)、夏季航次為15.32kg/hr (7.13 ~ 30.76 kg/hr)、秋季季航次為52.5kg/hr (9.79 ~ 112.0kg/hr)、冬季航次正分析中。
宜蘭灣海域產花斑蛇鯔的生殖腺指數 (GSI) 月別變化情形顯示，雌性個體的GSI值由 2月開始上升，隨後開始下降而於 9月以後降至相對低值，而雄性花斑蛇鯔之GSI值則變動不大，推斷花斑蛇鯔之生殖季節在每年2-9月之間。
以豐度生物量比較曲線評估南寧漁港底棲混獲魚類群聚之現況，月別豐富度、均勻度及歧異度有相同的趨勢，其中歧異度及均勻度以9月及7月最高，分別為3.11及0.84；豐富度則以6月最高為6.45。月別的ABC曲線顯示4、5月的豐度優勢度曲線高於生物量優勢度曲線，表示本海域魚類群聚處於嚴重干擾狀態；7-9月之豐度優勢度曲線則與生物量優勢度曲線相交。

A. Mesh selectivity of trawl net
Bottom trawler is a fishing method with unselective and high bycatch rates. In order to find out the catch rate of immature fish caught by bottom trawler in northern waters off Taiwan, a mesh selectivity experiment was conducted by R/V Hai-Fu (Fisheries Research Institute) with 27 experimental hauls in four cruises during March to November, 2009. The mesh size of trawl net at cod end was 7.5cm and its outside attached cover net was 2.1cm. The selection spans and factors of species with biomass large/equal to 0.5 were measured. The escape rate of lizard fish (Saurida undosquamis) from cod net into cover net was 95.66%. And the others of yellow croaker (Larimichthys polyactis), silver croaker (Pennahia argentata), Japanese jack mackerel (Trachurus japonicus), sand crab (Ovalipes punctatus), black month croaker (Atrobucca nibe) and swordtip squid (Uroteuthis (P.) edulis) was 93.06, 90.57, 78.53, 50, 48.02 and 43.02%, respectively. As the results, expanding the mesh size of cod end to 75 mm may afford more than one chance to spawn for seven species such as lizard fish.
B. Survey of demersal fish resources in northern waters off Taiwan
The investigation on species composition in the northern waters off Taiwan was conducted in 2010 with 44 hauls in 4 cruises. All specimens of 279 species of 112 families were recorded and including 192 species of 79 families of fishes, 23 species of 6 families of shrimps, 34 species of 10 families of crabs, 25 species of 12 families of molluscs, 1 species of 1 family of horseshoe crab, 2 species of 2 families of sea star, and 1 species of 1 family of sea pen. The CPUE of 2010 year were 14.24 kg/hr (10.27~17.88 kg/hr) in spring, 15.32 kg/hr (7.13~30.76 kg/hr) in summer, 52.5 kg/hr (9.79~112.0 kg/hr) in autumn, and the result of winter cruise was analyzing.
C. Reproductive character of the Lizard (saurida undosquamis) in Ih-Lan Bay, Taiwan.
The monthly variation of gonadosomatic index (GSI) of lizard fish, collected from I-lan bay, indicated that increased at February and decreased to relative low value at September in female, but with less variation in male. We suggested that the spawning season of lizard fish was estimated as February to September.
D.Analysis the demersal fish assemblages in Ih-Lan Bat, Taiwan.
Abundance biomass comparison (ABC) curve were applied to analyze the data collected from Nan-ning fishery harbor for assessing the demersal fish assemblages in I-lan bay. Cluster analysis showed the same trend in abundance, evenness, and diversity in each month. The highest value of diversity, evenness, and abundance were 3.11, 0.84, and 6.45 in September, July, and June, respectively. The abundance curves were above the biomass curves in April and May, or the curves intersected in July to September, indicated that the present fish community was affected.