根据2012年7～11月金枪鱼科学观察员在中西太平洋采集的钩位深度以及渔获物的钓获钩位数据，分析了各钩位的上浮率和钓获鱼种的垂直分布结构，并比较了不同鱼种垂直分布的差异性。结果表明：（1）钓钩绝对上浮率变化范围为0．49～44．73 m，相对上浮率的变化范围为0．65％～16．69％，平均绝对上浮率为23．29 m，平均相对上浮率为8．87％。（2）12种主要渔获钓获深度范围差异很大，大'（Lampris guttatus）的平均钓获深度最浅，为75．92 m，蓝枪鱼（Makaira nigricans）的平均钓获深度最深，为228．19 m。聚类分析显示12种主要渔获物可以分成3种垂直分布结构。（3）11种主要兼捕渔获钓获深度均与长鳍金枪鱼（Thunnus alalunga）钓获深度呈显著性差异。%Albacore(Thunnus alalunga),one of the main target species of commercial tuna fishery,has great economic value and a long history of scientific research.However,studies on vertical distribution of pelagic species are rare in China,and this is the first time to study the vertical distribution of pelagic species in the Western and Central Pacific at home and abroad.Information of vertical distribution of pelagic species is important for the development of effective measures to mitigate bycatch, and very helpful for better understanding of the oceanic ecosystem structure and implementation of ecosystem-based fisheries management.Learning this relationship will have a significant impact on both commercial fishing and sustainable development of resource.Data were collected by scientific observer in the Western and Central Pacific from July to December 2012.The operating range was from 06°50′S to 18°00′S,and from 160°48′W to 173°08′W,near the sea of Solomon Islands.There were 98 sets altogether in this area.The catch data contained catch species,fork length,set locations and fishing gear information like length of float line,length of branch line,main line length between branch lines and so on.The data of fishing gear were used to calculate caught depth by catenary equation.The actual average depth of each hook was measured based on the depth data recoreded by TDR.Based on depth data of longline hook recorded by TDR and capture hook position of pelagic species,shoaling rate of longline hook and vertical distribution were analyzed.The results were as follows:the absolute shoaling rate range of longline hook was 0.49 -44.73 m,and the average absolute shoaling rate was 23.29 m.The relative shoaling rate rang of longline hook was 0.65%-16.69%, and the average relative shoaling rate was 8.87%.The depth ranges of 12 main species were different.The species with the deepest depth was blue marlin (Makaira nigricans),and the species with the shallowest depth was Great barracuda (Lampris guttatus ).Cluster analysis showed that there were three vertical distribution structures among 12 main species;the first class with the shallowest depth was common dolphinfish (Coryphaena hippurus),great barracuda(Sphyraena barracuda),wahoo(Acanthocybium solandri);the second class with deeper depth was escolar (Lepidocybium flavobrunneum ),pelagic stingray (Dasyatis violacea ), albacore tuna (Thunnus alalunga ),yellowfin tuna (Thunnus albacares ),slender mola (Ranzania laevis ), skipjack tuna (Katsuwonus pelamis );the third class with the deepest depth was bigeye tuna (Thunnus abesus),longnose lancetfish(Alepisaurus ferox),blue marlin(Makaira nigricans);the mean depth and depth distributions of bycatch species were significantly different from that of the targeted albacore tuna.Those results show that the theoretical depth of the catenary equation has a certain reference value in the Western and Central Pacific.Deploying longline hooks at appropriate depths can greatly improve catch of target species,and reduce bycatch of protected species and untargeted species.
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