大西洋金枪鱼延绳钓主要兼捕鱼种垂直分布结构研究

VERTICAL DISTRIBUTION OF BYCATCH SPECIES CAPTURED BY TUNA LONGLINE FISHERY IN THE ATLANTIC OCEAN

研究延绳钓渔获物的垂直分布结构对于评估延绳钓渔业对目标和兼捕种类的影响具有重要的理论和实际参考价值。根据2007-2010年间2个航次调查采集的热带大西洋公海海域(05°N～15°N,29°W～41°W)金枪鱼延绳钓主要兼捕鱼种的渔获资料,估算了14种渔获物的钓获深度,包括金枪鱼类3种、旗鱼类3种、鲨鱼类3种、其它鱼类3种、海龟2种。当钓钩上浮率假设分别为15%、20%和25%时,最小估算深度分别为122、114和107m,最大估算深度分别为311、293和275m。叉尾长鳍乌鲂的平均钓获深度最深,海龟类的平均钓获深度最浅。四分位距图(IQR)显示,各物种的深度分布范围变化很大,有些种类之间的深度分布中值虽然相近,但深度分布范围却相差很大。除剑鱼外,其余兼捕物种与大眼金枪鱼的深度分布均值均有显著性差异。而除剑鱼和红棱鲂外,其余兼捕物种与大眼金枪鱼的深度分布函数均有显著性差异。聚类分析显示14种渔获物可以分成3种垂直分布结构。

Information of vertical distribution of pelagic species has important value for the assessment of impact of longline fisheries on target and bycatcb species. Based on capture hook data of pelagic species in two longline scientific observer trips in the high sea of tropical Atlantic Ocean during 2007-2010, we estimated the capture depths of 14 species, including three species of tunas, three species of billfishes, three species of sharks, two species of sea turtles and others. When the constant shoaling factors were 15 %, 20 % and 25 %, the minimum estimated depths were 122,114 and 107m, and the maximum estimated depths were 311,293 and 275m, respectively. The species with the deepest capture depth was bigscale pomfret. The species with the shallowest capture depth was sea turtles. Interquartile range map （IQR） showed the depth distribution of each species varied greatly. Except for sword- fish, the mean depths of the bycatch species were significantly different from that of the bigeye tuna. Except for swordfish and dagger pomfret, the depth distributions of the bycatch species were significantly different from that of the bigeye tuna. Cluster analysis showed that there were three vertical distribution structures among the 14 species.