印度洋大眼金枪鱼、黄鳍金枪鱼延绳钓渔场重心变化分析

Analysis on barycenter of fishing ground for bigeye tuna and yellowfin tuna by lonelining in the Indian Ocean

大眼金枪鱼和黄鳍金枪鱼是印度洋金枪鱼延绳钓的主要渔获种类。通过计算以渔获量为权重的经度和纬度的加权平均值即渔场重心和利用空间距离分析方法,分别对1967-1987年、1988-2004年两个时间段的印度洋大眼金枪鱼、黄鳍金枪鱼延绳钓渔场重心的年内、年际变化规律和各月渔场重心空间聚类情况进行研究。研究表明,渔场重心在年内呈现出规律性变化,大眼金枪鱼月重心变化1-4月向西北移动,5-8月向东南方向移动,9-12月向东北方向移动;黄鳍金枪鱼月渔场重心变化1月向西北移动,2-4月向西移动,5-8月份向东南移动,9-12月份向东北移动,这在一定程度上反映了印度洋大眼金枪鱼、黄鳍金枪鱼的洄游规律。渔场重心的年间变化受到了海洋环境条件变化所引起的南方涛动现象(ENSO)的影响,大部分发生ElNio的当年或次年,年渔获量分布重心会向南、向西移;发生LaNia的年份前后渔获量分布重心会向北、向东移。同时捕捞行为也对渔场重心的年间变化产生影响。

Bigeye tuna （ Thunnus obesus） and yellowfin tuna （ Thunnus albacares） are major fishing targets by longline in the Indian Ocean. Through the weighted average of catch in latitude and longtitude （ barycenter of fishing ground） and analysis of spatial distribution, it is studied on the laws of annual and inter-annual change of barycenter of fishing ground and the analysis of barycenter of fishing ground in each month by cluster of bigeye tuna and The barycenter of ellowfin tuna longline fisheries in the Indian Ocean during 1967 - 1987 and 1988 -2004. fishing ground for bigeye tuna turns to the northwest from January to April, to the southeast from May to August, to the northeast from September to December and the barycenter of fishing ground for yellowfin tuna turns to the northwest in January, to the west from Feberary to April, to the to August, to the northeast from September to December, which show that the change law southeast from May of barycenter during the year, to a certain extent, reflects the migratory pattern of bigeye tuna and yellowfin tuna in the Indian Ocean. The change law of barycenter inter-annually moving to the west and the south in the same year or in the next year of the El Nino and moving to the east and the north in the same year or in the next year of the La Nina had been influenced by the effect of Southern Oscillation （ENSO） caused by the changes of marine environment conditions and the fishing practice is another factor.