大西洋中部黄鳍金枪鱼(Thunnus albacares)的垂直分布与有关环境因子的关系

RELATIONSHIP BETWEEN VERTICAL DISTRIBUTION OF YELLOWFIN TUNAS' (THUNNUS ALBACARES)AND THE CONCERNED ENVIRONMENTAL FACTORS IN THE CENTRAL ATLANTIC OCEAN

根据 2 0 0 1年 6— 1 0月在大西洋中部大洋性金枪鱼延绳钓作业中观测到的黄鳍金枪鱼的上钩钩号 ,应用悬链线钩深计算公式分别计算出各钩号的钩深 ;根据STD仪测得的温度、盐度的垂直分布以钩深为引数 ,查出该尾鱼捕获水深处的温、盐数据 ;根据黄鳍金枪鱼的取样数据 ,推算出各水层、各水温段、各盐度段的渔获率。渔获率最大的水层、水温段、盐度段为黄鳍金枪鱼的最适水层、水温段、盐度段 ;渔获率为前 3位的水层、水温、盐度段为黄鳍金枪鱼活动较频繁的水层、水温段、盐度段。结果表明 ,在大西洋中部 ,黄鳍金枪鱼的最适水层为1 5 0 0 0— 1 79 99m ,最适水温段为 1 3 0 0— 1 3 99℃ ,最适盐度段为 35 4 0— 35 4 9;大西洋中部渔场黄鳍金枪鱼活动较频繁的水层为 1 2 0 0 0— 2 0 9 99m ,水温段为 1 2 0 0— 1 4 99℃ ,盐度段为35 2 0— 35 4 9。

This paper analyzes the relationship between yellowfin tuna (Thunnus albacares ) vertical distribution and the temperature, salinity in the Central Atlantic Ocean. The hook depth was calculated using the catenary curve hook depth equation according to the hook number of the hooked fish observed from June to October 2001. The temperature and salinity of the hooked fish's swimming depth was calculated from temperature and salinity vertical profiles measured by the STD guided by the hook depth. From the sample data,it was defined that depth ranged from 120.00m to 359.99m with 30m intervals, water temperature ranged from 10.00℃ to 16 99℃ with 1 0℃ intervals and the salinity range was from 35.00 to 35.69 with 0.10 intervals. There were, in total, 8 depth ranges, 7 ranges in water temperature and 7 ranges in salinity. The catch rate of the tuna at different depths, temperatures and salinities were estimated. The range of depth, water temperature and salinity with the maximum catch rate of yellowfin tuna indicated the optimal swimming depth, water temperature and salinity range of the fish. The range of depth, water temperature and salinity with the first 3 highest catch rates indicated the common swimming depth, water temperature and salinity range. The results indicate that in the Central Atlantic Ocean the optimal swimming depth, water temperature and salinity range of the yellow fin tuna were found to be 150.00—179.99m,13.00—13.99℃,35.40—35.49 respectively. The common swimming depth, water temperature and salinity range were 120.00—209.99m,12.00—14.99℃, 35.20—35.49 respectively. Conclusions from this research can be applied to fishing practices in order to target yellowfin tuna, hooks should be laid to one of the indexes of depth range, water temperature range and salinity range. Generally, the depth range of the water temperature range and salinity range with the maximum yellowfin tuna catch rate corresponds to the depth range with the maximum catch rate. If any disparities exist between the depth range, the water temperature range, and the salinity range, the water temperature range should be considered as the main factor. Due to the limitations in sampling size and the restrictions, this research is at a preliminary stage. Further investigations should be made particularly regarding the relationship between catch rate and the dissolution of oxygen. Precision of results would also be improved if TDRs were used to measure the actual water temperature and salinity of the water layer where the fish are caught.