摘要：

This paper analyzes the relationship between yellowfin tuna (Thunnus albacores) 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.

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