The sea around Andaman and Nicobar islands is one of the best tuna fishing ground and catches of yellowfin tuna forms a major constituent of Tuna longline fishery. The present study is an attempt to evaluate the effect of the lunar cycle and monsoon on the catch rate of yellowfin tuna based on exploratory tuna longline survey carried out by M.V. Blue Marlin , Fishery Survey of India, Port Blair. Present study provided information on the abundance of resources in time and space, environmental factors affecting its distribution and its significance in abundance of yellowfin tuna. The results of the present study indicated that there is a significant effect of the lunar cycle on the catch rate of yellowfin tuna occurring in the Andaman and Nicobar waters. The result showed that monsoon also significantly affects the catch rates of yellowfin tuna. Downward trend of year wise catch rate noticed during the study period warrant strict management measures on the tune longline fishery.

Yellowfin tuna, catch rate, abundance, lunar & monsoon effect, Andaman Sea.