Determination of Age and Size at Sexual Maturation of Yellowfin Tuna (\u3cem\u3eThunnus albacares\u3c/em\u3e) in the NW Atlantic Ocean

This report examines sexual maturation of yellowfin tuna (Thunnus albacares; YFT) above 35° North in the western Atlantic Ocean. The majority of samples were collected near Oregon Inlet, North Carolina with additional samples from New England to determine if there is a difference in maturation with latitude. Maturation was determined by gross classification of gonads as well as histological examination. Data were compiled based on sex and fish length to elucidate trends. Females collected at lower latitudes were found to have a lower GSI and gonad weight than those from higher latitudes. Males in both locations had a similar GSI and gonad weight based on the length of the fish. At higher latitudes, female fish were immature up to the largest fish collected (124 cm straight fork length (SFL)). Despite fish at lower latitudes having a lower gonadosomatic index (GSI) and gonad weight, beginning stages of oocyte development were present only in females ranging from 110-116 cm SFL in these locations. Overall, female fish were found to be in different stages of immaturity whereas a number of male fish were ready to spawn, suggesting that males may mature at a smaller size than females in both locations. In North Carolina, males ranging from 96-121 cm SFL were found mature, but only males ranging from 127-130 cm SFL were mature in New England. Results of this study are consistent with other studies that show size selectivity by angling gear and a delay in YFT maturation at higher latitudes