Age and growth of albacore tuna (Thunnus alalunga) inthe North Pacific Ocean based on sectioned fin ray

The North Pacific albacore tuna (Thunnus alalunga) is one of the main target species of tuna longline fisheries, and the conservation and management of this species have been increasingly concerned by tuna regional management organizations, such as WCPFC. T. alalunga is a kind of highly migratory species mainly living in the tropical and subtropical waters. This species which lives in the North Pacific Ocean generally spawns at the western and central part of the tropics and subtropics in spring and early summer. In the juvenile period of T. alalunga, a number of albacores migrate from the North Pacific to the temperate waters of the eastern Pacific. The spawns will migrate to the western tropical and subtropical regions of the Pacific to spawn. This set of patterns of movement will be juvenile fish recorded. The migratory characteristics of this species can provide an important basis for its sustainable utilization and management. Since the difficulty of sample collection, studies for the age identification of the North Pacific T. alalunga were few. Therefore, we studied the age and growth of T. alalunga in the North Pacific by the species’ spines data from the survey of the long-spines tuna fishery in the North Pacific during the years of 2013 and 2014. The fin rays are the newest manifestation of the biological information of T. alalunga in the North Pacific, providing useful information for the sustainable utilization and management of T. alalunga in the North Pacific. Information on the age and growth is very important for conducting stock assessment of this species. Based on 258 fin ray samples collected on the Chinese tuna longliner " Tianxiang 16” operated in the North Pacific between October 19, 2013 and April 5, 2014, the age and growth of the North Pacific T. alalunga were studied. Three different cutting positions were involved in the processing of section selection, and three functions, the linear function, exponential function and exponential function respectively, were also used to fit the relationships between the fork length and fin ray radius. The Von Bertalanffy growth function of the North Pacific albacore was L_t=112.231×1-e^{–0.277(t+1.435)}.