Fifty years of dart tag recoveries for tropical tuna: A global comparison of results for the western Pacific, eastern Pacific, Atlantic, and Indian Oceans

Over the last 50 years, numerous dart tagging programs have been conducted on tropical tunas worldwide. Through these programs more than 1.4 million tunas have been tagged across the Pacific, Atlantic, and, most recently, Indian Oceans with the majority of individuals tagged being skipjack (Katsuwonus pelamis, 858,000 individuals) and yellowfin tuna (Thunnus albacares, 360,000 individuals). The subsequent recovery of 173,574 tagged tunas (skipjack: 94,835, yellowfin: 49,079, and bigeye, Thunnus obesus: 29,660) presents a significant opportunity to obtain a wide range of scientific results. In this paper, we used recovery data from a variety of programs to compare the growth rates from the period between tagging and recovery of three tropical tuna species from four oceanic regions. We also analyzed the maximum time durations between tagging and recovery events as an indication of each species’ longevity, as well as apparent movement patterns and distances traveled by the tuna. Collectively, these comparisons revealed major similarities between tropical tuna species of the basic biological parameters studied. In some instances, our analysis also revealed that the same species show major differences between areas. In addition, this paper also examines the current interest in conducting large-scale, simultaneous tagging of the three tropical tuna species and highlights the importance of improving the quality of recovery data. In particular, there need is paramount to increase the percentage of recoveries that have been fully validated in terms of the fishing zone, recovery date, length and sex of the tagged tunas. Our assessment suggests that large-scale, multi-species tagging programs should become a routine scientific obligation for all tuna regional fisheries organizations, as they are necessary in providing the basic parameters of all stock assessment models.