Exploratory analysis of tagging data to evaluate the benefits of a time-closure area for tropical tunas.

Abstract

Movements of juveniles of tropical tunas were investigated to evaluate the effectiveness of the time-area closures using tag-recapture data. The results show that the apparent movements of juveniles are moderate. Nevertheless, due to the spatial heterogeneity of the tagging operations conducted over time and the different objectives of the previous tagging programs, it was difficult to quantify the exchange rates between the protected areas and the surrounding fishing grounds as well as the resident time spent by juveniles within the protected areas. Consequently, based on the limited tagging information available, there is no evidence that the time-area closures used in the past or proposed recently contribute effectively to the reduction of the fishing mortality for the juveniles of tropical tuna. However, since conventional tagging data may provide critical information useful to evaluate the performance of time-closure areas, we suggest that multispecies tagging program in the future take into account in its objective the study of protected areas for migrating fish and be coordinated by a scientific team in charge of the tagging experiments and in the collect and validation of the tagging information.