UW Aquatic & Fishery Sciences Quantitative Seminar

Maite Pons

School of Aquatic & Fishery Sciences, UW

Status and management of tunas and tuna-related species

Abstract

Commercial tunas and billfishes (swordfish, marlins and sailfish) provide considerable catches and income in both developed and developing countries. Tuna is worth more than $42 billion dollars to the annual global economy which is more than the gross national product of 108 of the world’s countries. Because they are large migratory species, they are managed by Regional Management Organizations (RFMOs). These stocks vary in status from lightly exploited to rebuilding to severely depleted. Here, we used random forest analysis to analyze the effect of different factors associated with life history characteristics, economics and management in the current stock status of tunas and billfishes. Also, we measure the intensity of fisheries management of the RFMOs using a fisheries management index (FMI), and we evaluated which are the main factors that affect this index for each RFMO and different stocks. We found that, particularly for tunas, stocks were more depleted if they had high commercial value, were long-lived species, had small pre-fishing biomass and were subject to intense fishing pressure for a long time. In addition, among other management measures, implementing and enforcing total allowable catches (TACs) had the strongest positive influence on rebuilding overfished tuna and billfish stocks. Moreover, among tunas RFMOs, the ones that had the lowest intensity of fisheries management are those that have countries members with low GDP, more number of vessels and with fisheries that are still developing. At a stock level, stocks that are under management plans and enforce limits in fishing pressure presented the highest FMI values. The most intensively managed stocks were those that are more depleted but that are showing signs of rebuilding or are already rebuilt. Some bycatch species, such as some marlins, sailfish and sharks, and small tunas, were the ones that have the lowest intensity in fisheries management.