FISHERY IMPACTS ON STOCK | HABITAT IMPACTS | BYCATCH | MANAGEMENT EFFECTIVENESS
Fishery Impacts on Stock
Yellowfin tuna is widely distributed throughout tropical and subtropical oceans. They are highly fecund with a moderate lifespan, making them fairly resistant to fishing pressure. A Seafood Watch report from 2014 stated that there is uncertainty about yellowfin tuna populations in the Atlantic as well as some indication that they are overfished and unsustainably fished. Seafood Watch also reported that yellowfin tuna are overfished in the eastern Pacific Ocean but healthy in the western and central Pacific. In the Indian Ocean, yellowfin populations are healthy and fishing mortality rates are low.
Yellowfin tuna are caught in fisheries that target other tuna species. Slightly more than half of all tuna landed worldwide, including yellowfin, is caught with purse seines that have minimal impacts on ocean habitats. However, anchored fish aggregating devices (FADs) could result in contact. The pelagic longlines, trolls and poles used to catch yellowfin tuna also present a low risk to the seabed and bottom habitats, according to Seafood Watch.
Extent of Bycatch
With the exception of the troll, pole and handline fisheries, bycatch in yellowfin fisheries is high. Unintended catch includes threatened and endangered marine mammals. Dolphins, sea turtles, sharks, other tuna, marlin, manta rays, wahoo, stingrays and juvenile tunas are among the bycatch, which is increased with the use of fish aggregating devices (FADs). Longline tuna vessels in the Atlantic are required to collect and report bycatch and discard information. They must have equipment for the safe handling, disentanglement and release of sea turtles, and the captain must be trained on correct techniques.
Starting in 2013, countries in the Atlantic that have not reported shortfin mako shark catch data are prohibited from catching them, according to a 2014 Seafood Watch report. Although fishermen back down purse seine nets for dolphins to escape in the eastern Pacific, the animals can still die from net canopy collapses and stress. The deaths are declining but dolphin populations haven’t yet recovered.
Yellowfin are managed by several fishery management organizations worldwide. The International Commission for the Conservation of Atlantic Tunas (ICCAT) manages them in the Atlantic. ICCAT’s tuna conservation and management program was amended in 2011 to include yellowfin but recovery plans have not been in place long enough to judge their success. Seafood Watch rated the Commission’s bycatch strategy “ineffective” because it doesn’t meet best practices. In addition, there are no bycatch cap or catch limits.
Yellowfin tuna are managed in the U.S. and Canadian longline fisheries by the National Marine Fisheries Service and Fisheries and Oceans Canada. While Seafood Watch rated most of the management strategies as moderately effective, the bycatch strategy was called ineffective in the Canadian North Atlantic longline fishery because it does not require best practices for reducing incidental shark capture. Observer coverage was also lacking.
In the Pacific, the Inter-American Tropical Tuna Commission (IATTC), the Western and Central Pacific Fisheries Commission (WCPFC), the Western Pacific Regional Fishery Management Council (WPRFMC) and the state of Hawaii all manage tuna. Management measures in the western and central Pacific Ocean longline fishery, including ones mitigating bycatch, were rated moderately to highly effective in a 2014 Seafood Watch report. However, management in the eastern Pacific longline fishery did not meet best practice requirements and scientific advice was not always followed, according to a separate report.
Seafood Watch rated the management in the western, central and north Pacific yellowfin purse seine fishery between ineffective and moderately effective. The WCPFC lacks limits on the number of FAD sets allowed annually.
The Indian Ocean Tuna Commission (IOTC) and the Sri Lankan Ministry of Fisheries and Aquatic Sciences manage tuna in those regions. The management was given a red score by Seafood Watch due to a lack of measures to improve monitoring, a lack of total allowable catch, lack of bycatch data as well as poor bycatch mitigation. Seafood Watch also pointed to IUU fishing issues in the Indian Ocean.