At the 2018 International Commission for the Conservation of Atlantic Tunas in Dubrovnik, Croatia, a consensus could not be reached by the contracting parties to address the management of the bigeye tuna stock.
The scientific body of ICCAT conducted a bigeye tuna stock assessment in 2018 and concluded that the stock is overfished, and that overfishing is currently occurring. The ICCAT bigeye total allowable catch for major harvesting nations has been reduced from 85,000 metric tons in 2012 to 65,000 metric tons in 2015 with a proposed reduction of 55,000 metric tons that was not implemented. The TAC has been exceeded by approximately 20 percent since 2016.
The United States is not considered a major harvesting nation of tuna, having a threshold of 1,550 metric tons that has never been exceeded, according to landings data. Even though the United States reported that 773 metric tons of bigeye tuna was landed in 2017, we are not part of the global tuna problem and continue to lead the way with conservation measures in our waters.
Bigeye tuna landings in U.S. waters include both landings and discards by recreational anglers and the commercial fleet. Recreational management and/or landings reported by other nations is largely nonexistent, with only commercial landings being reported by most nations; Spain and Portugal reported the most. The international commercial fleet includes the purse-seine and longline fleets and, to a small extent, the so-called artisanal fishery, also known as commercial hook-and-line fishing.
A significant decline in bigeye and potentially yellowfin tuna stocks dates back to the 1990s. This decline was exacerbated by the increased use of fish aggregating devices by the commercial fleet in the Gulf of Guinea located off the northwest coast Africa. The FADs attract fish that include mature skipjack as well as mixed schools of juvenile bigeye and yellowfin tuna. The Gulf of Guinea, a known tropical tuna breeding ground, is also found to hold juveniles. Spatial closures were developed and implemented by ICCAT, but were found to be ineffective in reducing the juvenile bigeye and yellowfin mortality.
The Atlantic international purse-seine fleet has historically increased the harvest of skipjack by utilizing FADs, resulting in exponentially increased landings of juvenile yellowfin and bigeye tuna, partly because of small-mesh nets. The juvenile bigeye and yellowfin tuna are too large to exit these nets and as a result, are landed and sold commercially. Arguably, if the mesh size of the purse were increased, the juvenile bigeye and yellowfin tuna could easily exit the net relatively unharmed, but doing so would make for a less-effective means of harvest for the fleet’s targeted skipjack.
The significant increase in the harvest of juvenile bigeye and yellowfin tuna appears to have changed the size distribution of the stock to what was historically observed before the use of the FADs. In the open ocean, mature bigeye and yellowfin tuna are typically observed in separate schools throughout the water column. However, that does not appear to be the case with purse-seine landings in FAD areas. The scientific data — and logic — dictates management to protect juvenile tuna stocks associated with the use of FADs by said purse-seine fleet.
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South Africa, the United States and several other member nations recommended development of stronger measures to protect juvenile tuna including, but not limited to: seasonal closures; TAC reductions; size limits; and the prohibition or reduction in the use of FADs. Consensus among the contracting parties couldn’t be reached; as a result, there is, unfortunately, no change in the management of bigeye tuna in 2019.
Appropriate measures need to be implemented to protect both bigeye and yellowfin stocks, and the continued lack of proactive action by the governing bodies could negatively impact the U.S. fishery in the future.