Responsible tuna fishing as a guarantee of sustainable future

A study by the Spanish tuna fleet confirms low contribution of purse seine to fishing mortality or protected species compared to other gears

A study by the Spanish tuna fleet confirms low contribution of purse seine to fishing mortality or protected species compared to other gears

A study by the Spanish tuna fleet in the Indian Ocean, three years after the inception of its Code of Good Practices, integrated in its Fisheries Improvement Project (FIP), shows that the contribution of the purse seine gear to the mortality of main bycatch species is practically null, as compared to that recorded by other gears, such as longlines and drift nets. This study estimates levels of fishing mortality at 0,15%, for sharks and rays (generically known as Chondrichthyes), less than 0,3%, for turtles and null for marine mammals.

This data, recently submitted by the Producers’ Organization of Large Freezer Tuna Vessels (OPAGAC) to the Indian Ocean Tuna Commission (IOTC), also show that, in the case of silky sharks, the most important bycatch species for purse seiners, the mortality represents only around 1,3% of the total fishing mortality.

On the opposite side of purse seine fishing, the study identifies driftnets as the gear contributing the most to the mortality of those species in the Indian Ocean. Thus, driftnets account for practically all marine mammal and whale shark mortality, over 50% of Chondrichthyes mortality, and over 40% of sea turtle mortality. Longlines would be responsible for the rest. According to OPAGAC, these figures are subject to large uncertainty, considering the paucity of the data available for those two fisheries.

According to OPAGAC, the main reason for the low fishing mortality of bycatch on purse seiners is the much lower proportion of bycatch recorded on purse seine sets, as compared to other fishing gears. Furthermore, the voluntary implementation by the fleet of a Code of Good Practices, verified by the technological institute AZTI and integrated into the Fisheries Improvement Project (FIP) launched in 2016 in collaboration with WWF, has contributed to further reduce the mortality of these species, with an additional estimated 10% reduction in average.

The Code includes provisions on the use of non-entangling fish aggregating devices (FAD) -of which the Spanish fleet uses more than 90% in the Indian Ocean- and the implementation of safe release practices for protected species. This has contributed to a greater survival of species caught in each set and to the almost total elimination of ghost fishing, which was caused by FAD nets and presumed very high in the past.

According to Miguel Herrera, deputy manager of OPAGAC, “for many years, purse seine tuna fleets, especially those relying on FADs, as is our case, have been on the spotlight for their alleged high contribution to the mortality of various protected species. This study shows that the efforts undertaken by some fleets, such as the Spanish, to reduce the incidental mortality of protected species in the Indian Ocean is paying off.”

Lack of transparency

The study identifies lack of data as the main issue affecting a large number of longline and drift gillnets fleets and hampering the management of bycatch species in the Indian Ocean, mainly due to the nil or very low levels of observer coverage on those fleets. Observer coverage for those fleets barely reaches 1,5% of the fishing operations, well below the minimum 5% established by the IOTC, and the 100% recorded on all tuna purse seine vessels flying European Union and Seychelles flags.

In light of the results, OPAGAC stresses the need for IOTC members and cooperating parties (CPC) to focus its attention on improving compliance with minimum requirements for data collection and dissemination, especially those having longline and gillnet fisheries.

The study, which can be consulted on the IOTC website, is one of the actions implemented by OPAGAC to assess the impact of its fleet on bycatch and evaluate and the efficiency of the actions implemented to mitigate the impact of the fleet, as contemplated in the OPAGAC FIP, which covers also similar actions in other oceans. In addition, OPAGAC will collaborate with NGOs and scientific institutions to extend the study in the Indian Ocean so that an updated document can be presented to the IOTC Working Party on Ecosystems and Bycatch in 2019.


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