A study by the Spanish tuna fleet in the Indian Ocean, three years after the introduction of its Code of Good Practice, integrated into its Fisheries Improvement Project (FIP), shows that the contribution of the purse seine gear to the mortality of main by-catch species is practically zero, compared to figures recorded for other gears such as longlines and drift nets. This study estimates levels of fishing mortality at 0.15%, for sharks and rays (Chondrichthyes), less than 0.3%, for turtles and zero for marine mammals.
This data, recently provided by the Producers Organisation of Large Freezer Tuna Vessels (OPAGAC) to the Indian Ocean Tuna Commission (IOTC), also demonstrates that in the case of silky sharks, the largest by-catch species for purse seiners, the mortality represents only around 1.3% of the total fishing mortality.
The study identifies drift nets as the gear contributing the highest mortality of those species in the Indian Ocean, and that drift nets account for practically all marine mammal and whale shark mortality, over 50% of Chondrichthye mortality, and over 40% of sea turtle mortality. Longlines are judged to be responsible for the remainder.
According to OPAGAC, these figures are subject to significant uncertainty, considering the paucity of the data available for those two fisheries.
OPAGAC states that the main reason for the low by-catch mortality demonstrated by purse seiners is the much lower proportion of by-catch recorded in purse seine sets compared to other fishing gears.
In addition, the voluntary implementation by the fleet of a Code of Good Practice, verified by 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 on average.
The Code includes provisions on the use of non-entangling fish aggregating devices (FADs), 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 is presumed to have been very high in the past.
‘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,’ said OPAGAC deputy manager Miguel Herrera.
‘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.
Transparency shortfall
The study identifies lack of data as the main issue affecting a large number of longline and drift gill nets fleets and hampering the management of by-catch species in the Indian Ocean, mainly due to the non-existent or very low levels of observer coverage on those fleets. Observer coverage for those fleets barely reaches 1.5% of fishing operations, well below the minimum 5% established by the IOTC, in complete contrast to the 100% recorded observer coverage 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 gill net 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 by-catch levels and to evaluate the efficiency of the actions implemented to mitigate the impact of the fleet, as set out in the OPAGAC FIP, which covers also similar actions in other oceans.
OPAGAC has pledged to continue collaboration 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.
OPAGAC is an association of nine tuna freezer purse seine companies. This fleet, consisting of 47 purse-seine tuna vessels, harvested 380.000 tonnes annually, accounting for 8% of the worldwide catch, and operates in Atlantic, Indian and Pacific Ocean waters, within the jurisdiction of the four main Regional Fisheries Management Organisations for this type of fishing; the International Commission for the Conservation of Atlantic Tunas (ICCAT), the Indian Ocean Tuna Commission (IOTC), the Inter-American Tropical Tuna Commission (IATTC) and Western and Central Pacific Fisheries Commission (WCPFC).
