In the case of freezer tuna vessels, the capture of juvenile sharks is relatively common. Less frequently, sporadic interactions with mobulids are also recorded. These species are classified as sensitive or vulnerable due to their low biological productivity and their high susceptibility to fishing-related mortality. As a result, these sensitive species must be released back into the sea to continue their life cycle, making every possible effort to minimise the impact of fishing activities on their populations and on marine ecosystems.
AZTI, in collaboration with the tuna fishing sector, has developed tools to enable the safe release of vulnerable species. Release ramps or hoppers installed on board facilitate the return to the sea of unwanted catches, minimising handling and stress on the animals, improving crew safety, and increasing the survival rates of released individuals.
Overall, the results show:
A positive impact of best practices: the implementation of release devices and improved handling protocols significantly increases post-release survival of silky sharks in the purse seine fishery, reaching survival rates of up to 50% for sharks captured and released during fishing trips.
Key factors influencing success: crew experience and vessel structural adaptations, such as the installation of ramps or hoppers, contributed to reducing on-board mortality and improving the physiological condition of released sharks.
Operational challenges: vessel specifications, fishing operations and structural alignment issues highlight the need for vessel-specific solutions tailored to each boat.
Sectors: Fisheries and aquaculture sector
Research lines: Blue Economy, Efficient, sustainable fisheries and aquaculture
Research sublines: Conservation and restoration of marine species and habitats, Sustainable fishery management