Significant underreporting of bycatch and ecosystem impacts in tuna purse seine fisheries

While it is well known that purse seine fleets capture more juvenile tuna and more bycatch species when
setting their nets around drifting Fish Aggregating Devices (dFADs), the broader ecosystem impacts
caused by dFADs are not well quantified. Some research into the bycatch rates associated with tuna
purse seine fishing has aimed to quantify the direct bycatch of animals that is noted by observers aboard
vessels, but many feel that those estimations do not provide the full story of purse seine fleets impacts
upon non-tuna species and their habitats. This is because what an observer records aboard a fishing
vessel that is actively fishing does not capture the entanglement, pollution and direct habitat damage
caused by drifting FADs. Ultimately, quantifying the bycatch captured within a purse seine net when it
is hauled onboard only deals with a potentially small proportion of the real damage actually caused by
drifting FADs, and the survivorship of animals discarded overboard as bycatch has only been lightly
assessed for a few of the species that face these impacts.