Kress explains: "Most seabirds catch fish and then regurgitate them to feed their young.
An estimated 27% of seabirds caught during setting by Japanese longline tuna vessels operating off of Tasmania, Australia, were not hauled aboard [8].
Gilman et al. [25] found that in the Hawaii longline tuna fishery 34% of seabirds caught during setting were not hauled aboard.
In addition to the need to account for all seabirds caught during longline fishing operations, to provide a more precise input for population models, estimates of seabird mortality in longline fisheries require adjusting to also account for delayed mortality of a proportion of seabirds caught but freed from gear, and mortality caused by hooks discarded in offal [19].
For example, conservationists might ask, 'How can we reduce fulmar by-catch at sea?' They could look at the assessments of five interventions designed to reduce seabird by-catch, each of which has been tested on species including fulmars.
Or they could look at the assessments of 22 interventions that aim to reduce seabird by-catch but that haven't all been tested on fulmars specifically.
At sea, procellariids threatened by long-line fisheries can be protected using techniques such as setting long-line bait at night, dying the bait blue, setting the bait underwater, increasing the amount of weight on lines and using bird scarers can all reduce the seabird by-catch.
For the southern Benguela and Agulhas Bank ecosystems, more research would be beneficial on how spatial protection influences pelagic breeding seabirds, fisheries catch and bycatch species.
Thus, more than 50% of seabirds observed caught during setting were not attached to the gear when retrieved.
Some seabirds observed caught during the set may have eventually dislodged the hook, or untangled from the line, and escaped [25].
In a subsequent study in the Hawaii longline tuna and swordfish fisheries, Gilman et al. [20] found that 28% of seabirds observed caught during setting were not hauled aboard.
