Effect of two natural repellents on the depredation of mackerel baits by white-chinned petrels (Procellaria aequinoctialis)

Longline fisheries worldwide have interactions that can be harmful or fatal to seabirds. We report preliminary testing of potential seabird deterrents in longline fisheries around the sub-Antarctic Kerguelen Islands. We compared White-chinned Petrel (Procellaria aequinoctialis) responses to mackerel (Scomber scombrus) baits treated with capsaicin and piperine mixtures, and untreated baits. Petrels readily consumed all untreated baits. However, there were significant differences among the six categorised responses to treated baits (capsaicin mixture: ?5 = 161.71, P < 0.001; capsaicin and piperine mixture: ?4 = 114.40, P < 0.001). Petrels rarely immediately swallowed treated baits (1.6% of treated baits), but vigorously ‘washed’ their bills in water after swallowing treated baits (21.9% of treated baits), manipulated the treated baits prior to swallowing and washing their bills in seawater (27.4%), manipulated then abandoned treated baits (21.9%), and sometimes ignored treated baits completely (27.1%). These results suggest that with further testing and development, treated baits could be effective in reducing seabird attacks on baited hooks, consequently reducing seabird bycatch.