Stick water as potential seabird attractor to krill fishing operations: a review of evidence addressing olfactory cues used by Procellariforms for navigation and foraging

Conservation Measure 25-03 (2023) prohibits the discharge of offal and discards during the shooting and hauling of trawl gear but allows the discharge of 'stick water' (liquid discharge by-product of processing of the catch) understanding that does not constitute a source of food and does not attract seabirds to fishing vessels. In 2023, WG-IMAF recalled the existence of research on seabird olfactory sense and questioned if stick water could be attractive to seabirds. The Scientific Committee encouraged the further consideration of issues associated with the discharge of stick water associated with seabird attendance to fishing operations. This paper reviews relevant scientific literature on this matter, aiming to assist WG-IMAF and the Scientific Committee in discussing the effect that stick water may have as seabird attractor in krill fishing operations. Available information indicates that pyrazines (scented compounds in macerated krill) are attractive to several procellariform species important in the Antarctic and Subantarctic ecosystems. These scented compounds are released when krill are macerated or damaged, a situation that is likely to occur when krill swarms are preyed upon by diving predators, and as a result of fishing operations. WG-IMAF may find this information relevant when analyzing the merit of amending CM 25-03 (2023), in particular footnotes 3 and 4 in the Conservation Measure.