Above Water Deterrents Reduce Auk Bycatch in Gillnet Fisheries off the United Kingdom

Seabird bycatch in gillnet fisheries is a globally pervasive conservation issue, yet evidence for effective, scalable mitigation remains limited. In a gillnet fishery off the United Kingdom (1057 sets), we evaluated two above water deterrents (AWDs); “scarybird” kites (“kites” hereafter) and looming-eyes buoys (LEBs) for reducing seabird bycatch. Both AWDs significantly reduced the chance of auk bycatch occurring (kites = −71%, LEB = −59% lower odds of a bycatch event) and magnitude when it did occur (kites = −62%, LEB = −68% reduction in bycatch per unit effort) relative to controls. Kites had a stronger deterrent effect < 30 m from the device whereas LEBs were moderately effective over a broader range. Bycatch peaked in winter, and where net mesh sizes were 100–120 mm, indicating that targeted deployments of AWDs can maximize conservation benefit, while minimizing operational disruption. Given the ubiquity of gillnet fisheries, simple, low-cost AWDs offer a practical route to reducing bycatch and supporting conservation policy.