Assessing Barotrauma Treatments of Cusk (Brosme brosme) Bycaught in the Maine Lobster Fishery

Non-targeted species account for an estimated one-quarter of the world’s fisheries catch, leading to wasted valuable resources, a potential threat to rare or endangered species, and unaccounted fishing pressure on exploited stocks. The Maine lobster fishery is responsible for an unknown quantity of cusk (Brosme brosme) bycatch which is a Species of Concern and candidate for the Endangered Species Act. Cusk experience barotrauma, physical trauma induced by gas expansion from decompression, during surfacing events such as hauling up a lobster trap. Maine state law mandates lobster harvesters to discard non-targeted species caught in their traps. Upon discarding, cusk are positively buoyant and are incapable of quickly changing their buoyancy which prevents them from returning to depth to avoid predation from birds and seals. Past research has demonstrated that assisted recompression or venting of barotraumatized fish increases their chance of survival. In this research, collaborative experiments are being conducted with volunteer Maine Lobstermen to create protocol for discarding methods of cusk to increase their survivability after a surfacing event. Cusk will be recompressed using lobster traps after a timed duration on deck and monitored with underwater cameras to record their behavior. Venting cusk by using a hypodermic needle to release trapped air will also be tested as a method or treatment for barotrauma. The survival rates of discarded cusk will be evaluated in the experiment. This study aims to develop protocol to increase survivability of bycaught cusk thus reducing the unintended mortality of these species in the Maine lobster fishery.