Evaluating the Effectiveness of the Northeast Gear Marking Scheme for Aerial Detection of Large Whale Entanglements: Implications for North Atlantic Right Whale Conservation

Abstract

Interactions with fixed fishing gear represents an ongoing and significant cause of serious injury and mortality for baleen whales. Specifically, the North Atlantic right whale is critically endangered, and over 85% of the remaining individuals have experienced entanglement at some point in their lifetime. Effective mitigation of entanglement risk requires accurate attribution of gear sources involved in large whale entanglements. Currently, the Northeast gear marking scheme requires state-specific color markings on buoy lines in trap/pot and gillnet fisheries, designed to allow recovered gear to be traced back to a particular state or fishery. However, entangling gear is often not recovered, and the ability to visually identify entangling gear in aerial surveys is limited by current gear marking practices. Here, I systematically evaluated aerial images of entangled whales to assess whether markings are visible and interpretable from the air. Across cases with sufficient visible line, regulatory color markings were only detectable in two of nine cases. Additionally, expert reviewers reached consensus on whether gear was marked in only half of the cases. These findings indicate that the current marking scheme does not allow aerial observers to consistently identify gear on a free-swimming entangled whale. I recommend incorporating fully colored, state-specific buoy lines, replacing limited segment based markings. This would provide a more robust means of identifying entangling gear, and support more accurate attribution of its sources to better inform management measures to reduce large whale entanglements. My findings highlight the importance of integrating real-world conditions into conservation tools to improve outcomes for critically endangered marine mammals.