Abstract
To reduce or eliminate the problem of right whale entanglements in fishing gear, scientists and gear developers have considered the feasibility of enhancing ropes and nets to improve their detection by whales. We conducted laboratory studies which showed that right whale visual sensitivity is tuned to perceive red and orange as high contrast “black” against the ambient blue/green oceanic background light. To determine whether changing the color of the ropes alters the distance at which whales can detect them, we conducted field trials in Cape Cod Bay in the spring of 2013. Rope-mimics were placed in front of right whales that were skim-feeding at the surface, so that changes in behavior (respiration, mouth closures, submergence times, and turning angles) and the distance of that change from the rope mimic (distance of detection) could be documented. Rope mimics were made from rigid PVC pipe, weighted at one end, and attached to a float at the other end, so each whale encountered the equivalent of a vertical buoy line as it swam near the surface. Color selection for the rope mimics included black, green, red, and orange (the first two mimic existing fishing rope colors). A total of 101 encounters between whales and the rope mimics were documented, and analysis indicates that red and orange colored rope mimics were detected by right whales at significantly greater distances than green ones. This suggests that changing commercial fishing rope color to red and/or orange may enhance the whale’s ability to visually avoid entanglements in the wild. Field trials of orange ropes by a group of Maine lobstermen indicate that switching rope colors in that industry is feasible.