Entanglement in fishing gear is a known source of large whale injury and mortality. Although management initiatives are being implemented to reduce impacts, their effectiveness is difficult to evaluate from eye-witnessed entanglements alone. Furthermore, entanglement rates and impacts are not well-understood in most areas of the world. Our research focusses on the frequency of entanglement, the nature of these events and their impacts on individuals and populations. The data that CCS staff collect during disentanglement efforts have been essential to understanding this problem. See below for some of our scientific publications and technical reports on this important issue.
Since 1997, CCS has studied injuries on free-ranging humpback whales as an alternate way of tracking entanglement rates. We developed systematic protocols for data collection and our methods of scar interpretation have been modeled on and successfully tested with eyewitnessed entanglement events. This research indicates that more than half of the humpback whales in the Gulf of Maine exhibit scarring that was likely to have resulted from a prior entanglement. Scar acquisition rates indicate that an average of 12% of the population becomes entangled annually. Juveniles appear to be at highest risk, although whales continue to become entangled when mature. Fewer than 10% of the whales that acquire new entanglement injuries were actually seen and reported while entangled.
Entanglement is a more frequent occurrence than observed cases would suggest. The most effective management initiatives are therefore those that focus on prevention, rather than intervention for witnessed events. Nevertheless, disentanglement can improve the outcome for individuals that are witnessed entangled and generates critical data for understanding and thereby preventing future events. Learn more about our disentanglement efforts here.
Selected CCS publications and technical reports on the entanglement issue: