Can baleen whales be safely live-captured for studies of their physiology?

Abstract

Studying baleen whales is challenging and complex, where observation of their habitat, sensory modalities, behavior and physiology, are infrequent and brief. The biochemical and biophysical contribution of mysticetes serve a vital role in maintaining a healthy marine ecosystem, but they are facing anthropogenic threats. Before giving any indications of how these threats affect the baleen whales, it is essential to gain more knowledge of their sensory physiology, migration patterns, and energy expenditure. Previous research on mysticetes has been based on post-mortem investigation, modeling, behavioral analyses, and tagging which are advancing with time. However, some of these studies may need validation, which could be conducted with a mysticete live-capture methodology. This thesis describes an approach on how to possibly live-capture baleen whales to enable safe studies of their physiology. Therefore, my objectives aimed to 1) assess the methodology of live-capturing and restraining baleen whales by reviewing and evaluating documented attempts and those gained in own fieldwork, 2) discuss what sensory modalities baleen whales may use to navigate around nets in such settings. Furthermore, 3) I have reviewed potential studies that could be conducted on a restrained mysticete, and lastly 4) I discuss animal welfare considerations of mysticete live-capture and experimental studies. A large entrapment was created in Vestfjord, Norway, June 2021. Attempts were made to measure the distance of the baleen whales from the various nets that were designed to be better detected by different sensory methods, including recording hydrophones placed in the entrapment. These results did not give enough statistical power for concluding what sensory apparatus the cetaceans may use in detecting the entrapment set-up. We did succeed in leading baleen whales in between islets and trap them there with nets, but were unable to restrain any of them for direct measurements. The 4-year ongoing SOST minke hearing project has potential to succeed though, and may thereby represent a key to a more detailed insight into the physiology of these huge but vulnerable creatures.