Effectiveness of mitigation measures to reduce interactions between commercial fishing gear and whales

The authors investigated several data sources and conducted surveys to identify potential mitigation measures that could be used to reduce humpback whale entanglements in Western Australia (WA). The Cetacean Stranding Database (CSD) and Commercial Whale Watching Database (CWWD), managed by the Western Australia Department of Parks and Wildlife, were both investigated. High occurrences of whale entanglements off the central coast of WA were identified in the CSD.  Commercial fishing records combined with entanglement records indicated that entangled whales mostly move contrary to movement patterns of the general population. Suggesting the high entanglement rates off the central coast may be reflective of southern and eastern movements of entangled whales during their northward migration. The CWWD database indicated changes in the timing of whale migrations. Updates to logbooks were also made during this study. Paper based logbooks were updated to smart-phone applications. Spatial models indicated that depth ranges of 4-40 ma nd distance from the coast (5-21 m) are useful in predicting the occurrence of humpback whales. An industry lead workshop identified potential whale entanglement mitigation measures, all of which were trialed by fishers after the workshop. All mitigation measures tested, except for remote releases, showed a trade off between price and practicality. Based on these results, rope type, rope length and number of floats used were tested industry wide during trials. This project examined the use of acoustic pingers and found their use made no difference to the behavior of humpback whales. An assessment of their effectiveness was not conducted during this study. Other results from this study indicated, preliminarily, that whales are more likely to become entangled in thinner ropes, and mainlines that are yellow or orange.