The status of humpback whale populations under the US Endangered Species Act (ESA) was changed recently to remove the species-level listing of endangered and recognize 14 Distinct Population Segments (DPS), each with a distinct ESA status. For the four DPSs in the North Pacific, one (Hawaii) was not listed, one (Mexico) was listed as threatened, and two (Central America and W North Pacific) remain as endangered. Although DPSs are based on their breeding population regions, humpbacks spend most of their time on feeding areas where they show strong fidelity and where most human impacts occur. Therefore, management actions are critical on feeding areas and should be integrated appropriately with the DPS designations. This is important for the US West Coast where humpback whales from the Mexican and Central American DPSs intermix and where fisheries entanglements have increased dramatically since 2015. We examine interchange rates of humpback whales from the US West Coast to different DPSs using both an integrated geographically stratified model based on the 2004-2006 SPLASH data and finer-scale, more up-to-date photo-identification data, and mtDNA haplotype patterns. They indicate: 1) the US West Coast is the migratory destination for the entire Central America Endangered DPS; 2) the proportion of animals going to Central America and Mexico varies not only by the larger feeding areas where they have been recognized but also among finer scale subareas; 3) the highest proportion of whales from the Endangered Central America DPS occur off Southern California and 4) the delineation of the Mexican and Central American DPSs requires further investigation given that humpback whales from southern Mexico share more in common with Central America than those from the principal Mexican breeding regions. These results have implications for allocating anthropogenic mortality to DPSs and comparing mortality to Potential Biological Removal limits under the US MMPA.
Steiger, G., J Calambokidis, P. Wade, K. Audley, C. S. Baker. 2017. Migratory destinations of humpback whales that feed along the US West Coast: Implications for management under the newly recognized Distinct Population Segments. Abstract (Proceedings) 22nd Biennial on the Biology of Marine Mammals, Halifax, Nova Scotia, October 22-27, 2017.