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Mixed-stock apportionment of humpback whales from feeding grounds to breeding grounds in the North Pacific based on mtDNA
Kelly Lizewski, Debbie Steel, Karen Lohman, G. Renee Albertson, ?rsula Gonz?lez Peral, Jorge Urb?n R., John Calambokidis and C. Scott Baker
The allocation of catches from the feeding grounds to breeding stocks is one of the objectives of the Comprehensive Assessment of humpback whales in the North Pacific. This catch allocation is complicated by the mixing of individuals from different breeding stocks on shared feeding grounds. Here we use mixed-stock analyses to estimate the apportionment of humpback whales from feeding areas to breeding regions (i.e., source stocks), as a proxy for allocation of historical catches. For this, we first updated the frequencies of mitochondrial DNA haplotypes from regional samples collected during the program Structure of Populations, Levels of Abundance and Status of Humpback Whales (SPLASH) from 2004-2006, adding nearly 1,000 additional samples to the 1,800 published previously (Baker et al. 2013). Most of these additional samples were collected in Mexico, a region known to have a complex pattern of interchange and varying migratory destinations. We then used the Statistics Programme for Analyzing Mixtures (SPAM) to estimate the contributions of breeding regions to feeding areas based on six scenarios. These six scenarios allowed for revised stratification of both breeding regions and feeding areas, as previously defined by the program SPLASH. The preferred scenario considered apportioning each of the 6 feeding areas to 5 breeding regions, Asia (the Philippines, Okinawa and Ogasawara), Hawaii, offshore Mexico (Revillagigedo Islands), mainland Mexico and Central America.