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Allozymes are less polymorphic than microsatellites, and may thus fail to detect structure in large populations.Nonetheless, microsatellite-based studies of snow crab populations in northeastern Canada also failed to detect significant population structure over similar spatial scales (Puebla et al., 2008).In addition, changing temperatures appear to be driving a northward range contraction in the Pacific-Arctic region (Dionne et al., 2003; Orensanz et al., 2004), as evidenced by substantial increases in snow-crab biomass and abundance in the Chukchi Sea since the 1970s (Bluhm et al., 2009).

This discovery was significant because a latitudinal cline in size-at-maturity has been well-documented in both Pacific and Atlantic populations, with morphometrically mature Chukchi Sea snow crabs typically only reaching 40 to CW (Somerton, 1981; Burmeister and Sainte-Marie, 2010).Harvest increased during the 1980s as catches of the more valuable Tanner crab, Rathbun, 1924, began to decline (Bowers et al., 2008).Since that time, EBS stocks have undergone large inter-annual fluctuations in population size, and were declared overfished in 1999 (NPFMC, 2010). Station BFP (inset) in the Beaufort Sea is comprised of samples pooled from sites 2, 4, 22, 23, 24 and 26 (site numbers correspond to Rand and Logerwell, 2011).Decreasing sea ice in the Arctic is expected to impact marine ecosystems, and to lead to increased human activity in the form of shipping traffic, fishing pressure, and mineral resource exploration and extraction.In the face of these pressures, we examine genetic population structure in the snow crab (Fabricius, 1788), throughout its distribution in Alaskan waters, to determine degrees of population connectivity between the Arctic and more southerly portions of the species’ range.Idealized oceanographic flow through the study area (based on Stabeno et al., 2001; Weingartner et al., 2005; Parada et al., 2010) shown by black arrows.Site 7 (BF7) was not pooled due to the presence of larger-sized individuals at this site.Changing climate in the Arctic is manifesting as warming temperatures and changing sea ice conditions, with consequences for marine communities (Grebmeier, 2012).Moreover, declining sea ice coverage is opening up areas of the Arctic shelves to increased human presence in the form of shipping traffic and petroleum resource extraction activities, and stimulating interest in potential exploitation of new fisheries resources.Relatively little attention has been paid to snow crab stocks in the Chukchi and Beaufort Seas, where large aggregations also occur (Paul et al., 1997; Bluhm et al., 2009; Rand and Logerwell, 2011).These unexplored populations may be sources or sinks for genetic exchange with other, more intensively fished populations farther south, or farther east in Canadian waters.