Assessment of population structure in Pacific Lepeophtheirus salmonis (Kroyer) using single nucleotide polymorphism and microsatellite genetic markers

The ectoparasitic sea louse. Lepeophtheirus salmonis (Kroyer), has caused great concern for both wild salmon fisheries and the salmon aquaculture industry. Identifying the population structure of this parasite is important for better understanding its dispersal capabilities and controlling louse infections. Most of the sea lice population studies carried out to date have been focused on Atlantic Ocean L. salmonis where host parasite interactions may be quite different than those in the Pacific Ocean. In this study we examined the genetic population structure of sea lice from 12 Pacific Ocean samples ranging from the Bering Sea to southern Vancouver Island using 27 microsatellite and 87 single nucleotide polymorphisms (SNPs) from 25 loci. Louse samples were analyzed for genetic differentiation among farmed and wild host salmon in addition to temporal differentiation from 2007 to 2009 and spatial differentiation over the entire sampling range. Our analyses failed to resolve significant population structure in L. salmonis for any of these three comparisons. Our results therefore support a hypothesis of high migration and panmixis of L. salmonis within the studied area of the Pacific Ocean. (C) 2010 Elsevier B.V. All rights reserved.