Preliminary Observations of Population Genetics and Relatedness of the Broadnose Sevengill Shark, Notorynchus cepedianus, in Two Northeast Pacific Estuaries.

The broadnose sevengill shark, Notorynchus cepedianus, a common coastal species in the eastern North Pacific, was sampled during routine capture and tagging operations conducted from 2005-2012. One hundred and thirty three biopsy samples were taken during these research operations in Willapa Bay, Washington and in San Francisco Bay, California. Genotypic data from seven polymorphic microsatellites (derived from the related sixgill shark, Hexanchus griseus) were used to describe N. cepedianus genetic diversity, population structure and relatedness. Diversity within N. cepedianus was found to be low to moderate with an average observed heterozygosity of 0.41, expected heterozygosity of 0.53, and an average of 5.1 alleles per microsatellite locus. There was no evidence of a recent population bottleneck based on genetic data. Analyses of genetic differences between the two sampled estuaries suggest two distinct populations with some genetic mixing of sharks sampled during 2005-2006. Relatedness within sampled populations was high, with percent relatedness among sharks caught in the same area indicating 42.30% first-order relative relationships (full or half siblings). Estuary-specific familial relationships suggest that management of N. cepedianus on the U.S. West Coast should incorporate stock-specific management goals to conserve this ecologically important predator

A: Principal Coordinates Analysis of Sevengill sharks.

<p>Axis 1 and 2 explaining 56% of the variation. Note WA and SF-2 clearly separated but WA and SF-1 intermixing which is likely due to some shared common ancestry. B: Population assignment of sevengill shark using cluster analysis. Note WA separating from the two SF groups.</p

Allelic patterns and diversity among measured sevengill populations.

<p>NA = Average number of alleles and He = expected heterozygosity.</p

Percentage relatedness (1 = 100%) within and between sevengill shark populations.

<p>FS: Full sibling, HS: Half sibling, and U: Unrelated. The values from COLONY were significantly different from COANCESTRY and MLRELATE at the p = 0.05 level for related individuals within and between populations. The values of within vs between relatedness found in all three programs were significant at the p = 0.0001 level (paired t tests).</p><p>Percentage relatedness (1 = 100%) within and between sevengill shark populations.</p