Genetic Structure and Patterns of Annual Genetic Diversity Among Collections of Longfin Smelt in the San Francisco Bay-Delta

The demographic independence of the longfin smelt (Spirinchus thaleichthys) population inhabiting the San Francisco Bay-Delta is unknown, yet it may be geographically isolated from populations occurring further north along the Pacific Coast. Longfin smelt are an anadromous fish inhabiting estuarine and nearshore marine waters along the western Pacific coast and there exists potential for them to migrate between coastal populations. Genetic information can provide insight into the gene flow between fish from different locations, and the spatial and temporal scales at which longfin smelt collections are differentiated is a critical uncertainty that influences how the species is managed.  We developed seventeen microsatellite DNA loci to assess genetic diversity within and among longfin samples from the west coast. In a preliminary screen of these collections, 5 to 16 alleles per locus were detected, the expected heterozygosity ranged from 0.33-0.93, and moderate levels of differentiation were found. Additionally, we characterized patterns of annual genetic diversity among longfin smelt collections from a variety of Bay-Delta fish monitoring programs. Results from broader temporal samples will be discussed in this presentation to determine the population structure of longfin smelt, and an update about sample collection for other Pacific Northwest locations will be given.  The diversity observed in these collections suggests management of longfin smelt may increase the sustainability of the population by focusing on segments of the species scaled relevant to natal estuaries along the west coast.