Conservation genetics of North American green sturgeon: Advances for precautionary management and population monitoring

North American green sturgeon (Acipenser medirostris ) are highly migratory, iteroparous, highly fecund, and demonstrate late sexual maturity and wide physiological tolerances to survive stochastic natural changes associated with the environments they utilize for reproduction and foraging. These same characteristics make green sturgeon vulnerable to contemporary stressors like loss of spawning habitat and overfishing. Basic biological information about green sturgeon is limited, and the genetic studies presented in this dissertation provide information about population structure, distribution of management units, reproductive behavior and important biological characteristics of the species. Traditional measurements of genetic differentiation and genetic distance, as well as tests of assignment and ancestry supported separating the species into two population segments. Following a petition to list green sturgeon under the Endangered Species Act, the National Marine Fisheries Service's status review delineated the Sacramento River as the sole reproducing population in the Southern Distinct Population Segment (DPS), while the Rogue and Klamath rivers were identified as containing a distinct population, recognizable as the Northern DPS. Sample collections from natal rivers were evaluated for use in genetic stock identification and a variety of analytical approaches demonstrated the power of this baseline for identifying green sturgeon of unknown natal origin. These data were applied to address concerns about the presence of Southern DPS green sturgeon in Northern DPS estuaries. A significant proportion of green sturgeon in the Columbia River and Willapa Bay appeared to originate from the Sacramento River, while a collection of fish from Grays Harbor was almost equally split from the Southern and Northern DPSs. An evaluation of relatedness among wild green sturgeon fry was completed to estimate the number of full-sibling green sturgeon kin groups. Using kin group partitioning and accumulation functions, an estimated 5.1 to 26.7 families were produced in the Upper Sacramento River annually between 2002 and 2006. A positive correlation between the estimated abundance of families and the monthly average river flow was detected. These studies provide a foundation to support precautionary management and population monitoring of green sturgeon at both the river and regional landscape scale.