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The shortnose sturgeon Acipenser brevirostrum is one of the most endangered members of the sturgeon family because of overexploitation, depressed population levels, and a shrinking range. The lack of historical data on shortnose sturgeon populations has led to an increase in sturgeon research over the last three decades; however, most recent studies have not focused on southern populations. The objective of this study was to estimate the abundance, annual survival, and temporary emigration rates of shortnose sturgeon in the Ogeechee River, Georgia. Shortnose sturgeon were captured with gill and trammel nets for a mark–recapture analysis from 1 June to 31 August in each of the 3 years from 2007 to 2009. Over the three summers of sampling, we conducted a total of 864 net sets and captured 168 individual shortnose sturgeon with an additional 51 recaptures. Our analysis revealed that the best‐fitting robust design population models incorporated interactions among water temperature, dissolved oxygen, and total effort in which capture and recapture probabilities were set equal and temporary emigration parameters were set to zero or held constant. Abundance estimates (95% confidence interval [CI]) were 404 (175–633), 264 (126–402), and 203 (32–446) individual sturgeon for 2007, 2008, and 2009, respectively. Population parameter estimates of annual survival and temporary emigration, combined with documented emigration and immigration of tagged individuals to and from the adjacent Altamaha River, provided evidence that the Ogeechee River stock is not discrete but possibly a metapopulation with the Altamaha River.

Fishes require a variety of habitats to meet life-history requirements over their lifespan, and reproductive microhabitat requirements are particularly important because spawning sets the context for all other life stages (Balon, 1975;Schlosser, 1991). Understanding spawning microhabitat use of fishes allows for the prediction of population-level

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Southern populations of the federally endangered Shortnose Sturgeon Acipenser brevirostrum are considered to be at greater risk of extirpation than northern populations. Our study focused on the Ogeechee River, Georgia, a small, undeveloped, coastal river that supports a population with fewer than 300 Shortnose Sturgeon. We designed a population viability analysis (PVA) model to represent and quantify the demographic influences of three factors (poor water quality, intrusion of saline water via rice canals, and incidental harvest) on the viability of this population. As an isolated population, only 75% of simulated populations persisted beyond a 20‐year time horizon with all factors simulated. However, immigration from the Altamaha River may help to support the population. We quantified population persistence with and without simulating each factor and found that (1) incidental harvest had no effect on simulated persistence, (2) poor water quality decreased simulated persistence by 29%, primarily due to low oxygen conditions in summer, and (3) roughly one‐third of this effect was attributed to rice canals (premature exposure of juveniles to high salinities). Simulated recruitment to age 1 was limited by a habitat squeeze between density‐dependent starvation upstream near the spawning grounds and premature exposure to salinity downstream. These results highlight a need for research on availability of summer refuge and freshwater rearing habitat. As these results derived from a PVA model, which required many assumptions, they should be considered preliminary. Further field research is needed to confirm those results where it is possible to test intermediate predictions. We conclude by suggesting that efforts to maintain or increase the number of viable populations of Shortnose Sturgeon in southern U.S. rivers will probably require an understanding of (1) source‐sink dynamics between populations in rivers with access to adequate freshwater rearing habitat and those without, and (2) the effects of climate change.

Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus, Acipenseridae) populations are currently at severely depleted levels due to historic overfishing, habitat loss, and pollution. The importance of biologically correct stock structure for effective conservation and management efforts is well known. Recent improvements in our understanding of Atlantic sturgeon migrations, movement, and the occurrence of putative dual spawning groups leads to questions regarding the true stock structure of this endangered species. In the James River, VA specifically, captures of spawning Atlantic sturgeon and accompanying telemetry data suggest there are two discrete spawning groups of Atlantic sturgeon. The two putative spawning groups were genetically evaluated using a powerful microsatellite marker suite to determine if they are genetically distinct. Specifically, this study evaluates the genetic structure, characterizes the genetic diversity, estimates effective population size, and measures inbreeding of Atlantic sturgeon in the James River. The results indicate that fall and spring spawning James River Atlantic sturgeon groups are genetically distinct (overall FST = 0.048, F’ST = 0.181) with little admixture between the groups. The observed levels of genetic diversity and effective population sizes along with the lack of detected inbreeding all indicated that the James River has two genetically healthy populations of Atlantic sturgeon. The study also demonstrates that samples from adult Atlantic sturgeon, with proper sample selection criteria, can be informative when creating reference population databases. The presence of two genetically-distinct spawning groups of Atlantic sturgeon within the James River raises concerns about the current genetic assignment used by managers. Other nearby rivers may also have dual spawning groups that either are not accounted for or are pooled in reference databases. Our results represent the second documentation of genetically distinct dual spawning groups of Atlantic sturgeon in river systems along the U.S. Atlantic coast, suggesting that current reference population database should be updated to incorporate both new samples and our increased understanding of Atlantic sturgeon life history.

Bartram's Bass" Micropterus sp. cf. coosae is endemic to the upper Savannah River basin of the southeastern United States and is threatened by hybridization with invasive Alabama Bass Micropterus henshalli. Bartram's Bass have been functionally extirpated from reservoirs, and hybrid individuals have been detected in several tributaries. However, the extent of introgression in tributaries is currently unknown. Our objectives were to (1) assess the distribution of Bartram's Bass, native Largemouth Bass M. salmoides, invasive Alabama Bass, and their hybrids in streams of the upper Savannah River basin and (2) quantify effects of abiotic variables on the distribution of each species. We sampled 154 locations in 2017 and 2018 and assigned genetic identity using hydrolysis probes and microsatellites. We used conditional inference trees to quantify variables affecting the occurrence of each species and hybrids. We observed widespread hybridization across the basin. Pure Bartram's Bass were collected at 27% (42) of sites, among which only 12 sites contained pure Bartram's Bass and no other congeners. Thirty sites where pure Bartram's Bass were collected contained hybrids. In the montane Blue Ridge ecoregion, occurrence of pure Bartram's Bass was negatively affected by low levels of local-scale developed land cover. In the lower-relief Piedmont ecoregion, pure Bartram's Bass were positively associated with watershed-scale forest land cover and stream gradient. Distance from a reservoir was positively associated with occurrence of pure Bartram's Bass in both ecoregions. Pure Bartram's Bass are likely to occur with high probability in only 16% of nonimpounded stream segments; this represents a conservative estimate, and the true number is likely lower. However, future work

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