Atlantic Sturgeon in the Ocumulgee River, GA
Although previous work on Atlantic Sturgeon (ATS) recruitment has provided important new baseline information regarding current recruitment rates in GA rivers, critical information gaps regarding the recovery status of these populations still remain because (1) historic information on population abundance for juveniles is completely lacking; and (2) quantified estimates of the adult runs have not been attempted for any system other than the Altamaha (Peterson et al. 2008). The unifying goal of the proposed project is to develop, evaluate, and implement a practical and reliable methodology for quantifying adult spawning runs of ATS in GA and other large coastal rivers. Specifically, we propose to use a combination of side-scan sonar and acoustic telemetry to quantify the annual spawning runs in the Altamaha River, GA. Secondary objectives will include the documentation, description, and mapping of specific spawning habitats in upper Altamaha system, including both the Oconee and Ocmulgee tributaries where putative spawning runs have only recently been identified (Ingram and Peterson, in press). The specific project objectives of this proposal are (1) to quantify annual spawning runs of ATS in the Upper Altamaha (including both major tributaries); (2) to document ATS spawning at specific sites and then, to describe key habitat conditions at those sites; and (3) Quantify annual recruitment of ATS in the Altamaha 18 months after each spawning run assessment to quantitatively examine the relationship between spawner abundance and annual recruitment; (4) to evaluate genetic structure of the adult spawners and the juvenile cohorts produced from those spawners, as a direct measure of the of variation in individual reproductive output within each spawning cycle. Completion of the proposed study objectives will specifically address 4 of the 7 research priorities identified in the NMFS Atlantic Sturgeon Status Review 2007.
Experimental Passage of Gulf sturgeon at Jim Woodruff Dam
Based on U.S. Fish and Wildlife data, an estimated 300-400 federally threatened Gulf sturgeon (Acipenser oxyrinchus desotoi) are currently located in the Apalachicola River (Florida) downstream of the Jim Woodruff Lock and Dam (JWLD). Limited suitable spawning habitat is available for Gulf sturgeon below JWLD, which currently impedes Gulf sturgeon upstream movements to historic spawning habitats in the Apalachicola-Chattahoochee-Flint (ACF) River Basin. Passage of Gulf sturgeon above JWLD could restore approximately 119 rkm of habitat in the Flint River and approximately 50 rkm of habitat in the Chattahoochee River. Passage of Gulf sturgeon above JWLD may allow for population growth and would limit the risks for catastrophic loss by allowing the population to be spread over a larger geographic area. Unfortunately, little is known about suitable (critical) spawning and nursery habitat areas in the ACF Basin and the potential ecological effects of restoring sturgeon to this river system. For example, recent findings indicate that restoration of Gulf sturgeon access to historic spawning habitat above JWLD may benefit imperiled native mussel populations.
In this study, we are using sonic telemetry to track pre- and post-spawn movements of wild Gulf sturgeon, captured below the dam and released upstream of JWLD. Immediately following their release above the Dam, the transferred fish are being continuously monitored using a combination of passive and active sonic tracking methods to identify and quantify potential spawning habitat in the Flint and Chattahoochee tributaries upstream of JWLD. Now that the spawning season has concluded, we are currently evaluating downstream passage of the same adults as they attempt to move through the locks at JWLD as they attempt to return to the Gulf of Mexico. The results of this project will provide critical baseline information regarding the future options for fish passage at JWLD.
Ecology and Recruitment of Juvenile Atlantic Sturgeon in Georgia
Throughout their range, Atlantic sturgeon populations have suffered declines resulting from decades of anthropogenic activities. Throughout much of 20th Century, adults were harvest during spring spawning migrations for both meat and caviar (Smith 1985). As northern stocks declined, commercial fishing shifted to southern rivers, particularly during the 1970s and 1980s (Colligan et al 1998). While overexploitation was likely a primary cause for population declines, habitat degradation may be impeding or limiting recovery of many populations (Smith 1985). Reduced water quality from introduced industrial effluents and poor land use practices have adversely affected both spawning and nursery habitats (Smith 1985, Colligan et al. 1998). Thermal effluents and pumping of ground water often degrades juvenile habitats by increasing water temperatures and lowering dissolved oxygen (Rochard et al. 1990, Collins et al. 2000, Niklitscheck and Secor 2005).
An understanding of recruitment mechanisms is a key element of assessing recovery for most Atlantic sturgeon populations. In the Hudson River for example, Peterson et al. (2000) estimated abundance of age-1 juveniles to demonstrate the severity of recruitment declines resulting from decades of overfishing. Unfortunately, studies of recruitment mechanisms in Atlantic sturgeon are rare, especially for southern populations. However, a recent study in the Suwannee River, Florida showed that annual recruitment in Gulf sturgeon (Acipenser desotoi), a subspecies of Atlantic sturgeon, can be significantly affected by mean river flows during September and December (Randall and Sulak 2007). Nonetheless, the stock-recruitment relationship for the species remains uncertain because abundance estimates for either juvenile or adults are lacking (Dadswell 2006, Peterson et al. 2008). Because quantified estimates of recruitment and recruitment mechanisms are needed to assess population recovery, the objectives of this study were to: 1) estimate annual age-specific abundance, 2) estimate annual apparent survival and per capita recruitment and 3) identify key factors that influence recruitment processes of juvenile Atlantic sturgeon in the Altamaha River, Georgia.
Assessment of the Atlantic Sturgeon and Shortnose Sturgeon populations in the Savannah River, Georgia
Throughout their ranges populations of Shortnose sturgeon and the Atlantic Sturgeon have suffered significant declines resulting from decades of anthropogenic activities. During much of 20th Century, adults of both species were harvest during spawning migrations in lucrative but short lived fisheries that stretched from the St. Lawrence River in Canada, to the St. Marys River in south Georgia. As northern stocks of both species declined, commercial fishing shifted to southern rivers, particularly during the 1970s and 1980s. Although overexploitation was likely a primary cause for population declines, habitat degradation may be impeding or limiting recovery of many populations. Reduced water quality from introduced industrial effluents and poor land use practices have adversely affected spawning and nursery habitats of both species throughout their ranges.
An understanding of recruitment mechanisms is a key element of assessing recovery for most Atlantic Sturgeon populations. In the Hudson River for example, Peterson et al. (2000) estimated abundance of age-1 juveniles to demonstrate the severity of recruitment declines resulting from decades of overfishing. Unfortunately, studies of recruitment mechanisms in Atlantic Sturgeon are rare, especially for southern populations. The primary purpose of this project is to obtain quantified assessment of Atlantic sturgeon and Shortnose sturgeon populations in Savannah River, Georgia. The first objective of the study is to estimate population abundance, and to evaluate the age structure of the current population of Shortnose Sturgeon. The second objective is to estimate recruitment of both Atlantic Sturgeon and Shorntnose Sturgeon. The final objective is to estimate annual run size and age structure of the adult Atlantic sturgeon population. Quantified estimates of these basic population parameters will provide a baseline assessment of the current populations of both species within the Savannah River. The basic methodology used will be similar to those used in the author’s previous sturgeon studies in several other Georgia Rivers, including the Altamaha, Ogeechee, Satilla, and St. Marys. Field work will focus on the intensive mark-recapture sampling of both species using a combination of gill nets and trammel nets to obtain quantified estimates of population size, age structure, recruitment. Results from this study will provide baseline population data for future population monitoring of both species within the Savannah system.