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Atlantic Sturgeon Acipenser oxyrinchus, a federally endangered anadromous fish, persist along the East Coast of North America. Despite two decades of federal protection, many populations have yet to fully recover and major knowledge gaps remain, especially in the southern portion of the species’ range. The seasonal movement patterns of river‐resident juveniles (RRJs) are not well understood, and little is known about the transition from the RRJlife stage to the marine‐migratory juvenile (MMJ) life stage. During the summers of 2014–2016 we captured and acoustically tagged age‐1 RRJAtlantic Sturgeon in the Ogeechee, Altamaha, and Satilla rivers, Georgia, to (1) describe and quantify seasonal movements of RRJAtlantic Sturgeon in order to identify important estuarine nursery areas and (2) examined temporal patterns of out‐migration in order to better understand the critical transition from RRJto MMJin Georgia rivers. Movements of 79 fish were monitored using an array of stationary receivers deployed downstream from the heads of tide in each river system. During the summer months in each river, the fish congregated in upriver, freshwater reaches, but during the winter months they moved downriver and became more broadly distributed. Some fish (36.7%; n =29) migrated back up their natal river in the spring and remained there as age‐2 RRJs. We observed the out‐migration of 30.4% (n =24) of age‐2 MMJs only during December–March, based on detections outside their natal river. The results of this study support the assumption of the closure of age‐1 populations that underpins recent quantitative studies of Atlantic Sturgeon recruitment.

Endemic to the Apalachicola River basin of the southeastern USA, the Shoal Bass Micropterus cataractaeis a fluvial‐specialist sport fish that is imperiled because of anthropogenic habitat alteration. To counter population declines, restorative stocking efforts are becoming an increasingly relevant management strategy. However, population genetic structure within the species is currently unknown, but it could influence management decisions, such as brood source location. Leveraging a collaborative effort to collect and genotype specimens with 16 microsatellite loci, our objective was to characterize hierarchical population structure and genetic differentiation of the Shoal Bass across its native range, including an examination of structuring mechanisms, such as relatedness and inbreeding levels. Specimens identified as Shoal Bass were collected from 13 distinct sites (Nranged from 17 to 209 per location) and were then taxonomically screened to remove nonnative congeners and hybrids (pure Shoal Bass Nranged from 13 to 183 per location). Our results revealed appreciable population structure, with five distinct Shoal Bass populations identifiable at the uppermost hierarchical level that generally corresponded with natural geographic features and anthropogenic barriers. Substructure was recovered within several of these populations, wherein differences appeared related to spatial isolation and local population dynamics. An analysis of molecular variance revealed that 3.6% of the variation in our data set was accounted for among three larger river drainages, but substructure within each river drainage also explained an additional 8.9% of genetic variation, demonstrating that management at a scale lower than the river drainage level would likely best conserve genetic diversity. Results provide a population genetic framework that can inform future management decisions, such as brood source location, so that genetic diversity within and among populations is conserved and overall adaptability of the species is maintained.

AbstractThe federally endangered Shortnose Sturgeon Acipenser brevirostrumwas once abundant in all major coastal river systems from the Saint John River, Canada, to the St. Johns River, Florida. During much of the 20th century, however, populations suffered major declines throughout their range from the combined effects of overfishing, pollution, and habitat loss. Although the species was a charter member of the Endangered Species Act, quantified population assessments are still lacking for many river systems throughout their range. Because river-specific assessments are critical for evaluating species recovery, the objective of this study was to quantify abundance and annual recruitment of Shortnose Sturgeon occupying the Savannah River, Georgia. Anchored gill nets and trammel nets fished during slack tides were used to sample juvenile and adult Shortnose Sturgeon in their summer holding areas during 2013–2015. Huggins closed-capture models in RMark were used to derive abundance estimates for each demographic group. The best models estimated that the Savannah River contained 81 (95% CI = 27–264) age-1 juveniles in 2013, 270 (162–468) in 2014, and 245 (104–691) in 2015. The models also estimated the river to contain 486 (198–1,273) age-2+ juveniles in 2013, 123 (69–235) in 2014, and 187 (81–526) in 2015. Similarly, the adult population was estimated to be 1,865 (784–4,694) individuals in 2013, 1,564 (1,005–2,513) in 2014, and 940 (535–1,753) in 2015. The results of this study provide the first population estimates available for Shortnose Sturgeon in the Savannah River. Additionally, the results suggest that the Savannah River likely contains the second largest population of Shortnose Sturgeon in Georgia. Future studies are needed in the Savannah River and other South Atlantic river systems to better evaluate Shortnose Sturgeon recovery status and the effects of river-specific anthropogenic modifications.Received June 27, 2016; accepted September 29, 2016 Published online December 2, 2016

The federally endangered Shortnose Sturgeon Acipenser brevirostrumwas once abundant in all major coastal river systems from the Saint John River, Canada, to the St. Johns River, Florida. During much of the 20th century, however, populations suffered major declines throughout their range from the combined effects of overfishing, pollution, and habitat loss. Although the species was a charter member of the Endangered Species Act, quantified population assessments are still lacking for many river systems throughout their range. Because river-specific assessments are critical for evaluating species recovery, the objective of this study was to quantify abundance and annual recruitment of Shortnose Sturgeon occupying the Savannah River, Georgia. Anchored gill nets and trammel nets fished during slack tides were used to sample juvenile and adult Shortnose Sturgeon in their summer holding areas during 2013–2015. Huggins closed-capture models in RMark were used to derive abundance estimates for each demographic group. The best models estimated that the Savannah River contained 81 (95% CI = 27–264) age-1 juveniles in 2013, 270 (162–468) in 2014, and 245 (104–691) in 2015. The models also estimated the river to contain 486 (198–1,273) age-2+ juveniles in 2013, 123 (69–235) in 2014, and 187 (81–526) in 2015. Similarly, the adult population was estimated to be 1,865 (784–4,694) individuals in 2013, 1,564 (1,005–2,513) in 2014, and 940 (535–1,753) in 2015. The results of this study provide the first population estimates available for Shortnose Sturgeon in the Savannah River. Additionally, the results suggest that the Savannah River likely contains the second largest population of Shortnose Sturgeon in Georgia. Future studies are needed in the Savannah River and other South Atlantic river systems to better evaluate Shortnose Sturgeon recovery status and the effects of river-specific anthropogenic modifications. Received June 27, 2016; accepted September 29, 2016 Published online December 2, 2016

AbstractAtlantic Sturgeon Acipenser oxyrinchus oxyrinchuswere once abundant along the Atlantic coast of North America from the Saint Lawrence River, Canada, to the St. Johns River, Florida. Severe overfishing, coupled with habitat losses during the 1900s, resulted in major population declines that eventually led to the subspecies’ listing under the U.S. Endangered Species Act in 2012. Despite this listing, quantified recruitment data are largely lacking for most Atlantic Sturgeon populations, particularly those within the South Atlantic distinct population segment. The objective of this study was to quantify annual recruitment of Atlantic Sturgeon in the Savannah River, Georgia, by estimating annual abundance of age-1, river-resident juveniles. During the summers of 2013–2015, we used anchored gill nets and trammel nets to sample juvenile Atlantic Sturgeon throughout the Savannah River estuary. Ages of captured juveniles were determined by using length-frequency analysis, and abundance of each juvenile age-class was estimated with Huggins closed-capture models in RMark. We estimated the Savannah River to contain 528 age-1 juveniles in 2013, 589 in 2014, and 597 in 2015. The results from this study indicate that the Savannah River population is likely the second largest within the South Atlantic distinct population segment. Future studies are needed to determine the relative importance of the Savannah River as a natural source of recruitment for smaller, more imperiled populations in adjacent rivers. Consequently, we suggest that management efforts continue to prioritize the protection of both the population and the associated critical habitats within the Savannah River estuary.Received April 7, 2016; accepted June 28, 2016 Published online September 23, 2016

Atlantic Sturgeon Acipenser oxyrinchus oxyrinchuswere once abundant along the Atlantic coast of North America from the Saint Lawrence River, Canada, to the St. Johns River, Florida. Severe overfishing, coupled with habitat losses during the 1900s, resulted in major population declines that eventually led to the subspecies’ listing under the U.S. Endangered Species Act in 2012. Despite this listing, quantified recruitment data are largely lacking for most Atlantic Sturgeon populations, particularly those within the South Atlantic distinct population segment. The objective of this study was to quantify annual recruitment of Atlantic Sturgeon in the Savannah River, Georgia, by estimating annual abundance of age-1, river-resident juveniles. During the summers of 2013–2015, we used anchored gill nets and trammel nets to sample juvenile Atlantic Sturgeon throughout the Savannah River estuary. Ages of captured juveniles were determined by using length-frequency analysis, and abundance of each juvenile age-class was estimated with Huggins closed-capture models in RMark. We estimated the Savannah River to contain 528 age-1 juveniles in 2013, 589 in 2014, and 597 in 2015. The results from this study indicate that the Savannah River population is likely the second largest within the South Atlantic distinct population segment. Future studies are needed to determine the relative importance of the Savannah River as a natural source of recruitment for smaller, more imperiled populations in adjacent rivers. Consequently, we suggest that management efforts continue to prioritize the protection of both the population and the associated critical habitats within the Savannah River estuary. Received April 7, 2016; accepted June 28, 2016 Published online September 23, 2016

AbstractThe Atlantic Sturgeon Acipenser oxyrinchus oxyrinchusis an important component of biodiversity along the Atlantic coast of North America, but most populations have been decimated by habitat degradation and chronic overfishing. Historically, spawning populations existed in all major Atlantic coast rivers from the St. Lawrence River, Quebec, to the St. Johns River, Florida, but fisheries surveys conducted in the past two decades suggest that several populations at the southern extent of this range are now extirpated or have declined to remnant status. Our objective was to assess the abundance and genetic character of Atlantic Sturgeon in the Satilla River, Georgia. Using entanglement gears, we expended over 2,800 h of sampling effort and captured a total of 193 Atlantic Sturgeon in tidally influenced reaches of the river during 2008–2010. Of the 157 fish that were collected in 2010, 72 were identified as river-resident juveniles (ages 0–1). Genetic analyses of a subset (n= 61) of these juveniles revealed (1) depauperate levels of mitochondrial DNA (mtDNA) haplotype diversity and (2) the presence of large family units based on microsatellite DNA multilocus genotypes, collectively suggesting that very few parents produced the 2008 year-class. The mtDNA and microsatellite analyses both indicated that juveniles in the Satilla River population were genetically distinct from other populations in the South Atlantic Distinct Population Segment. Atlantic Sturgeon life history characteristics and the present results suggest that sampled juveniles from the 2008 year-class were the offspring of a small remnant pool of Satilla River adults; however, a full description of the population's genetic character and origin will require additional juvenile samples from future year-classes.Received May 15, 2015; accepted September 9, 2015

The Atlantic Sturgeon Acipenser oxyrinchus oxyrinchusis an important component of biodiversity along the Atlantic coast of North America, but most populations have been decimated by habitat degradation and chronic overfishing. Historically, spawning populations existed in all major Atlantic coast rivers from the St. Lawrence River, Quebec, to the St. Johns River, Florida, but fisheries surveys conducted in the past two decades suggest that several populations at the southern extent of this range are now extirpated or have declined to remnant status. Our objective was to assess the abundance and genetic character of Atlantic Sturgeon in the Satilla River, Georgia. Using entanglement gears, we expended over 2,800 h of sampling effort and captured a total of 193 Atlantic Sturgeon in tidally influenced reaches of the river during 2008–2010. Of the 157 fish that were collected in 2010, 72 were identified as river-resident juveniles (ages 0–1). Genetic analyses of a subset (n= 61) of these juveniles revealed (1) depauperate levels of mitochondrial DNA (mtDNA) haplotype diversity and (2) the presence of large family units based on microsatellite DNA multilocus genotypes, collectively suggesting that very few parents produced the 2008 year-class. The mtDNA and microsatellite analyses both indicated that juveniles in the Satilla River population were genetically distinct from other populations in the South Atlantic Distinct Population Segment. Atlantic Sturgeon life history characteristics and the present results suggest that sampled juveniles from the 2008 year-class were the offspring of a small remnant pool of Satilla River adults; however, a full description of the population's genetic character and origin will require additional juvenile samples from future year-classes.

Intracoelomic transmitters are commonly used to evaluate migratory patterns, distribution, and habitat use of many species of fish. Currently, transmitter implantation relies mostly on the assumption that transmitters do not cause any adverse physiological or pathological effects on the animal. To investigate these effects, we surgically implanted 60 Siberian Sturgeon Acipenser baeriwith transmitters that weighed less than 2% of their body weight. Postoperative assessments were conducted at 1, 2, 8, 12, 26, and 55 weeks to evaluate surgical healing and transmitter retention. Blood samples were collected before and after the 55-week study for serum cortisol analysis. Overall transmitter loss was 32%. Minor to moderate adhesions were noted at necropsy but did not appear to affect organ function. One fish was noted to have an intraintestinal transmitter at necropsy, but the fish was in overall good health. Long-term transmitter presence does not appear to increase serum cortisol levels or affect overall growth more than nontransmitter fish. Although long-term telemetry studies can be undertaken with minimal concern for negative physiological or pathological effects from transmitters, researchers should be aware that transmitter loss rates may be higher than previously thought. Mechanisms for transmitter loss may include expulsion through the surgical incision, expulsion through the mucocutaneous junction between the large intestine and the vent, or intraintestinal capture and expulsion through the vent. Received February 10, 2013; accepted June 10, 2013

Endangered Shortnose Sturgeon Acipenser brevirostruminhabit large tidal rivers along the Atlantic coastline of North America, ranging from the St. John River, Canada, southward to the St. Johns River, Florida. Currently, long-term assessments of the abundance and age structure of southern populations are completely lacking. To address this information gap, we assessed recent changes in Shortnose Sturgeon abundance and age structure by sampling with anchored entanglement gear in the Altamaha River, Georgia, during summer in 2004–2010. To estimate abundance, we used the Huggins closed-capture model in Program MARK. We assessed size structure by interpreting the first, second, and third quartiles of the FL of individuals captured during each year. In total, we captured 1,737 Shortnose Sturgeon (72 recaptures). Total estimated abundance was variable, ranging from 1,206 individuals (95% lognormal confidence interval [CI] = 566–2,759) in 2009 to 5,551 individuals (95% CI = 2,804–11,304) in 2006. Much of the annual variation in total abundance was attributable to wide variations in juvenile abundance, which ranged from a low of 62 individuals (95% CI = 24–181) in 2009 to a high of 3,467 individuals (95% CI = 1,744–7,095) in 2006. Annual shifts in size structure were indicative of rapid population turnover, probably resulting from a combination of mortality and permanent emigration. Although the Altamaha River Shortnose Sturgeon population shares several characteristics with northern populations (e.g., variable juvenile abundance and stable adult abundance), our results suggest that southern populations are more susceptible to decline because of their accelerated life cycle and inherently lower abundances.

Southern populations of the federally endangered Shortnose Sturgeon Acipenser brevirostrumare 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.

The visual and microscopic tissue reactions to the absorbable monofilament Monocryl, absorbable monofilament triclosan-coated Monocryl-Plus, absorbable multifilament Vicryl, and nonabsorbable monofilament Prolene were evaluated for their use of surgical closure in Siberian Sturgeon Acipenser baerii. Postoperative assessments were conducted at 1, 2, 8, 12, and 26 and 55 weeks to visually evaluate the surgical incision for suture retention, incision healing, erythema, and swelling. Incisions were also assessed microscopically at 1, 2, and 8 weeks for necrosis, inflammation, hemorrhage, and fibroplasia. The results indicated that incisions closed with either Vicryl or Prolene suture materials were more likely to exhibit more erythema or incomplete healing compared with those closed with Monocryl or Monocryl-Plus. The surgical implantation of a transmitter in the coelomic cavity did not significantly affect the response variables among the four suture materials. Monocryl or Monocryl-Plus were equally effective and superior to other suture materials used for closing surgical incisions in Siberian Sturgeon or closely related species of sturgeon. Furthermore, Monocryl or Monocryl-Plus may decrease the risk of transmitter expulsion through the incision, as surgical wounds appear to heal faster and exhibit less erythema compared with those closed with Vicryl.

The objective of our study was to estimate total bycatch and mortality of shortnose sturgeon Acipenser brevirostrumin the anchored-gill-net portion of the commercial fishery for American shad Alosa sapidissimain the Altamaha River, Georgia, from 2007 to 2009. We conducted on-the-water counts of commercial nets to estimate total fishing effort. Catch per unit effort was estimated from log books and direct observations of net retrievals by randomly selected commercial fishermen. During the 3 years of the study, the total estimated bycatch of shortnose sturgeon was 71, 53, and 498 fish, respectively. Recent studies have estimated the abundance of adult shortnose sturgeon in the Altamaha River to be approximately 1,800 individuals. Our study showed that catch per unit effort was highest during January and February of 2009 in upriver areas where previous research had identified several spawning locations. Our results also showed that the mortality of captured shortnose sturgeon was low in all 3 years (<8%), although we did not assess postrelease survival. Although closure of critical habitats may or may not be an important component of protecting shortnose sturgeon spawning habitat, our results suggest that on the Altamaha River, delaying the opening of commercial American shad fishing in the upper river until after 1 March would almost completely eliminate bycatch of migrating shortnose sturgeon and result in a minor reduction in American shad landings. Received February 16, 2011; accepted February 16, 2012

The shortnose sturgeon Acipenser brevirostrumis 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.

Juvenile Atlantic sturgeon Acipenser oxyrinchusremain in natal rivers for several years prior to out-migrating to marine environments during later portions of their life history. Data regarding river-resident juvenile population dynamics are unknown. During the summers of 2004–2007, we performed mark–recapture of juvenile Atlantic sturgeon in the Altamaha River to assess age-specific abundance, apparent survival, per capita recruitment, and factors influencing recruitment. Estimates indicated that juvenile abundance ranged from 1,072 to 2,033 individuals, and age-1 and age-2 individuals comprised greater than 87% of the juvenile population, while age-3 or older individuals constituted less than 13% of the population. Estimates of apparent survival and per capita recruitment from Pradel models indicated that the juvenile population experienced high annual turnover: apparent survival rates were low (<33%), and per capita recruitment was high (0.82–1.38). Fall discharge, which had a positive relationship with recruitment, was the only factor assessed that significantly explained time variation in per capita recruitment. The findings of this study suggest that juvenile populations at the southern extreme of the Atlantic sturgeon's range may remain in natal rivers for less time than northern counterparts. This is further evidence of life history differences between northern and southern populations of Atlantic sturgeon. Potential findings of density dependence could have major implications for both population recovery and management of this species.

Anthropogenic modifications of rivers and estuarine habitats have reduced the growth and recruitment of shortnose sturgeon Acipenser brevirostrumthroughout its native range. This study used data from laboratory experiments to examine the individual and interactive effects of salinity, temperature, and fish weight on the survival of young-of-year shortnose sturgeon. The shortnose sturgeon in these experiments ranged from 56 to 187 mm in total length, from 0.4 to 42.8 g in weight, and from 66 to 144 d posthatch in age. Survival in 23°C water declined as salinity increased, but salinity tolerance increased with body size. The salinity lethal to 50% of the test fish after 48 h ranged from 14.8‰ to 20.9‰. Survival in freshwater declined as temperature increased, but temperature tolerance increased with body size. The temperature lethal to 50% of the test fish after 48 h ranged from 28.2°C to 30.7°C. In factorial experiments, salinity and temperature interacted significantly to affect young-of-year survival. The results of the factorial experiments were used to generate a predictive model in which the probability of survival was dependent on salinity, temperature, fish weight, and all interactions among the variables. The results of this study can be used to identify suitable habitats for young-of-year shortnose sturgeon. The results of this study also can be used to predict the recruitment bottlenecks that may result from additional anthropogenic disturbances to rivers in the southeastern United States.

Although the Altamaha River, Georgia, once supported one of the largest fisheries for Atlantic sturgeon Acipenser oxyrinchusin U.S. waters, the fishery was closed in 1997 because of severe overfishing. Since then, no studies have been conducted and population trends have remained unknown. The objective of this study was to estimate annual run size and age structure of the spring spawning migration and to determine genetic relatedness between this population and other Georgia populations. In spring of 2004 and 2005, we sampled the annual spawning run of Atlantic sturgeon in the lower 30 km of the Altamaha River using large-mesh gill nets. Captured fish were marked with passive integrated transponder tags and released to facilitate a run estimate using a simple Schnabel mark-recapture estimator. Over the 2 years of the study, we captured 213 individuals, yielding mark-recapture run estimates of 324 (95% confidence interval [CI] = 143-667) in 2004 and 386 (95% CI = 216-787) in 2005. Catch curve analysis yielded annual mortality rates of 17.3% in 2004 and 21.3% in 2005. Genetic analysis showed that the Altamaha River population is distinct from neighboring populations in the Ogeechee and Savannah rivers. The results of this study suggest that after 10 years of federal protection, the Altamaha River population of Atlantic sturgeon appears to be in the early stages of recovery; however, the genetic diversity of the population is surprisingly low. Future studies are needed to monitor population dynamics and genetic structure of the stock to ensure complete recovery.

The Hudson River supports one of the largest remaining populations of Atlantic sturgeon Acipenser oxyrinchus; however, recent evidence of major declines in recruitment during the past decade suggests that the population may be in jeopardy. The scarcity of juveniles observed in recent years suggests that current levels of recruitment are too low to sustain the population. The primary goal of this study was to attain quantitative data on recruitment rates of juvenile Atlantic sturgeon in the Hudson River. From Jun through Oct 1995, hatchery-reared juveniles, marked and released in 1994, were collected with wild juveniles by randomized gill-net sampling distributed throughout the known distribution of age-1 juveniles. All stocked fish were double-marked with a clipped pelvic fin and an internal coded wire tag. During the sampling period we captured 15 marked and 14 unmarked age-1 Atlantic sturgeon. Using a Petersen mark–recapture population estimator, we calculated that there were 4,314 wild age-1 Atlantic sturgeon in the Hudson River in 1995, a decline of about 80% from the similarly conducted population estimate of 1977. This estimate, along with other current fisheries monitoring data, provides evidence of a substantial decline in recruitment during the past decade.

Sturgeons (family Acipenseridae) are a highly threatened taxon worldwide; populations have declined for several reasons, including overfishing and habitat modification. It has been suggested that the widely introduced, highly piscivorous, flathead catfish Pylodictis olivarisis responsible for the decline of certain sturgeon populations in North America. Here we present the first field observation of flathead catfish predation on a sturgeon of any species, an Atlantic sturgeon Acipenser oxyrinchusin the Satilla River, Georgia. Our finding demonstrates a potential impact of flathead catfish predation on sturgeon populations; however, more research is needed to describe the full magnitude of such effects on sturgeon populations.