Douglas L. Peterson

Ecology and biology of the lake sturgeon: a synthesis of current knowledge of a threatened North American Acipenseridae

The lake sturgeon is one of the largest North American freshwater fish and was once common in most inland rivers and lakes of the US and Canadian Midwest. World demand for caviar and sturgeon meat led to a dramatic decline of lake sturgeon populations throughout much of its range. Along with overfishing, lake sturgeon populations have been negatively affected by habitat degradation. Recruitment factors and early life history are poorly understood. Today, renewed interest in lake sturgeon restoration has led to numerous state and federally-funded research activities. Research has focused on identifying and assessing the size structure of remnant stocks, the availability of spawning habitat, and factors affecting reproductive success. Additional studies are needed to improve hatchery techniques, to better understand recruitment mechanisms, and how genetic diversity among and within meta-populations may affect long-term recovery of depleted populations.

Annual Run Size and Genetic Characteristics of Atlantic Sturgeon in the Altamaha River, Georgia

Abstract Although the Altamaha River, Georgia, once supported one of the largest fisheries for Atlantic sturgeon Acipenser oxyrinchus in 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 ana...

RANGE-WIDE POPULATION STRUCTURE OF SHORTNOSE STURGEON ACIPENSER BREVIROSTRUM BASED ON SEQUENCE ANALYSIS OF THE MITOCHONDRIAL DNA CONTROL REGION

Riverine populations of shortnose sturgeon (Acipenser brevirostrum) once occurred in rivers and estuaries along the east coast of North America from the St. John River, New Brunswick, to the St. Johns River, Florida. Within this range, 19 population segments were identified by the U.S. Federal Shortnose Sturgeon Recovery Team; empirical data supporting this structure is limited. We obtained samples from 11 (12 including a small sample from the Cape Fear River, North Carolina) of these population segments and used PCR and direct sequence analysis of 440 base pairs of the mitochondrial DNA (mtDNA) control region to define the coast-wide genetic population structure of shortnose sturgeon. Collections from most population segments exhibited significant differences in haplotype frequencies with their nearest neighbors, including from the Ogeechee and Savannah Rivers, Georgia (despite the known movement of hatchery-reared offspring from the Savannah into the Ogeechee River). Collections from the Chesapeake Bay and Delaware River exhibited similar haplotype frequencies, suggesting that specimens collected in the Chesapeake Bay had dispersed from the Delaware River. Collections from the Kennebec River and Androscoggin River within a hypothesized single population segment did not exhibit significant differentiation of mtDNA haplotype frequencies. Haplotype frequencies were almost identical between collections from above and below the Holyoke Dam on the Connecticut River, indicating that these aggregations should be managed as a single unit. Our results support the population segment status afforded to shortnose sturgeon in at least the following 9 systems; St. John River, Kennebec-Androscoggin Rivers, upper-lower Connecticut River, Hudson River, Delaware River-Chesapeake Bay, Pee Dee River, Cooper River, Savannah River, and Ogeechee-Altamaha Rivers.

Effects of Salinity, Temperature, and Weight on the Survival of Young-of-Year Shortnose Sturgeon

Abstract Anthropogenic modifications of rivers and estuarine habitats have reduced the growth and recruitment of shortnose sturgeon Acipenser brevirostrum throughout 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 su...

Abundance and Recruitment of Juvenile Atlantic Sturgeon in the Altamaha River, Georgia

Abstract Juvenile Atlantic sturgeon Acipenser oxyrinchus remain 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 relati...

Threatened fishes of the world: Huso huso (Linnaeus, 1758) (Acipenseridae)

D 48-81, A 22-41rays, dorsal scutes 9-17, lateral scutes 28-60 and ventral scutes 7-14.Body is heavy set, spindle-shaped with greatest body depth slightlyanterior to midsection. Large individuals often appear humpbacked.Conical rostrum contains numerous sensory pits on both ventral anddorsal surfaces. Sensory pits not restricted to rostrum and are presentin lesser numbers on the cheeks and posteriorly to the eye. Two pairsof barbells, long and laterally compressed with foliate appendages,originating midway or closer to the mouth than tip of snout. Enormous, crescent shaped mouth ventrally situated butunlike other acipenserids, projects forward. Upper lip continuous while lower lip is interrupted by large gap. Skin surfacecovered by fine denticles and five horizontal rows of scutes. On adults, scutes undergo absorption. Pre-anal plates 0–3 insingle file. Beluga may reach a maximum size of 1220kg and 6m in length (Balon 1967). Fully grown individuals havebecome exceedingly rare but a 960kg, 3.4m specimen was recently taken off the Mazandaran coast of the south CaspianSea. Adult coloration is gray, blue gray or dark brown with silver or gray lateral surface. Dark dorsum contrasts stronglyagainst rest of body. Large juveniles often exhibit a metallic sheen laterally which fades with age. Ventral surface iswhite or cream colored. Illustrations: (a) juvenile, hatchery origin 110cm, (b) adult, Volga River 180-cm male, (c) Volga

Critical linkage of imperiled species: Gulf Sturgeon as host for Purple Bankclimber mussels

Abstract.  One of the largest impediments to the conservation of freshwater mussels is the absence of host-fish data. Suitable hosts must be present in sufficient numbers and occur at the appropriate time for successful mussel recruitment. Habitat degradation and fragmentation caused by dams and other anthropogenic alterations may reduce host availability. Host data are lacking for the federally threatened Purple Bankclimber mussel (Elliptoideus sloatianus), which is endemic to the Apalachicola–Chattahoochee–Flint basin (ACF) in Alabama, Florida, and Georgia, and the Ochlockonee basin in Florida and Georgia. We tested 29 fish species in 7 families as potential hosts for Purple Bankclimbers and observed high metamorphosis success (79–89%) with 4 species of sturgeon: Gulf (Acipenser oxyrinchus desotoi), Atlantic (Acipenser oxyrinchus oxyrinchus), Lake (Acipenser fulvescens), and Shortnose (Acipenser brevirostrum). Metamorphosis was less successful with Blackbanded Darters (Percina nigrofasciata) and Halloween Darters (Percina crypta) as hosts (34–36% metamorphosis), and the remainder of the fishes we tested were not suitable hosts. The federally threatened Gulf Sturgeon is the only sturgeon species present in the ACF, but access of this migratory fish to most of the basin is blocked by Jim Woodruff Dam on the Apalachicola River. In the absence of sturgeon upstream of Jim Woodruff Dam, darters appear to have facilitated persistence of this mussel species, but at abundances far lower than historical conditions. This relationship between the Purple Bankclimber and Gulf Sturgeon is the first description of a federally protected fish serving as a host for a federally protected mussel and is an archetypal example of the role of habitat fragmentation in the ecology of listed species. Recovery of the Purple Bankclimber and other mussel species probably will require restoration of habitat connectivity for fish passage.

Evidence of Metapopulation Dynamics in Shortnose Sturgeon in the Southern Part of Their Range

Abstract 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, ...

Past and Present Processes Influencing Genetic Diversity and Effective Population Size in a Natural Population of Atlantic Sturgeon

Abstract Threats such as habitat loss, invasive species, and overexploitation cause species extinctions; however, stochastic processes can accelerate extinction rates as census sizes decline. Using molecular and ecological data, we explored the influence of these processes on the demography of a candidate species under the U.S. Endangered Species Act—the Atlantic sturgeon Acipenser oxyrinchus oxyrinchus. We used molecular microsatellite markers to estimate the effective population size (Ne ) and effective number of breeders (Nb ) and we used mark–recapture data to estimate the number of spawners (Na ) for Atlantic sturgeon of the Altamaha River, Georgia. We found that estimates of Nb were 7–45% less than the estimated Na over four consecutive cohorts and that skewed sex ratios could explain the relative decrease of Nb to Na . Our estimate of contemporary Ne was 125 (95% confidence interval = 75–348) and was at least an order of magnitude less than our estimate of historical Ne . To explain the large discr...

Morphology and ecology of Pacific sturgeons

The six North Pacific members of the genus Acipenser have generally similar environmental requirements and share several specific morphological features. This Pacific group consists of green sturgeon, Acipenser medirostris, Sakhalin sturgeon, A. mikadoi, white sturgeon, A. transmontanus, Chinese sturgeon, A. sinensis, Dabry’s sturgeon, A. dabryanus and Amur sturgeon, A. schrenkii. A qualitative morphological examination of these species revealed synapomorphic characters that suggest close phyolgenetic relationships resulting from common ancestry of eastern and western species within the Pacific Rim. An evolutionary taxonomic approach, considering a reduction of characters from east to west, would suggest an Asian ancestry for all Pacific sturgeons. In contrast however, a phylogenetic approach using derived character states suggests a North American ancestry. Besides a common ancestry for Chinese and American sturgeons, the taxonomic status of A. mikadoi is discussed.