Atlantic Sturgeon Research Articles

A Novel Approach to Surveying Sturgeon Using Side‐Scan Sonar and Occupancy Modeling

AbstractTechnological advances represent opportunities to enhance and supplement traditional fisheries sampling approaches. One example with growing importance for fisheries research is hydroacoustic technologies such as side‐scan sonar. Advantages of side‐scan sonar over traditional techniques include the ability to sample large areas efficiently and the potential to survey fish without physical handling—important for species of conservation concern, such as endangered sturgeons. Our objectives were to design an efficient survey methodology for sampling Atlantic Sturgeon Acipenser oxyrinchus by using side‐scan sonar and to develop methods for analyzing these data. In North Carolina and South Carolina, we surveyed six rivers thought to contain varying abundances of sturgeon by using a combination of side‐scan sonar, telemetry, and video cameras (i.e., to sample jumping sturgeon). Lower reaches of each river near the saltwater–freshwater interface were surveyed on three occasions (generally successive days), and we used occupancy modeling to analyze these data. We were able to detect sturgeon in five of six rivers by using these methods. Side‐scan sonar was effective in detecting sturgeon, with estimated gear‐specific detection probabilities ranging from 0.2 to 0.5 and river‐specific occupancy estimates (per 2‐km river segment) ranging from 0.0 to 0.8. Future extensions of this occupancy modeling framework will involve the use of side‐scan sonar data to assess sturgeon habitat and abundance in different river systems.Received January 15, 2013; accepted June 10, 2013

Stock Origins of Subadult and Adult Atlantic Sturgeon, Acipenser oxyrinchus, in a Non-natal Estuary, Long Island Sound

The anadromous acipenserid Atlantic sturgeon Acipenser oxyrinchus was listed in 2012 under the U.S. Endangered Species Act as having four endangered and one threatened distinct population segment (DPS) in American waters. Anthropogenic activities outside of natal estuaries, particularly bycatch, may hinder the abilities of some populations to rebuild. Most Atlantic sturgeon are residential for their first 2–6 years within their natal estuaries, whereas older subadults and adults may migrate to non-natal estuaries and coastal locations. Previous studies demonstrated that subadults and adults aggregate during summer at locations in Long Island Sound (LIS) and its tributary, the Connecticut River; however, the population origin of these fish is unknown. Because of its geographic proximity and relatively robust population, we hypothesized that the LIS and Connecticut River aggregations were almost solely derived from the Hudson River. We used microsatellite nuclear DNA analysis at 11 loci and mitochondrial DNA control region sequence analyses to estimate the relative contributions of nine Atlantic sturgeon populations and the five DPS to these aggregations using individual-based assignment tests and mixed-stock analysis. From 64 to 73 % of specimens from LIS were estimated to be of Hudson origin. Similarly, 66–76 % of specimens from the Connecticut River were of Hudson origin. However, moderate numbers of specimens were detected from distant spawning populations in the southeastern DPS and from two populations once thought to be extirpated or nearly so, the James River (6–7.3 %), and the Delaware River (7.6–12 %). Additionally, specimens were detected from all five DPS in both the LIS and Connecticut River collections. These results highlight the difficulty of evaluating the status of individual Atlantic sturgeon populations because of the propensity of subadults and adults to migrate for extended duration to distant sites where they may be vulnerable to anthropogenic disturbances.

Palaeogenetics of western French sturgeons spotlights the relationships between Acipenser sturio and Acipenser oxyrinchus

AbstractAimThe Atlantic sturgeon, Acipenser oxyrinchus, was long considered an American species, but recent discoveries based on analyses of archaeological remains proved its presence in the Baltic Sea and in France. This came as a surprise, as the European sturgeon, Acipenser sturio, was thought to be the only sturgeon species present on the European Atlantic coast. It was hypothesized that migrants from North America founded the Baltic population of Atlantic sturgeons around 1200 years ago.LocationThe sampling is composed of five sturgeon archaeological remains (5000–1800 yr bp) and 21 naturalized or ethanol‐preserved museum specimens from the 19th and 20th centuries, originating from the French Atlantic coast.MethodsAnalyses of ancient DNA were performed following the strict criteria of the field to avoid contamination and to ensure sequence authentication. A 210‐bp fragment of the control region (CR) was sequenced and three microsatellite loci were sized and sequenced.ResultsOut of a total of 26 samples, three archaeological remains and six museum specimens produced A. oxyrinchus mitochondrial or nuclear sequences; two of these museum samples showed signs of hybridization between A. sturio and A. oxyrinchus. All the other samples yielded only A. sturio DNA sequences, and a new CR haplotype was described in this species.Main conclusionsMolecular evidence of sympatry and natural hybridization between A. sturio and A. oxyrinchus on the French Atlantic coast – specifically the hybrid evidence of two museum specimens collected from the Seine River in 1823 and 1858 – challenge our understanding of the species' past relationships. In light of these findings, new hypotheses are presented to explain the history and geographical range of A. oxyrinchus in Europe.

The Potential for Vessel Interactions with Adult Atlantic Sturgeon in the James River, Virginia

AbstractIn 2012, all populations of Atlantic sturgeon Acipenser oxyrinchus oxyrinchus were listed as either threatened or endangered under the U.S. Endangered Species Act. During 2007–2010, researchers documented 31 carcasses of adult Atlantic sturgeon in the tidal freshwater portion of the James River, Virginia. Twenty‐six of the carcasses had gashes from vessel propellers, and the remaining five carcasses were too decomposed to allow determination of the cause of death. The types of vessels responsible for these mortalities were not explicitly demonstrated. Most (84%) of the carcasses were found in a relatively narrow reach that was modified to increase shipping efficiency. To explore the number of Atlantic sturgeon being hit and their horizontal and depth distributions in relation to vessel draft, we conducted telemetry experiments on three living fish (all males) and six dead specimens. While staging (holding in an area from hours to days, with minimal upstream or downstream movements), the adult male Atlantic sturgeon spent most (62%) of the time within 1 m of the river bottom. Assuming that behavior is not modified by vessel noise, adult male Atlantic sturgeon in the James River would rarely encounter small recreational boats or tugboats with shallow drafts; instead, mortalities are likely caused by deep‐draft ocean cargo ships, which have drafts that coincide with the distribution of the tracked adult males. Dead specimens (n = 6) drifted with the current for several hours to almost 4 d before beaching at distances ranging from 0.5 to over 50 river kilometers from the point of release. We estimated that current monitoring in the James River documents less than one‐third of vessel strike mortalities. A better understanding of Atlantic sturgeon behavior in the presence of vessels will aid in restoring this federally endangered species.Received February 20, 2012; accepted July 19, 2012

Empirical Evidence of Fall Spawning by Atlantic Sturgeon in the James River, Virginia

AbstractDue to overfishing and habitat alteration, the anadromous Atlantic sturgeon Acipenser oxyrinchus oxyrinchus is severely depleted across its historic range. The James and York rivers in Virginia are the two rivers comprising the Chesapeake Bay distinct population segment, where Atlantic sturgeon reproduction has been confirmed. It is widely recognized that Atlantic sturgeon spawn in the spring throughout their range; however, there is debate over whether they also spawn in the fall. To determine if Atlantic sturgeon spawn in the fall, independent of the spring spawn, large‐mesh gill netting in the freshwater portion of the James River (above river kilometer 108) was conducted in the spring (April–June) and fall (August–October) for 3 years (2009–2011), resulting in the capture of 125 adult Atlantic sturgeon (three were recaptures) during the fall sampling, but none were captured during the spring. Field examination for sex and stage of maturity identified 106 mature males and one postspawned female. Sex was not determined for four fish, and due to time constraints, 11 were not examined. Forty mature males were externally tagged with Vemco© ultrasonic passives tags and movements were monitored with a Vemco© VR2W passive receiver array. Collection and tracking data showed that mature Atlantic sturgeon aggregate in the freshwater portion of the James River during the fall season, entering during August and out‐migrating by the end of November. No tagged fish were detected in the freshwater area of the river during the subsequent spring months. Though James River Atlantic sturgeon may spawn in the spring, we suggest there is strong evidence for an independent fall spawn, which should be considered in future management and recovery actions.

Effect of chloride on nitrite‐induced methaemoglobinemia in Atlantic sturgeon,Acipenser oxyrinchus oxyrinchus(Mitchill)

We evaluated the effects of chloride concentration on the clinical pathology in juvenile Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus (Mitchill), following semi-static exposures to 1 mg L(-1) nitrite for 96 h. In spring water naturally low in chloride (5 mg L(-1)), plasma nitrite concentrated to more than 40× environmental levels resulting in a severe methaemoglobinemia characterized by torpid behaviour, 30-fold increase in methaemoglobin fraction, anaemia, leucopenia and hyperkalaemia. Loss of intracellular water and potassium to extracellular space may have resulted in hyperkalaemia and haemodilution. Fish survived nitrite exposure, but 60% of torpid fish died following capture and tissue sampling. Fish acclimated to 10-fold higher chloride content (55 mg L(-1)) did not concentrate nitrite in the plasma above environmental levels or develop methaemoglobinemia, but did exhibit similar haematology and plasma chemistry changes. Plasma nitrite returned to preexposure levels by 14 days following nitrite exposures, but severity of clinical pathology changes persisted or increased, suggesting that Atlantic sturgeon have reduced capacity to recover from methaemoglobinemia. Fish that survive methaemoglobinemia may be susceptible to mortality from the cumulative effects of intoxication, handling and other stresses for two or more weeks following nitrite remediation. Chloride buffering in aquaculture systems reduces the toxic effects of nitrite accumulation.

Stock Origin of Migratory Atlantic Sturgeon in Minas Basin, Inner Bay of Fundy, Canada, Determined by Microsatellite and Mitochondrial DNA Analyses

AbstractFive distinct population segments of Atlantic sturgeon Acipenser oxyrinchus were recently listed (April 2012) as endangered or threatened under the U.S. Endangered Species Act. Atlantic sturgeon are anadromous, spawning occurs in rivers from the St. Lawrence River, Quebec, to the Satilla River, Georgia, and subadults and adults undertake extensive coastal migrations. Bycatch of Atlantic sturgeon in coastal fisheries may have resulted in the slowed or failed rebuilding of many populations despite the imposition of a U.S. federal moratorium on their harvest in 1998. Canada's Bay of Fundy hosts weir and trawl fisheries which bycatch Atlantic sturgeon of unknown origin. Additionally, tidal power development projects for the Bay of Fundy have been proposed which could detrimentally impact migratory sturgeon. We hypothesized that the Atlantic sturgeon that occur in Minas Basin in the Bay of Fundy are of local Saint John River, New Brunswick, origin with little or no U.S. contribution. We used microsatellite DNA (11 loci) and mitochondrial DNA control region sequence analysis along with previously determined characterizations of nine reference spawning populations to quantify their stock origin. We determined that the summer assemblage of Atlantic sturgeon collected within Minas Basin was of mixed origin, with a greater than 60% contribution from the nearby Saint John River but with a substantial (34–36%) contribution from the Kennebec River, Maine, and a smaller (1–2%) contribution from the Hudson River, New York. There was significant genetic heterogeneity between smaller (<130 cm) and larger individuals (≥130 cm) in Minas Basin; however, the smaller specimens were not exclusively of proximal Saint John River origin. Our results indicate that Atlantic sturgeon of U.S. origin are vulnerable to anthropogenic impacts in the Bay of Fundy, particularly those of Kennebec River origin.

Toxic effects of PCB126 and TCDD on shortnose sturgeon and Atlantic sturgeon

Exposure to chemical contaminants is often invoked to explain recruitment failures to populations of sturgeon worldwide, but there is little empirical evidence to support the idea that young sturgeon are sensitive at environmentally relevant concentrations. The authors used shortnose sturgeon (Acipenser brevirostum) and Atlantic sturgeon (Acipenser oxyrinchus) as models to investigate the sensitivities of sturgeon to early-life-stage toxicities from embryonic exposures to graded doses of polychlorinated biphenyl 126 (PCB126) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Survival to hatching of shortnose sturgeon decreased with increasing dose, although the duration of the embryonic period was not significantly altered by exposure in either species. Morphometric features of larvae of both species were affected by dose, including shortening of the body, reduction in head size, reduction in quantity of yolk reserves, and reduction in eye size. Eye development in both species was delayed with increasing dose for both chemicals. The persistence of larvae in a food-free environment decreased inversely with dose in both species, with sharp declines occurring at PCB126 and TCDD doses of ≥1 ppb and ≥0.1 ppb, respectively. Dose-responsive early-life-stage toxicities reported here are among the more sensitive found in fish and occurred at burdens similar to those found in situ in a sympatric bottom-dwelling bony fish in the Hudson River Estuary. The present study is among the first demonstrating the sensitivity of any sturgeon to the hallmark early-life-stage toxicities induced by aryl hydrocarbon receptor agonists.

Immunophysiology of Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus (Mitchill), and the relationship to parasitic copepod, Dichelesthium oblongum (Abilgaard) infection

The copepod parasite, Dichelesthium oblongum, is known to infect the Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus, within the area near New York city, USA, known as the NY Bight. The gross pathology associated with the juvenile and adult copepod stages along with the parasite's link in causing changes in sturgeon osmoregulatory capabilities has led us to investigate the host immunophysiology in relation to this host-parasite system. All the host variables, which included gill Na(+) -K(+) -ATPase activity, serum alkaline phosphatase (AP) and white blood cell differential counts, were affected in a non-linear manner by the copepod parasite. The parasites increased the host gill Na(+) -K(+) -ATPase activity and serum AP along with the percentage granulocytes while decreasing the percentage lymphocytes. A new method, developed to sample and preserve white blood cells in the field for future flow cytometry analysis, proved adequate. The effects of fish size, location and time of sampling were accounted for by the use of generalized linear models, and their effects on the host variables are discussed.

Age and Growth of Atlantic Sturgeon in the James River, Virginia, 1997–2011

AbstractHistorically the Chesapeake Bay supported a large population of Atlantic sturgeonAcipenser oxyrinchus, but loss of suitable spawning habitat and overfishing coincided with dramatic in‐system declines throughout the 20th century. Atlantic sturgeon harvest moratoriums were implemented in 1974 for Virginia waters and were expanded coastwide in 1998. In 1997, researchers became aware that commercial fishers in the James River, a tributary of the Chesapeake Bay, were catching juvenile and subadult Atlantic sturgeon as bycatch in various fisheries. Genetic studies showed that the Chesapeake Bay population has maintained genetic integrity and qualifies as a distinct population segment. Between 2007 and 2011, almost 150 adults have been caught in the tidal–freshwater portion of the James River during putative spawning runs. Pectoral fin spines from juveniles and subadults collected in the Burwell Bay (rkm 40) and Cobham Bay (rkm 60) areas and mature adult samples from vessel strikes in freshwater around or above rkm 120 were analyzed to create a length‐at‐age curve for Atlantic sturgeon in the James River. Five models were used to analyze the data, and the double von Bertalanffy (k1= 0.054,k2= 0.097,t1= −2.85,t2= 1.09,tp= 6.03 years,L∞= 2241 mm) provided the best fit to the observed data. We estimated an increase in growth coefficient attp, which could be an artifact of low sample size or due to ontogenetic changes in habitat use as older fish spend more time in oceanic waters than younger fish. Atlantic sturgeon in the 6–9 year age range are rarely encountered in the James River compared with younger and older age‐classes, so a more in‐depth analysis of the increased growth coefficient would require ocean sampling.

Growth and Survival of Hatchery-Produced Atlantic Sturgeon Released as Young-of-Year into the Hudson River, New York

Abstract In 2007, a team of U.S. scientists performed a status review of Atlantic sturgeon Acipenser oxyrinchus oxyrinchus and concluded that the species would likely become endangered (U.S. Endangered Species Act 1973, as amended) in the foreseeable future over much of its range, including populations of the New York Bight, which is comprised of the Hudson and Delaware rivers. Therefore, we evaluated an experimental release of hatchery-produced Atlantic sturgeon that took place in 1994 to determine the value of using stocked fish as a population recovery tool. We obtained recapture data on hatchery fish (identified by presence of pelvic fin removal) from the Atlantic Coast Sturgeon Tagging Database. Our evaluation of retention for a pelvic fin removal mark on hatchery fish showed that 36% of clipped individuals retained a clean fin clip after 49 d. The minimum survival rate for hatchery fish to age 5 was estimated to be in the range of 0.49–0.66% using documented recaptures (N = 24), known number of fish stocked, and results of the pelvic fin removal evaluation. Length and weight-at-age for recaptured hatchery fish at known ages 5–17 were within the range of values reported for wild fish whose ages were estimated by pectoral spine analysis. We also report that one ripe male hatchery fish at age 15 was captured along with other spermiating males at its parental spawning area in the Hudson River in 2009.

Using energy dispersive x-ray fluorescence microchemistry to infer migratory life history of Atlantic sturgeon

Atlantic sturgeon migrate between ocean and freshwater habitats to spawn, and juveniles spend several years in fresh/brackish water before returning to the ocean. Because strontium/calcium (Sr/Ca) ratios are diagnostic for freshwater and marine environments, we examined the utility of energy-dispersive x-ray fluorescence (EDXRF) to quantify Sr/Ca ratios of Atlantic sturgeon pectoral fin spines. Atlantic sturgeon spines from wild adults and experimental juveniles were analyzed along a linear transect from the primordium to the outermost point. To verify the technique hatchery juvenile Atlantic sturgeon were held in experimental tanks at <0.5, 13–15, or 33–35‰ and sampled after 5 months. Sr/Ca ratios of experimental hatchery fish increased with salinity, and Sr/Ca ratios in wild adults varied predictably along the measurement transect. However, the ratio decreased in the outermost region of the spine in mature fish collected during a return to freshwater for spawning. Therefore EDXRF is a useful tool to track individual movements of Atlantic sturgeons and other diadromous fish.

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

AbstractThreats 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 discrepancy between these estimates, we tested several alternative evolutionary scenarios that might explain the observed pattern of genetic diversity. Our results indicated that the observed genetic data were indeed best explained (i.e., 0.998 posterior probability of the data given the hypothesis) by overexploitation during the last half of the 20th century.

Evaluating Changes in Diadromous Species Distributions and Habitat Accessibility following the Penobscot River Restoration Project

AbstractThe Penobscot River basin, covering approximately 22,265 km2, is the largest river wholly within Maine and the second largest river system in New England. The Penobscot River Restoration Project (PRRP) is a multimillion‐dollar endeavor that aims to restore native sea‐run fish through the removal of two main‐stem dams and improved fish passage at a third dam on the Penobscot River. We used geographical information systems, accounts of historic ranges, and barrier survey data to estimate species‐specific distributions and habitat accessibility for 11 diadromous species before and after the proposed restoration. We predict a range of outcomes in terms of expected distribution and accessibility that are largely based on habitat use and life history differences. For 4 out of 11 species (Atlantic sturgeon Acipenser oxyrinchus, shortnose sturgeon A. brevirostrum, Atlantic tomcod Microgadus tomcod, and striped bass Morone saxatillis), the PRRP is anticipated to provide access to 100% of their historic freshwater habitat. However, for alewives Alosa pseudoharengus, approximately 69% of the historic spawning and rearing habitat will remain inaccessible due to the presence of other passage barriers. Our results demonstrate that the PRRP is an important step toward ecosystem recovery in the Penobscot River basin but that other restoration activities will be needed to realize the full potential of the PRRP, particularly for alosines. Further, our results provide the first spatial analysis of diadromous fish distribution and access following the PRRP and serve as the baseline for developing a guiding image for expected diadromous fish population responses following the dam removals.Received March 21, 2011; accepted August 21, 2011

Isolation of cells from Atlantic sturgeon Acipenser oxyrinchus oxyrinchus and optimization of culture conditions

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 14:67-75 (2011) - DOI: https://doi.org/10.3354/ab00383 Isolation of cells from Atlantic sturgeon Acipenser oxyrinchus oxyrinchus and optimization of culture conditions B. Grunow*, S. Noglick, C. Kruse, M. Gebert Fraunhofer Research Institution for Marine Biotechnology, Fraunhofer Society, Paul-Ehrlich-Straße 1–3, 23562 Lübeck, Germany *Email: bianka.grunow@emb.fraunhofer.de ABSTRACT: We describe a method for fast and easy isolation of cells via trypsin digestion from larvae of Atlantic sturgeon Acipenser oxyrinchus oxyrinchus resulting in a stable, well-proliferating cell culture. The culture conditions for these cells were optimized with the aim of supporting the production of high amounts of biomass. To enhance cell growth and cell density, 4 different cultivation temperatures as well as commercially available carp serum (CS) and fetal calf serum (FCS) at different concentrations were tested and evaluated. Cell growth was measured via an impedance-based online cell-monitoring system (xCELLigence). These results showed the best cultivation temperature to be at 25°C and a media composition of Dulbecco’s modified Eagle’s medium (DMEM) supplemented with either 10 or 20% FCS or 5% CS. The cells were stable in the process of long-term cultivation over 33 passages and could be cryo-preserved. Immunocytochemical analysis revealed that the cells expressed proteins of different blastodermic layers. Ectodermic glia fibrilliary acid protein, vigilin (mRNA transport protein), and pan cytokeratin were abundant. This fast-growing cell culture provides an important tool for research on Atlantic sturgeon populations. KEY WORDS: Primary culture · Culture condition · Serum · Sturgeon · Teleost fish Full text in pdf format PreviousNextCite this article as: Grunow B, Noglick S, Kruse C, Gebert M (2011) Isolation of cells from Atlantic sturgeon Acipenser oxyrinchus oxyrinchus and optimization of culture conditions. Aquat Biol 14:67-75. https://doi.org/10.3354/ab00383 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 14, No. 1. Online publication date: December 06, 2011 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2011 Inter-Research.

Genetic mixed‐stock analysis of Atlantic sturgeon Acipenser oxyrinchus oxyrinchus in a heavily exploited marine habitat indicates the need for routine genetic monitoring

Although a previous genetic mixed-stock analysis (gMSA) conducted in the early 1990s showed that marine-captured New York Bight Atlantic sturgeon Acipenser oxyrinchus oxyrinchus almost exclusively originated from the Hudson River, fish from southern U.S. rivers were well represented within this contemporary sample (n = 364 fish), at least during the autumn. Widely distributed spawning stocks are therefore exposed to heavy fishing activity and habitat degradation in this relatively small area, illustrating the need for spatial management across multiple management jurisdictions and routine gMSA to account for temporal change.

Quality Assessment of Wild Atlantic Sturgeon Semen under Conditions of Short‐Term Storage

AbstractShort‐term storage trials were conducted with semen of Atlantic sturgeon Acipenser oxyrinchus collected from a total of nine wild males during the 2008 and 2009 spawning seasons on the Hudson River. Semen samples were kept refrigerated (4 ± 1°C) and stored in different gaseous atmospheres and storage extenders. The gaseous environments included oxygen, nitrogen, and air, while the extender treatments included modified Tsvetkova (MT), Park and Chapman (PC), and undiluted. Analyses of four response variables—percent viable sperm (viability), percent motile sperm (motility), curvilinear velocity (VCL), and ATP content—were determined on the day of arrival in the laboratory and then every other day for 7 d in 2008 and 21 d in 2009. The experiments were conducted in a split‐split‐plot design to examine dilution treatment, gas atmosphere, and repeated measures across days, and linear analyses of covariance models were fit to the data after appropriate transformation. Storage of sperm in an oxygen atmosphere was superior to storage in a nitrogen atmosphere for all variables. Storage of semen in 100% or 21% (air) oxygen in PC did not lead to differences among variables except for viability; viability was maintained at more than 95% through 13 d, decreasing to 88% and 94% on day 21 in 100% oxygen and air, respectively. During the last 5 d survival in an air atmosphere was better than that in 100% oxygen. Motility decreased during the 21 d of storage and the decline was greater in undiluted than in PC‐extended semen, decreasing from 85% on day 1 to approximately 21% and 47%, respectively, on day 21. We conclude that for Atlantic sturgeon semen storage, PC is the extender of choice and semen viability can be maintained for up to 21 d with some expectation of successful fertilization.

The effects of temperature on the physiological response to low oxygen in Atlantic sturgeon

Atlantic sturgeon (Acipenser oxyrhynchus), which are bottom dwelling and migratory fish, experience environmental hypoxia in their natural environment. Atlantic sturgeon, acclimated to either 5 or 15°C, were subjected to a 1 h severe (<10 mm Hg) hypoxia challenge in order to document their physiological responses. We measured hematological parameters, including O(2) transport (hemoglobin, hematocrit), ionic (chloride, osmolality), and metabolic (glucose, lactate) variables under normoxic conditions (~160 mm Hg), immediately following a 1 h exposure to hypoxic water, and following a further 2 h of recovery from this challenge in normoxic water. In a second experiment, we assessed the opercular beat frequency before, during, and after hypoxic exposure. Hemoglobin concentrations and hematocrit were significantly different between fish held at 5°C vs. 15°C and also significantly different between normoxia prior to hypoxia and following recovery. Plasma lactate concentrations increased following hypoxia at both temperatures, indicative of an increase in anaerobic metabolism. In contrast, a significant increase in plasma glucose concentrations in response to hypoxia only occurred at 5°C, suggesting different fuel demands under different temperatures. Changes in opercular beat frequency (OBF) were dependent on temperature. At 5°C, OBF increased upon exposure to hypoxia, but returned to pre-exposure levels within 35 min for the remainder of the experiment. During hypoxia at 15°C, OBF increased very briefly, but then rapidly (within 20 min) decreased to levels below control values. Following a return to normoxia, OBF quickly increased to control levels. Overall, these findings suggest that Atlantic sturgeons are relatively tolerant to short-term and severe hypoxic stress, and the strategies for hypoxia tolerance may be temperature dependent.

Characterization and expression of cytochrome P4501A in Atlantic sturgeon and shortnose sturgeon experimentally exposed to coplanar PCB 126 and TCDD

The AHR pathway activates transcription of CYP1A and mediates most toxic responses from exposure to halogenated aromatic hydrocarbon contaminants such as PCBs and PCDD/Fs. Therefore, expression of CYP1A is predictive of most higher level toxic responses from these chemicals. To date, no study had developed an assay to quantify CYP1A expression in any sturgeon species. We addressed this deficiency by partially characterizing CYP1A in Atlantic sturgeon ( Acipenser oxyrinchus oxyrinchus) and shortnose sturgeon ( Acipenser brevirostrum) and then used derived sturgeon sequences to develop reverse transcriptase (RT)-PCR assays to quantify CYP1A mRNA expression in TCDD and PCB126 treated early life-stages of both species. Phylogenetic analysis of CYP1A, CYP1B, CYP1C and CYP3A deduced amino acid sequences from other fishes and sturgeons revealed that our putative Atlantic sturgeon and shortnose sturgeon CYP1A sequences most closely clustered with previously derived CYP1A sequences. We then used semi-quantitative and real-time RT-PCR to measure CYP1A mRNA levels in newly hatched Atlantic sturgeon and shortnose sturgeon larvae that were exposed to graded doses of waterborne PCB126 (0.01–1000 parts per billion (ppb)) and TCDD (0.001–10 ppb). We initially observed significant induction of CYP1A mRNA compared to vehicle control at the lowest doses of PCB126 and TCDD used, 0.01 ppb and 0.001 ppb, respectively. Significant induction was observed at all doses of both chemicals although lower expression was seen at the highest doses. We also compared CYP1A expression among tissues of i.p. injected shortnose sturgeon and found significant inducibility in heart, intestine, and liver, but not in blood, gill, or pectoral fin clips. For the first time, our results indicate that young life-stages of sturgeons are sensitive to AHR ligands at environmentally relevant concentrations, however, it is yet to be determined if induction of CYP1A can be used as a biomarker in environmental biomonitoring.

Use of pop-up satellite archival tags to identify oceanic-migratory patterns for adult Atlantic Sturgeon, Acipenser oxyrinchus oxyrinchus Mitchell, 1815

Summary Oceanic-migratory behavior of adult Atlantic Sturgeon, Acipenser oxyrinchus oxyrinchus, was examined using pop-up satellite archival tags (PSAT). Twenty-three Atlantic Sturgeons were caught and tagged with PSATs in the Hudson River, New York during 2006 and 2007. Fifteen of those fish returned to the ocean (with PSATs attached) 6–132 days after tagging. These PSATs remained attached to fish for a period of 108–360 days archiving light, temperature, and depth, before releasing from fish, ascending to the surface, and transmitting data to satellites. The location of PSATs was measured to within ±150 m by satellites using Doppler shift of radio transmissions within hours after tags reached the surface. Positions prior to pop up were initially estimated using only archived-light data and the tag manufacturers’ proprietary software. Positional error associated with light-based estimates is high, especially with regard to latitude. This error was reduced by applying depth, distance, and temperature filters. Thirteen of the 15 Atlantic Sturgeons that left the Hudson River with PSATs attached remained within the Mid-Atlantic Bight for up to 1 year after tagging. Their geographic distributions generally extended from Long Island, New York to Chesapeake Bay at depths between 5 and 40 m. Aggregation areas were identified off southwest Long Island, along the New Jersey coast, off Delaware Bay, and off Chesapeake Bay. Depth distribution was seasonal; fish inhabited deepest waters during winter and shallowest waters during summer and early fall. Two Atlantic Sturgeons traveled outside of the Mid-Atlantic Bight. One migrated north to Cobequid Bay (terminal end of the Bay of Fundy, Nova Scotia), whereas the other traveled south to the coast of Georgia.