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Sturgeon populations worldwide are threatened with extirpation but little is known about their tendency to bioaccumulate contaminants and their sensitivities to environmental burdens of these contaminants. Shortnose sturgeon and Atlantic sturgeon, two species that are federally endangered in the U.S., co-occur in the Hudson River (HR) where high sediment levels of PCBs and PCDD/Fs occur. Previous controlled laboratory studies showed that young life-stages of both species are sensitive to toxicities at low levels of TCDD and PCB126 exposure. The objective here was to measure congener-specific hepatic levels of PCBs and PCDD/Fs in HR specimens in order to determine if in situ bioaccumulation of these compounds was sufficiently high to cause the early life-stage toxicities previously observed. Estimates of hepatic burdens of PCBs and PCDD/Fs were obtained from a small number of specimens of each species collected between 2014 and 2016 and specimens of shortnose sturgeon collected over 30 yr earlier and archived in a museum collection. Several significant patterns emerged. Hepatic levels of legacy PCBs and PCDDs were low in specimens of both species, but typically higher in shortnose than Atlantic sturgeon, a pattern consistent with their habitat use in the HR. Hepatic burdens from archived specimens of shortnose sturgeon tended to be higher than more recently collected ones despite expected reduction in their burdens due to preservation methods. Several inadvertent PCBs congeners were detected, including PCB11, but their possible toxicity to natural populations remains to be determined in future experiments. Levels of select PCDFs congeners, 2,3,7,8-TCDF and 2,3,4,7,8 PeCDF, were elevated in some shortnose sturgeon individuals from the HR. Using Relative Potency (ReP) factors derived from white sturgeon, the observed levels of some hepatic PCDFs in HR shortnose sturgeon may have been sufficiently high to impair recruitment of young life-stages in this ecosystem.

Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) is a long-lived, anadromous species that is broadly distributed along the Atlantic coast of North America. Historic overharvest and habitat degradation resulted in significant declines to Atlantic sturgeon populations and, following decades of limited recovery, the species was listed under the Endangered Species Act of the United States in 2012. Given continued threats to recovery and limited information about population demography, there is a need for new tools to assist in Atlantic sturgeon conservation. Here, we present a range-wide microsatellite genetic baseline for North American Atlantic sturgeon that is comprised of 2510 individuals from 18 genetically distinct groups collected in 13 rivers and one estuary. Analysis of this baseline suggested that populations from the northern range of Atlantic sturgeon were more highly differentiated than those from the southern extent, where patterns of differentiation were complicated by rivers with genetically distinct spring and fall spawning runs and less geographic distance separating populations. Despite significant demographic bottleneck events, all populations showed at least moderate levels of genetic diversity across a suite of metrics. Additionally, individual-based assignment tests had over 80% accuracy for assigning individuals to their river of origin, highlighting the utility of this baseline for characterizing the composition of mixed-stock aggregations and understanding stock-specific vulnerability and recovery. The expanded spatial coverage of this baseline dataset enabled novel inferences about patterns of genetic differentiation and spawning phenology in Atlantic sturgeon which can be used to support conservation and management efforts.

Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) is an anadromous, widely distributed, highly migratory sturgeon subspecies that occurs in rivers and marine waters along the North American Atlantic Coast. This fish has shown widespread declines and has been afforded conservation protections, including some based in the U.S. on the delineation of Distinct Population Segments (DPS) under the Endangered Species Act. The management of Atlantic sturgeon will benefit from the knowledge of its population structure as well as the ability to uniquely identify individuals (in relation to population origin) that are vulnerable to anthropogenic stressors at sites outside of their natal estuaries. We used microsatellite analysis to estimate the genetic population structure of Atlantic sturgeon from 13 spawning rivers ranging from the St. Lawrence River, Quebec to the Satilla River, Georgia. Individual Based Assignment (IBA) testing was used to estimate the contribution of each population to mixed-stock aggregations in coastal waters and in a non-natal estuary. An unexpected finding was the discovery of two distinct genetic clusters of juvenile Atlantic sturgeon in the Ogeechee River, Georgia, with specimens in the two clusters differing significantly in terms of mean total length. Additionally, three distinct genetic clusters were detected within the Satilla River juvenile collection, along with two clusters within the Edisto River sample. In F1ST and FST analyses, the extent of the pairwise genetic differentiation between the two genetic clusters in the Ogeechee River and the three in the Satilla River was greater than that between all other pairwise comparisons among rivers in the South Atlantic DPS. In contrast, we found no evidence of the genetic partitioning of juvenile sturgeon within the neighboring Savannah or Altamaha river populations. Using IBA, we found that the overall Ogeechee River population made a moderate contribution (8.3%) to the overall mixed-stock collections (n = 1512) from coastal North Carolina to the Bay of Fundy. Surprisingly, all of the Ogeechee River-assigned specimens (n = 125) in these mixed-stock aggregations were representatives of only one of the two Ogeechee River genetic clusters. These results suggest that the two Ogeechee River genetic clusters exhibit significantly different life history strategies, with one being resident and the second being highly migratory.

Polychlorinated biphenyls (PCBs) cause significant health and reproductive problems in many vertebrates. Exposure during embryogenesis likely leads to defects in organ development, compromising survival and growth through adulthood. The present study identifies the impact of PCBs on the embryonic development of key organs and resulting consequences on survival and growth. Zebrafish embryos were treated with individual PCB congeners (126 or 104) or one of 4 Aroclor mixtures (1016, 1242, 1254, or 1260) and analyzed for changes in gross embryonic morphology. Specific organs were assessed for defects during embryonic development, using a variety of transgenic zebrafish to improve organ visualization. Resulting larvae were grown to adulthood while survival and growth were assayed. Embryonic gross development on PCB treatment was abnormal, with defects presenting in a concentration-dependent manner in the liver, pancreas, heart, and blood vessel organization. Polychlorinated biphenyl 126 treatment resulted in the most consistently severe and fatal phenotypes, whereas treatments with PCB 104 and Aroclors resulted in a range of more subtle organ defects. Survival of fish was highly variable although the growth rates of surviving fish were relatively normal, suggesting that maturing PCB-treated fish that survive develop compensatory strategies needed to reach adulthood. Life span analyses of fish from embryogenesis through adulthood, as in the present study, are scarce but important for the field because they help identify foci for further studies. Environ Toxicol Chem 2021;40:187-201. © 2020 SETAC.

Sturgeon populations worldwide are threatened with extirpation but little is known about their tendency to bioaccumulate contaminants and their sensitivities to environmental burdens of these contaminants. Shortnose sturgeon and Atlantic sturgeon, two species that are federally endangered in the USA, co-occur in the Hudson River (HR) where high sediment levels of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzo-p-furans (PCDFs) occur. Previous controlled laboratory studies showed that young life-stages of both species are sensitive to toxicities at low levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and PCB126 exposure. The objective here was to measure congener-specific hepatic levels of PCBs and PCDD/Fs in HR specimens in order to determine if in situ bioaccumulation of these compounds is sufficiently high to have caused the early life-stage toxicities previously observed. Estimates of hepatic burdens of PCBs and PCDD/Fs were obtained from a small number of specimens of each species collected between 2014 and 2016 and specimens of shortnose sturgeon collected over 30 years earlier and archived in a museum collection. Several significant patterns emerged. Hepatic levels of legacy PCBs and PCDDs were low in specimens of both species but typically higher in shortnose than Atlantic sturgeon, a pattern consistent with their habitat use in the HR. Hepatic burdens in shortnose sturgeon tended to be higher in archived specimens than in more recently collected ones despite expected reduction in archived specimens due to preservation methods. Several inadvertent PCBs congeners were detected at high levels, including PCB11, but their toxicity to natural populations remains unknown. Levels of select PCDFs congeners, 2,3,7,8-TCDF and 2,3,4,7,8 PeCDF, were elevated in some shortnose sturgeon individuals from the HR. Using Relative Potency (ReP) factors derived from white sturgeon, the observed levels of some hepatic PCDFs in HR shortnose sturgeon may have been sufficiently high to impair recruitment of young life-stages in this ecosystem.

Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) is an anadromous fish of considerable conservation concern, following its long history of overfishing and exposure to a variety of other anthropogenic stressors. Though reaching a large size, population abundances (Nc) of Atlantic sturgeon are not easily surveyed using traditional fishery methods because of their relative scarcity and their many age classes, often exhibiting extensive and differential movements that render them not readily amenable to traditional sampling efforts. A metric of their vulnerability to inbreeding and a possible alternative to Nc for abundance monitoring is effective population size (Ne). We surveyed 14 Atlantic sturgeon populations across their range using a suite of DNA microsatellite markers. Contemporary levels of Ne ranged from 1 in the St. Marys River, Florida–Georgia, to 156 in the Hudson River, New York. Historical Ne estimates averaged about 11.5 × higher than contemporary estimates, with a high of 927 for the Kennebec River population. Because of a mix of life history characteristics that make traditional Ne estimates based on imperfectly mixed year classes of juveniles questionable, we propose and provide results of a new, more robust and diagnostic approach based on sequential cohorts, termed Ne Max. Although contemporary Ne values obtained were at levels that might be considered troublesome, we suggest that the unique life history factors of this species may render it more resistant than other taxa to inbreeding effects. Because of the many differences among populations in size, age, and sex ratio and in harvest histories, we do not believe that a reliable extrapolation factor between Ne and Nc is yet possible. However, ongoing monitoring of Ne and Nc in populations might be sensitive to population changes and could form the basis of determining a relationship between Ne and Nc.

Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus is listed under the U.S. Endangered Species Act as five Distinct Population Segments (DPS). Subadult Atlantic Sturgeon are highly migratory in coastal waters and often move to non-natal estuaries where they encounter a variety of anthropogenic disturbances that may compromise their survival. The Hudson River estuary hosts large numbers of subadult Atlantic Sturgeon seasonally, but their DPS and population origin is unknown. We used microsatellite DNA analysis at 11 loci and sequence analysis of the mitochondrial DNA control region in Individual Based Assignment testing to determine the origin of 148 subadult Atlantic Sturgeon that were collected in the tidal Hudson River estuary between river kilometers (RKM)5 and RKM 124 north of the Battery in New York City (RKM 0). We also determined the origin of eight dead specimens (subadults and adults) that were likely victims of vessel strikes and found floating between RKM27 and RKM60. We determined that 142 of 148 subadults assigned to the Hudson River (New York Bight DPS), the vast majority (138 of 142) with at least 95%, and usually, 100%, probability. All eight dead specimens assigned to the Hudson River with greater than 99% probability. Of the six subadult specimens that did not assign to the Hudson, two each assigned to the Kennebec River (Gulf of Maine DPS) and Delaware River (New York Bight DPS), one to the Ogeechee River (South Atlantic DPS), and one to the James River (Chesapeake Bay DPS). Our analysis allows the effects of anthropogenic threats in the Hudson River to be apportioned to the DPS and natal river populations of Atlantic Sturgeon found there and serves as a model for genetic population composition analysis for subadult Atlantic Sturgeon in other impacted estuaries.

Background Application of Social Network Analysis (SNA) to acoustic telemetry is a useful approach to examine social behavior in fish. Atlantic Sturgeon (Acipenser oxyrinchus oxyrinchus) are ancient, long-lived anadromous finfish. Although Atlantic Sturgeon have been the subject of numerous telemetry studies, none have used SNA to analyze their co-occurrence behavior. During 2010–2014 Atlantic Sturgeon (n = 103) that were later genetically identified as being from the Saint John River, Canada and the Kennebec River, US were captured by otter trawl and brush weir in Minas Basin, Bay of Fundy, Canada, and acoustically tagged. Using data from moored acoustic receivers within foraging habitat in Minas Basin, we tested if Atlantic Sturgeon formed social associations that were random or structured during 2012 to 2014; and whether these co-occurrences consisted of individuals from the same river of origin or capture date. Results Irrespective of genetic origin and initial capture date, Atlantic Sturgeon formed co-occurrences in Minas Basin that were significantly different than would be observed by chance during 2012 and very close to significant during 2013. Analysis demonstrated that some Atlantic Sturgeon preferentially co-occur within their primary feeding habitat. Conclusions The current threats to Atlantic Sturgeon aggregations within the Bay of Fundy, Nova Scotia, include bycatch in fisheries throughout their coastal migration routes and more recently the development of tidal turbines along their migratory corridor to their summer aggregation site. It is important to determine if Atlantic Sturgeon form aggregations with conspecifics from the same population to inform management decisions regarding threats to groups of individuals. This study indicated that Atlantic Sturgeon may form preferential co-occurrences within their feeding aggregation and co-occurrences that were identified were not dependent upon population of origin or initial capture date.

Atlantic sturgeon Acipenser oxyrinchus surfacing behaviour was investigated in Minas Basin (45° 20' N; 64° 00' W) and the Bay of Fundy with pop-up satellite archival tags (MiniPAT) measuring physical variables (pressure, temperature, light). Of six tags deployed during June and July, five provided pop-up locations and two were recovered after c. 4 months. Analysis of recovered archival data revealed that the frequency of surfacing events was highest (78·9%) when A. oxyrinchus were in Minas Basin at depths 40 m). The tidal cycle in Minas Basin had a significant relationship to surfacing frequency, with the most surfacing events (49·5%) occurring on the flood tide, from mid- to high-tide. Surfacing events ranged from 0-12 a day and the maximum number occurred between 2300 and 0300 hours. Maximum surfacing ascent speeds ranged from 0·50 to 4·17 m s-1 and maximum descent speeds ranged from 0·17 to 3·17 m s-1 . Buoyancy control, by gulping air to inflate the gas bladder, is proposed as the main reason for surfacing behaviour in A. oxyrinchus.

Rapid evolution of pest, pathogen, and wildlife populations can have undesirable effects, for example, when insects evolve resistance to pesticides or fishes evolve smaller body size in response to harvest. A destructive invasive species in the Laurentian Great Lakes, the sea lamprey (Petromyzon marinus) has been controlled with the pesticide 3-trifluoromethyl-4-nitrophenol (TFM) since the 1950s. We evaluated the likelihood of sea lamprey evolving resistance to TFM by (i) reviewing sea lamprey life history and control; (ii) identifying physiological and behavioural resistance strategies; (iii) estimating the strength of selection from TFM; (iv) assessing the timeline for evolution; and (v) analyzing historical toxicity data for evidence of resistance. The number of sea lamprey generations exposed to TFM was within the range observed for fish populations where rapid evolution has occurred. Mortality from TFM was estimated as 82%–90%, suggesting significant selective pressure. However, 57 years of toxicity data revealed no increase in lethal concentrations of TFM. Vigilance and the development of alternative controls are required to prevent this aquatic invasive species from evolving strategies to evade control.

Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) is an endangered species that migrate through, and occupy the coastal waters of the mid-Atlantic Bight where they interact with anthropogenic activities. Measures to understand and avoid Atlantic sturgeon that take into consideration the dynamic nature of their habitat may reduce harmful interactions. In this study, we matched fisheries independent biotelemetry observations of Atlantic sturgeon with daily satellite observations to construct a time resolved spatial distribution model of Atlantic sturgeon. We determined that depth, day-of-year, sea surface temperature, and light absorption by seawater were the most important predictors of Atlantic sturgeon occurrence. Demographic factors, such as sex and river-of-origin were of secondary importance. We found strong spatial differences in spring and fall migration patterns, when anthropogenic interactions peak. Our cross-validated models correctly identified > 88% of biotelemetry observations in our study region. Our models also correctly identified ∼64% of bycatch observations throughout the year. However, during their migrations, when harmful interactions were highest, our models correctly identified ∼90% of fisheries dependent observations. We suggest that this model can be used for guidance to managers and stakeholders to reduce interactions with this highly imperiled species, thereby enhancing conservation and recovery efforts.

Natural mortality of Atlantic sturgeon (Acipenser oxyrinchus) has been determined to be low (M = 0.07). Reported herein is the mortality by beach stranding of 11 Atlantic sturgeon in Scot's Bay, part of the inner Bay of Fundy in Nova Scotia, Canada on 22 June 2014. Genetic analyses, histological analysis and age determination were performed to determine origin, maturity stage and age of the stranded Atlantic sturgeon. Microsatellite and mitochondrial DNA analyses indicated that four of the Atlantic sturgeon (2 males and 2 females) were from the Saint John River, NB population, which was designated as threatened by the Committee on the Status of Endangered Wildlife in Canada. Seven Atlantic sturgeon (1 male, 5 females, 1 unknown) were from the Kennebec River, Maine population, that was listed as threatened under the Endangered Species Act in the U. S. Ageing of A. oxyrinchus by pectoral fin spine analysis determined that the mean age of the individuals from the Saint John River ( [Formula: see text] years, sd = 5.0) and the Kennebec River ( [Formula: see text] years, sd = 3.5) were not significantly different. This is the first report of a stranding event of Atlantic sturgeon, and describes a source of natural mortality affecting populations of concern in both Canada and the U. S.

Phragmites australis is a perennial grass that has invaded wetlands of the northeastern United States over the past century. The Hudson River Estuary and surrounding watersheds are no exception in that populations of P. australis have spread dramatically along its shores and tributaries in the past 40 years. Recent studies have shown that genetically variable populations of P. australis can spread by seed dispersal in addition to clonal mechanisms. It is important to characterize the genetic variation of Hudson River populations as part of a management strategy for this species to determine the mechanisms by which its spreads and colonizes new habitats, particularly those with frequent anthropogenic disturbances. The goals of this study were to quantify levels of genetic variation and structuring in Hudson River populations of P. australis using microsatellite DNA analysis. A total of 354 culms of P. australis were collected from nine locations ranging from Albany, New York to Staten Island, New York in the summers of 2004 (N = 174) and 2011 (N = 180). Microsatellite data from eight loci indicated that the Hudson River Estuary has some of the highest levels of genetic variation of all U. S. Atlantic Coast regions containing P. australis. Gene diversity (Hs) across all loci in the 2004 collection was 0.45 (±0.02) and that of the 2011 collection was 0.47 (±0.07). Patches within sample sites were rarely monoclonal and had multiple genetic phenotypes. Moran’s Identity tests indicated that individuals within a patch were closely related, whereas little genetic relatedness was evident among individuals from sample sites >1 km apart. Spatial structuring was also not evident in autospatial correlation and principle coordinate analyses. These findings suggest that genetic diversity is maintained within stands by sexual reproduction and that seeds are important in dispersal of P. australis across the Hudson River Estuary. Ample habitats are available for establishment of new Phragmites stands due to high levels of anthropogenic disturbance from populations living along the Estuary. Wildlife managers should focus on monitoring habitats that provide seedbed for Phragmites and promote land use practices that prevent soil disturbance and establishment of new stands.

Sturgeon species are imperiled world-wide by a variety of anthropogenic stressors including chemical contaminants. Atlantic sturgeon, Acipenser oxyrinchus, and shortnose sturgeon, Acipenser brevirostrum, are largely sympatric acipenserids whose young life-stages are often exposed to high levels of benthic-borne PCBs and PCDD/Fs in large estuaries along the Atlantic Coast of North America. In previous laboratory studies, we demonstrated that both sturgeon species are sensitive to early life-stage toxicities from exposure to environmentally relevant concentrations of coplanar PCBs and TCDD. The sensitivity of young life-stages of fishes to these contaminants varies among species by three orders of magnitude and often is due to variation in the structure and function of the aryl hydrocarbon receptor (AHR) pathway. Unlike mammals, fishes have two forms of AHR (AHR1 and AHR2) with AHR2 usually being more highly expressed across tissues and functional in mediating toxicities. Based on previous studies in white sturgeon, A. transmontanus, we hypothesized that sturgeon taxa are unusually sensitive to these contaminants because of higher levels of expression and functional activity of AHR1 than in other fish taxa. To address this possibility, we characterized AHR1 in both Atlantic Coast sturgeon species, evaluated its' in vivo expression in young life-stages and in multiple tissues of shortnose sturgeon, and tested its ability to drive reporter gene expression in AHR-deficient cells treated with graded doses of PCB126 and TCDD. Similar to white sturgeon and lake sturgeon, AHR1 amino acid sequences in Atlantic sturgeon and shortnose sturgeon were more similar to mammalian AHRs and avian AHR1s than to AHR1 in other fishes, suggesting their greater functionality in sturgeon species than in other fishes. Exposure to graded doses of coplanar PCBs and TCDD usually failed to significantly induce AHR1 expression in young life-stages or most tissues of shortnose sturgeon. However, in reporter gene assays, AHR1 drove higher levels of gene expression than AHR2 alone, but their binary combination failed to drive higher levels of expression than either AHR alone. In total, our results suggest that AHR1 may be more functional in sturgeon species than in other fishes, but probably does not explain their heightened sensitivity to these contaminants.

Atlantic sturgeon and shortnose sturgeon co-occur in many estuaries along the Atlantic Coast of North America. Both species are protected under the U.S. Endangered Species Act and internationally on the IUCN Red list and by CITES. Early life-stages of both sturgeons may be exposed to persistent aromatic hydrocarbon contaminants such as PCBs and PCDD/Fs which are at high levels in the sediments of impacted spawning rivers. Our objective was to compare the PCBs and TCDD sensitivities of both species with those of other fishes and to determine if environmental concentrations of these contaminants approach those that induce toxicity to their young life-stages under controlled laboratory conditions. Because our previous studies suggested that young life-stages of North American sturgeons are among the more sensitive of fishes to coplanar PCB and TCDD-induced toxicities, we were interested in identifying the molecular bases of this vulnerability. It is known that activation of the aryl hydrocarbon receptor 2 (AHR2) in fishes mediates most toxicities to these contaminants and transcriptional activation of xenobiotic metabolizing enzymes such as cytochrome P4501A (CYP1A). Previous studies demonstrated that structural and functional variations in AHRs are the bases for differing sensitivities of several vertebrate taxa to aromatic hydrocarbons. Therefore, in this study we characterized AHR2 and its expression in both sturgeons as an initial step in understanding the mechanistic bases of their sensitivities to these contaminants. We also used CYP1A expression as an endpoint to develop Toxicity Equivalency Factors (TEFs) for these sturgeons. We found that critical amino acid residues in the ligand binding domain of AHR2 in both sturgeons were identical to those of the aromatic hydrocarbon-sensitive white sturgeon, and differed from the less sensitive lake sturgeon. AHR2 expression was induced by TCDD (up to 6-fold) and by three of four tested coplanar PCB congeners (3–5-fold) in Atlantic sturgeon, but less so in shortnose sturgeon. We found that expression of AHR2 and CYP1A mRNA significantly covaried after exposure to TCDD and PCB77, PCB81, PCB126, but not PCB169 in both sturgeons. We also determined TEFs for the four coplanar PCBs in shortnose sturgeon based on comparison of CYP1A mRNA expression across all doses. Surprisingly, the TEFs for all four coplanar PCBs in shortnose sturgeon were much higher (6.4–162 times) than previously adopted for fishes by the WHO.

Microsatellite DNA and mitochondrial DNA control-region sequence analyses were used to determine the population and distinct population segment (DPS) origin of 173 Atlantic sturgeon Acipenser oxyrinchus oxyrinchus encountered from the Gulf of Maine to Cape Hatteras, North Carolina, in NOAA’s Northeast Fisheries Observer Program. It was found that the Hudson River was by far the greatest contributor to this coastal by-catch, with 42 ⋅2–46 ⋅3% of specimens originating there. Generally, specimens represented the geographic province of the river in which they were spawned, but some specimens, particularly those originating in the South Atlantic DPS, moved to great distances. Genetic mixed-stock analyses provide an accurate approach to determine the DPS and population origin of A. o. oxyrinchus by-catch in coastal waters, but most informative management requires that these results be partitioned by locale, season, target fishery and gear type.

Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus was federally listed under the U.S. Endangered Species Act as five distinct population segments (DPS). Currently, at least 18 estuaries coastwide host spawning populations and the viability of these vary, requiring differing levels of protection. Subadults emigrate from their natal estuaries to marine waters where they are vulnerable to bycatch; one of the major threats to the rebuilding of populations. As a result, identifying the population origin of Atlantic Sturgeon in coastal waters is critical to development of management plans intended to minimize interactions of the most imperiled populations with damaging fisheries. We used mitochondrial DNA control region sequencing and microsatellite DNA analyses to determine the origin of 261 Atlantic Sturgeon collected off the Delaware coast during the spring months. Using individual-based assignment (IBA) testing and mixed stock analysis, we found that specimens originated from all nine of our referen...

American Shad Alosa sapidissima in the Hudson River, New York, and coastwide have shown major long-term declines. A possible contributing factor is commercial fisheries that harvest this population outside of the Hudson River estuary. Using previously published and new reference microsatellite data from 33 baseline populations, our goals were (1) to estimate the proportion of Hudson River American Shad contributing to the two remaining major mixed-stock fisheries along the Atlantic coast in Delaware Bay and the Bay of Fundy and (2) to estimate the proportions of other American Shad stocks contributing to these two fisheries at the highest level of stock specificity. Stock composition estimates for 2009 and 2010 Delaware Bay collections were made using three models that ranged from the most simple question (Hudson River and Delaware Bay populations) to one with all 33 baseline populations included. In all cases, a Hudson River contribution nearly equal to that of the Delaware Bay contribution w...

Many Winter Flounder Pseudopleuronectes americanus populations have declined dramatically. In U.S. waters, Winter Flounder are managed as three stocks: Gulf of Maine, southern New England–Mid-Atlantic Bight, and Georges Bank. Historically, it was believed that the spawning of inshore stocks occurs exclusively within natal estuaries. Based on the supposition of estuary-specific spawning, we hypothesized that Winter Flounder exhibit greater stock structure than predicted by the three-stock model and, in fact, that they exhibit genetic differentiation at the level of individual estuaries. We tested this hypothesis by conducting microsatellite DNA analysis at 12 loci and single-nucleotide polymorphism analysis at 4 loci on young-of-the year and adult Winter Flounder collected from 27 estuaries from Newfoundland to Delaware as well as from Georges Bank. We found highly significant coastwide genetic stock structure among Winter Flounder; however, there was little evidence of estuary-specific structure. ...

The Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus is 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

Five 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 microsate...

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. Environ. Toxicol. Chem. 2012; 31: 2324–2337. © 2012 SETAC

Summary Most larger individuals of migratory striped bass Morone saxatilis from the two major Atlantic coast stocks, the Chesapeake Bay and Hudson River, appear to winter in mid-Atlantic coastal waters. But it is not known whether they exhibit differential wintertime distributions in accordance with the latitudinal differences in locations of these two estuaries. Mixed-stock analyses were conducted based on mitochondrial DNA and nuclear DNA genotypic frequencies on wintertime collections of striped bass from coastal waters. No significant differences (P > 0.05) were seen in the proportions of striped bass from the two stocks between collections made from the Delaware Bay mouth and Cape Hatteras in 1997. However, there was a substantially higher Hudson contribution to a 1995 collection from coastal New Jersey (0.349, SD = 0.136) than to the combined 1997 Delaware Bay mouth and Cape Hatteras collection (0.157, SD = 0.072), suggesting this question deserves further study. Additionally, use of the original four reference samples from Chesapeake Bay tributaries (Choptank, Potomac, Rappahannock, Upper Bay) proved adequate alone in characterizing the Chesapeake Bay stock in simulations in which additional tributary collections (Nanticoke, Patuxent, Pocomoke) were added.

The mechanistic basis of resistance of vertebrate populations to contaminants, including Atlantic tomcod from the Hudson River (HR) to polychlorinated biphenyls (PCBs), is unknown. HR tomcod exhibited variants in the aryl hydrocarbon receptor 2 (AHR2) that were nearly absent elsewhere. In ligand-binding assays, AHR2-1 protein (common in the HR) was impaired as compared to widespread AHR2-2 in binding TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) and in driving expression in reporter gene assays in AHR-deficient cells treated with TCDD or PCB126. We identified a six-base deletion in AHR2 as the basis of resistance and suggest that the HR population has undergone rapid evolution, probably due to contaminant exposure. This mechanistic basis of resistance in a vertebrate population provides evidence of evolutionary change due to selective pressure at a single locus.

Atlantic cod Gadus morhua in US waters are currently managed as 2 stocks: (1) a Gulf of Maine stock and (2) a Georges Bank and south stock. This designation is decades old and warrants re-evaluation in light of concerns that fisheries management units may not reflect biologically mean- ingful population units. In this study, we used 10 microsatellite loci, the PanI locus, and 5 single nucleotide polymorphism markers to characterize the population genetic structure of cod in US waters. We found significant differentiation among temporally and spatially divergent populations of cod (global FST = 0.0044), primarily stemming from 2 potentially non-neutral loci, and evidence for a population structure that strongly contradicts the current 2-stock management model. This genetic structure was stable over a 5 yr period. Our results indicate that cod in US waters are broadly struc- tured into 3 groups: (1) a northern spring-spawning coastal complex in the Gulf of Maine (GOM), (2) a southern complex consisting of winter-spawning inshore GOM, offshore GOM and sites south of Cape Cod, Massachusetts, and (3) a Georges Bank population. The strongest differentiation occurs between populations in the northern and southern complex (mean FST = 0.0085), some of which spawn in the same bays in different seasons. By means of mixture analysis, young-of-the-year fish sampled on juvenile nurseries were assigned to the spawning complex of their origin. Our findings contribute to a growing body of knowledge that Atlantic cod and other marine fish populations are structured on a finer scale than previously thought and that this structure supports biocomplexity and locally adapted populations. As such, it may be warranted to re-evaluate current management units and tailor management plans toward this finer scale.

Whether sea lampreys Petromyzon marinus are native to Lake Ontario (and Lake Champlain) has been vigorously argued for more than half a century. In earlier decades, this debate was restricted to su...

The distribution of natural populations of American mink is restricted to locales that are in proximity to aquatic ecosystems. Because of the lipophilicity and persistence of polychlorinated biphenyls (PCBs) and reliance of mink on aquatic-based diets, mink at contaminated locales often bioacccumulate high levels of PCBs. In addition, in controlled laboratory studies, mink are highly sensitive at reproductive and developmental end points to the toxic effects of environmental PCB mixtures. It is believed that most, if not all, toxic effects of PCBs occur through activation of the aryl hydrocarbon receptor (AHR) pathway. Transcription of cytochrome P4501A1 (CYP1A1) by PCBs is also mediated through activation of AHR. Thus, levels of CYP1A1 mRNA provide a quantitative assay of exposure to and early biologic effect of PCBs on mink and may be predictive of toxicity at higher levels of biologic organization. We developed polymerase chain reaction (PCR) primers to amplify CYP1A1 as well as identified a housekeeping gene from mink cDNA. We used real-time reverse transcription-PCR to quantify and compare levels of hepatic CYP1A mRNA among groups of ranched mink kits and juveniles, which were fed diets or exposed in utero to fish that were low in PCBs (Atlantic herring) or to diets that were contaminated with three different levels of PCBs (carp) from Saginaw Bay, Lake Michigan. We found significant differences in CYP1A1 mRNA expression between mink fed the control diet and those fed a PCB-contaminated carp diet at all three treatment levels and exposure times. CYP1A1 mRNA was significantly induced 5.3- to 6.6-fold and 3.7- to 4.7-fold at 6 and 27 weeks, respectively. In previous studies, dietary exposures to PCB-contaminated carp were shown to cause mild to moderate lesions in the mandible and maxilla of these animals. This study demonstrates that hepatic CYP1A1 mRNA may be a sensitive biomarker of exposure of mink to environmentally relevant levels of PCBs and may be predictive of their effects in natural populations.

Shortnose sturgeon Acipenser brevirostrum is federally listed as ‘‘an endangered species threatened with extinction’’ in the U.S. but its listing status is currently under review. As part of this process, the U.S. National Marine Fisheries Service will determine if shortnose sturgeon are divided into Distinct Population Segments (DPS) across its distribution. In this regard, we sought to determine if shortnose sturgeon occur in genetically “discrete population segments,” and if so, the boundaries of each. We used mitochondrial DNA (mtDNA) control region sequence analysis to assess the genetic discreteness of 14 of 19 river populations that were recommended as DPS in the 1998 Final Recovery Plan for Shortnose Sturgeon. Nine of the 14 proposed DPS proved significantly discrete (P < 0.05 after Bonferoni correction) from both of their bracketing populations, the exceptions being those in the Penobscot River, Chesapeake Bay, Cooper River, and Ogeechee River (our sample from the Cape Fear River was insufficient to statistically analyze). Haplotype frequencies in the newly “rediscovered” Penobscot River collection were almost identical to those in the proximal Kennebec River system. Genetic data in combination with tagging results suggest that shortnose sturgeon in the Penobscot River are probably migrants from the Kennebec. Likewise, shortnose sturgeon found today within the Chesapeake Bay appear to be migrants from the Delaware River. While haplotype frequencies in the remnant Santee River population in Lake Marion differed significantly from those in nearby Winyah Bay, they did not differ significantly from those in the Cooper River. This suggests that the Cooper River harbors descendants of the Santee River population that are unable to access their historical spawning locales. The Ogeechee River collection was not genetically distinct from that in the nearby Savannah River, suggesting that it may host descendants of hatchery-reared individuals of Savannah River ancestry. Our genetic results indicate that most, but not all, rivers with shortnose sturgeon host genetically discrete populations, constituting important information in the consideration of DPS designations. However, shortnose sturgeon migrations through coastal waters to proximal rivers and release of hatchery-reared fish may confound results from genetic studies such as ours and lead to the possible misidentification of discrete population segments.

There is considerable interest in restoring stocks of Atlantic sturgeon (Acipenser oxyrinchus), one of only two dozen extant sturgeons worldwide. Populations of its two subspecies are found in large rivers along the North American coasts of the Atlantic (A. o. oxyrinchus) and the Gulf of Mexico (A. o. desotoi). Although these populations were severely reduced because of overfishing and, in some instances, blockage of spawning runs, their present statuses vary from those that still support limited fisheries (St. John River, New Brunswick), to a large but apparently declining population (Hudson River), to relict-sized (Delaware River, Mobile River), to apparently extirpated (Maryland tributaries of Chesapeake Bay; St. Johns River, Florida). There are two primary alternatives for restoring these populations: (1) eliminating harvest and allowing natural recolonization and increase and (2) hatchery-based stocking (reintroduction or supplementation). We performed genetic analyses aimed at guiding restoration efforts. Mitochondrial DNA analysis revealed strong stock structure along both coasts at the regional and, in some instances, population levels. Estimates of gene flow rates were low and suggested slow natural recolonization rates. Thus, the first alternative avoids the genetic risks of interstock transfer and inbreeding depression that may result from hatchery-based programs, but given the low intrinsic rates of increase and recolonization of Atlantic sturgeon, recovery may take decades to centuries, if it occurs at all. Therefore, it is imperative that the restoration approach be tailored to the particular circumstances and demographics of each population; however, the characteristics of this species and poor funding prospects make this information difficult to obtain. It appears likely that initial Atlantic sturgeon stocking efforts will target systems where they are extinct, as recently occurred in the Nanticoke River of Chesapeake Bay. Estatus y Opciones de Restauracion Para el Esturion del Atlantico en Norteamerica Existe un interes considerable en la restauracion e poblaciones del esturion del Atlantico (Acipenser oxyrinchus), una de las doce especies de esturiones existentes a nivel mundial. Las poblaciones de sus dos subespecies se encuentran en rios grandes a lo largo de las costas del Atlantico (A.o. oxyrinchus) y el Golfo de Mexico (A.o. desoti) en Norteamerica. Aunque estas poblaciones fueron serveramente reducidas debido a la sobrepesca y en algunos casos al bloqueo de las corridas de desove, su estatus actual varia desde aquellas poblaciones que aun soportan pesquerias limitadas (i.e. rio Saint John, New Brunswick), poblaciones grandes pero aparentemente en declive (rio Hudson), hasta poblaciones-relicto (rio Delaware, rio Monile) o poblaciones aparentemente extirpadas (tributarios de Maryland de la Bahia Chesapeake; rio Saint Johns, Florida). Existen dos alternativas principales para restablecer estas poblaciones: (1) eliminando la cosecha y permitiendo la recolonizacion natural y el incremento y (2) soporte basado en granjas (reintroduccion o suplementacion). Realizamos un analisis genetico tratando de establecer guias para los esfuerzos de restauracion. El analisis de ADN mitocondrial revela una fuerte estructura de grupos a lo largo de las costas de la region y en algunos casos a nivel de especificidad poblacional. Las estimaciones de las tasas de flujo genetico fueron bajas y sugieren tasas de recolonizacion bajas. Por lo tanto, la primera alternativa evita los riesgos geneticos de transferencia intrapoblacional y la depresion por intracruza que podria resultar de los programas basados en granjas, pero dadas las bajas tasas intrinsecas de incremento y recolonizacion del esturion del Atlantico, la recuperacion podria tomar decadas, en caso de que ocurriera. Es por ello, que es imperativo que los intentos de restauracion se apeguen a las circunstancias particulares y demograficas de cada poblacion, sin embargo, las caracteristicas de la especie y los pobres prospectos de financiamiento hacen esta informacion dificil de obtener. Aparentemente los esfuerzos iniciales para repoblar poblaciones de esturion del Atlantico deberan enfocarse en sistemas donde los esturiones han sido extinguidos como ha ocurrido recientemente en el rio Nanticoke de la bahia Chesapeake.

Summary There are nine acipenseriform species in North America: two on the Pacific Coast, two on the Atlantic Coast, and five purely freshwater forms. Six of these species are subject to commercial harvest and three to aquaculture. The North American sturgeon and paddlefish meat and caviar marketplace is comprised of legally and illegally acquired products from wild and captive populations of indigenous species as well as non-indigenous species from import and/or culture. Overall, at least 11 species can legally occur in the market. Future aquaculture development will most certainly increase this number. Some indigenous species subject to commercial harvest or culture are under partial or complete range protection, adding another layer of monitoring complexity at the population specific level. We identify four primary levels of confusion in the identification of caviar from North American acipenseriforms in North America: among North American species, among populations within a North American species, between wild and farmed specimens of a North American species, and between North American and imported non-North American species. This complexity reveals the need for additional research into forensic tools, species boundaries and population structure if effective enforcement of harvest and market restrictions is to ensue. For species not subject to commercial harvest and trade, research is needed to identify illegal products from the species.

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...

To evaluate the associations of breast cancer risk with polymorphisms in the XPC and XPD/ERCC2 DNA nucleotide excision repair genes, a case-control study nested within a prospective cohort of 14,274 women was conducted. Genotypes were characterized for 612 incident, invasive breast cancer cases and their 1:1 matched controls. The homozygous variant of a poly(AT) insertion/deletion polymorphism in intron 9 of the XPC gene (XPC-PAT+/+), was associated with breast cancer risk [odds ratio (OR) = 1.45, 95% confidence interval: 1.07-1.97], after adjustment for other breast cancer risk factors. The breast cancer risk associated with XPC-PAT+/+ did not differ by age at diagnosis. There was an indication of an interaction (p = 0.08) between the XPC-PAT+/+ genotype and cigarette smoking. Ever smokers with the XPC-PAT+/+ genotype were at elevated risk of breast cancer (OR = 1.56, CI: 0.95-2.58), but no differences were observed among never smokers. Analyses of the ERCC2 Lys751Gln polymorphism did not show an association with breast cancer risk, either overall or at younger ages. The results suggest that breast cancer risk is related to the XPC haplotype tagged by the XPC-PAT+/+ insertion-deletion polymorphism in intron 9. Further study of the XPC haplotypes and their interactions with smoking in relation to breast cancer risk is needed.

The Atlantic sturgeon Acipenser oxyrinchus oxyrinchus is a highly migratory anadromous acipenserid that is distributed along the Atlantic coast of North America. The abundance of Atlantic sturgeon has not increased appreciably in recent years despite the imposition of a moratorium on its harvest in U.S. waters in 1998. Two measures being considered to restore depleted or extirpated populations are designation of Atlantic sturgeon as federally endangered under the U.S. Endangered Species Act and the use of hatchery-reared fish to supplement natural reproduction. Implementation of these approaches requires detailed knowledge of this species' population structure. Previous genetic stock identification studies failed to address the discreteness of Atlantic sturgeon populations along the U.S. mid-Atlantic coast that historically supported two of the largest fisheries for the species. We used mitochondrial DNA (mtDNA) control region sequence data to elucidate the population structure of Atlantic sturge...

The anadromous Atlantic sturgeon Acipenser oxyrinchus oxyrinchus, a wide-ranging species along the Atlantic Coast of North America, is being considered for federal listing under the U.S. Endangered Species Act. Identification of distinct population segments (DPS) is necessary but problematic for highly vagile species such as Atlantic sturgeon which may spend a high proportion of their lives outside of their natal estuaries. Characterization of genetic differentiation and estimates of gene flow provide a quantitative measure of the number of DPS into which species could be divided over their distribution and the reproductive independence of each unit. We sequenced a portion of the mitochondrial DNA control region to characterize population structure and gene flow across all naturally reproducing populations from which specimens could be obtained. We then considered these genetic data along with ancillary information on life history characteristics, historical fisheries data, and trajectories of abundance to determine the number of DPS into which this species should be divided. Our results suggest that philopatry is high for Atlantic sturgeon and that each U.S. estuary analyzed hosts genetically distinct populations of Atlantic sturgeon. We conclude that at least nine DPS of Atlantic sturgeon exist along the Atlantic Coast of the U.S. In contrast, the Atlantic Sturgeon Status Review Team has proposed a five DPS scheme for this subspecies based largely on results from nuclear DNA microsatellites, but with fewer populations represented and lower samples sizes. These different conclusions illustrate the somewhat arbitrary nature of the DPS concept, at least as applied to Atlantic sturgeon.

Management of Atlantic cod Gadus morhua in U.S. waters is based on a two-stock model composed of stocks from (1) the Gulf of Maine (GOM) and (2) Georges Bank (GB) and areas south; however, evidence suggests a more fine-scale structuring. We used microsatellite and single nucleotide polymorphism (SNP) analyses to investigate the stock structure of Atlantic cod in U.S. waters. In year 1, we analyzed microsatellite loci in larvae from GB, age-0 juveniles from multiple locations in the GOM, and adults of unknown maturity from GB, Jeffreys Ledge, and the Great South Channel (GSC). In year 2, Atlantic cod collected from spawning aggregations in Ipswich Bay in the spring and at GB, Stellwagen Bank, Chatham, and Ipswich Bay in the winter, along with adults of unknown maturity from Long Island, New York, were surveyed at a modified battery of microsatellites and three SNPs. In year 1, we saw no significant differences in allelic frequencies between our composite sample of adult and juvenile cod from the G...

Adult sea lampreys Petromyzon marinus parasitize a variety of recreationally, commercially, and ecologically important fishes in the north temperate Atlantic Ocean and some inland waters of North America, including the Great Lakes and Lake Champlain. This has resulted in the development of international, provincial, and state programs to suppress their abundance in some of these waters. This effort, in part, emanates from the nonnative status afforded sea lampreys in these lakes by management agencies. However, whether the sea lamprey is native to Lake Champlain has long been debated, and the outcome of this debate may impact the intensity of efforts to suppress their abundance there. We addressed this issue by using sequence analysis of the mitochondrial DNA control region. Resultant haplotype frequencies of sea lampreys from the Lake Champlain watershed were compared among sea lamprey collections made in multiple drainages within the Lake Ontario and Lake Superior watersheds and Atlantic coast ...

Atlantic tomcod Microgadus tomcod from the Hudson River, New York, are exposed to high levels of polycyclic aromatic hydrocarbons (PAHs) and bioaccumulate mixtures of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and polychlorinatedfurans (PCDD/Fs). Previous studies demonstrated that hepatic cytochrome P4501A (CYP1A) mRNA was not inducible in tomcod from the Hudson River treated with single doses of PCB77 or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), but was inducible with PAHs. In this study, we sought to determine if CYP1A mRNA was inducible with higher doses of these and other halogenated aromatic hydrocarbons (HAHs) in Hudson River tomcod and if decreased sensitivity to gene inducibility occurs across all tissues. Tomcod from the Hudson River and the cleaner Miramichi River, New Brunswick, were treated individually with graded doses of TCDD and coplanar PCBs (PCB77, PCB81, PCB126, PCB169) and profiles of hepatic CYP1A mRNA expression were compared between the two populations. CYP1A mRNA inducibility was also compared in multiple tissues of tomcod from the two rivers that were treated with PCB77. Additionally, hepatic CYP1A mRNA was characterized in Miramichi River tomcod treated with pairs of PCB congeners that included aryl hydrocarbon receptor (AHR) agonists and antagonists. Hepatic CYP1A mRNA was significantly inducible by all agonists in tomcod from the Miramichi River and TCDD and two of four PCBs in tomcod from the Hudson River. CYP1A mRNA was also significantly inducible in four of five tissues of tomcod from the Miramichi River but only in liver of Hudson River tomcod. In summary, CYP1A mRNA inducibility was approximately two orders of magnitude less sensitive in tomcod from the Hudson River than in those from the Miramichi River. But when achieved, maximum levels of CYP1A expression were similar in tomcod from the two populations. Co-administration of PCB126 and PCB77 did not produce significantly greater CYP1A mRNA induction than administration of PCB126 alone and co-administration of mono-ortho-substituted PCB105 significantly decreased CYP1A mRNA inducibility by PCB77. These results indicate that CYP1A mRNA expression is significantly inducible by HAHs in tomcod from the Hudson River and suggest that all components of the AHR pathway are present and functional, but that the pathway is less sensitive to activation than in tomcod from the Miramichi River. Our results also indicate that CYP1A mRNA levels in environmentally exposed fish may not reflect additive tissue burdens of PCB congeners.

Populations of organisms that are chronically exposed to high levels of chemical contaminants may not suffer the same sublethal or lethal effects as naive populations, a phenomenon called resistance. Atlantic tomcod (Microgadus tomcod) from the Hudson River, New York, are exposed to high concentrations of polycyclic aromatic hydrocarbons (PAHs) and bioaccumulate polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs). They have developed resistance to PCBs and PCDDs but not to PAHs. Resistance is largely heritable and manifests at early-life-stage toxic end points and in inducibility of cytochrome P4501A (CYP1A) mRNA expression. Because CYP1A induction is activated by the aryl hydrocarbon receptor (AHR) pathway, as are most toxic responses to these compounds, we sought to determine the geographic extent of resistance to CYP1A mRNA induction by PCBs in the Hudson River tomcod population. Samples of young-of-the-year tomcod were collected from seven locales in the Hudson River, extending from the Battery at river mile 1 (RM 1) to RM 90, and from the Miramichi River, New Brunswick, Canada. Laboratory-reared offspring of tomcod adults from Newark Bay, in the western portion of the Hudson River estuary, were also used in this study. Fish were partially depurated in clean water and intraperitoneally injected with 10 ppm coplanar PCB-77, 10 ppm benzo[a]pyrene (BaP), or corn oil vehicle, and levels of CYP1A mRNA were determined. CYP1A was significantly inducible by treatment with BaP in tomcod from the Miramichi River, from laboratory-spawned offspring of Newark Bay origin, and from all Hudson River sites spanning 90 miles of river. In contrast, only tomcod from the Miramichi River displayed significantly induced CYP1A mRNA expression when treated with PCB-77. Our results suggest that the population of tomcod from throughout the Hudson River estuary has developed resistance to CYP1A inducibility and probably other toxicities mediated by the AHR pathway. Tomcod from the Hudson River may represent the most geographically expansive population of vertebrates with resistance to chemical pollutants that has been characterized.

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.

Since the 1960s, only the Apalachicola–Chattahoochee–Flint (ACF) river system has continually supported a naturally reproducing population of striped bass Morone saxatilis of Gulf of Mexico (Gulf) lineage. Striped bass fry and fingerlings of Atlantic ancestry (from the Santee– Cooper system) were introduced into the ACF from the late 1960s to 1977. Genotypes were previously identified that were unique to fish from the ACF and that confirmed the continued natural reproduction of striped bass of Gulf ancestry within that population. Also, no significant difference in haplotype frequencies between “pure” archived ACF and extant ACF samples was found at an Xba I mitochondrial DNA (mtDNA) restriction site that is diagnostic in distinguishing extant ACF from extant Atlantic specimens. This suggested that significant maternally mediated introgression of Atlantic mtDNA genomes has not occurred. However, because mtDNA is maternally inherited, the introgression of paternally derived nuclear DNA alleles int...

Fish from urban and industrialized estuaries are exposed among the highest levels of contaminants of any vertebrate populations. As a result, they serve as especially relevant models for determining the toxic effects and mechanisms through which environmental toxicants work. In controlled laboratory experiments, fish from highly contaminated locales sometimes exhibit resistance to contaminant-induced toxicity. Resistance may be due to genetic adaptation or physiological acclimations. Distinguishing between these possibilities is important in predicting the persistence of resistance and its potential costs to affected populations and communities. Along the Atlantic coast of North America, populations of two estuarine species, Atlantic killifish (mummichog) Fundulus heteroclitus and Atlantic tomcod Microgadus tomcod, exhibit phenotypes that are resistant to aromatic hydrocarbon (AH) contaminants, including polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polycyclic aromatic hydrocarbons (PAHs). Populations of these species exhibit resistance to AH-induced lethality, early life-stage toxicities, and expression of cytochrome P4501A (CYP1A). However, some differences among populations in the occurrence and type (genetic or physiological) of AH-resistant phenotypes have been observed. In some instances, resistance was obviously genetic and resulted in its transmission to at least the F2 generation, in others, resistance had a physiological or yet to be identified epigenetic basis. In some cases, resistance was observed for all AH compounds tested, in others, it was seen only for halogenated AHs. As toxic responses to AHs are believed to be mediated by the aryl hydrocarbon receptor pathway (AHR), several studies compared the structure and expression of AHR pathway molecules between resistant and sensitive fish populations. However, no obvious differences in these molecular parameters were observed between resistant and sensitive populations at the transcriptional level. Further studies at the protein level are recommended to further evaluate the role of the AHR pathway in conferring resistance. Open-ended microarray and proteomic approaches may provide additional resolution in determining the molecular mechanisms of resistance. Also, studies that evaluate the prevalence and ecosystem cost of resistance are needed.

The parasitic sea lamprey Petromyzon marinus occurs throughout North America's Great Lakes, where it has an immense economic impact on commercially and recreationally important fishes. Sea lampreys indisputably invaded Lake Erie and the upper Great Lakes from Lake Ontario in the mid-1900s, but their official status as a nonnative species in Lake Ontario is based on circumstantial evidence and has long been subject to controversy. Presently, sea lampreys are considered by U.S. and Canadian government agencies to be an invasive species within the entire Great Lakes watershed, and millions of dollars are spent annually to suppress them. We sequenced 330 base pairs of the mitochondrial DNA control region of 224 sea lampreys collected from 10 locations (3 within the Lake Ontario drainage, 2 within the Lake Superior drainage, and 5 rivers between Quebec and New York that are tributary to the Atlantic Ocean). Eighteen haplotypes were revealed, of which 17 occurred in specimens from Atlantic coast rivers...

Sea lamprey Fetromyzon marinus from the River Mino and Sella, Spain, showed an almost identical frequency for three observed haplotypes. None of these haplotypes were found among three North American populations. These results indicate an absence of exchange among sea lamprey populations spawning in the west and south-east Atlantic coasts. The similarity between the collections from the two Spanish rivers suggests that homing does not occur in anadromous sea lamprey.

Young-of-the-year (age-0) striped bass Morone saxatilis have been observed during late summer and fall in southern Gulf of St. Lawrence estuaries that may not support striped bass spawning. In this study, we tested the hypothesis that age-0 striped bass in the Richibucto and Kouchibouguac rivers disperse there from the Miramichi River, which is located approximately 35 km north of the Kouchibouguac River and 55 km north of the Richibucto River. Beach seining of the coastline between these three rivers during summer in 1997 and 1998 confirmed the presence of age-0 striped bass in the latter half of August but not before. Age-0 fish distributions over time were consistent with movement from the Miramichi River to the Kouchibouguac and Richibucto estuaries. Microsatellite nuclear DNA and mitochondrial DNA analyses were performed to determine the genetic relatedness among striped bass from these estuaries. Age-0 striped bass from the Shubenacadie River population in the Bay of Fundy, which is known t...

The robust redhorse Moxostoma robustum is a rare catostomid species that was recently “rediscovered” in three Atlantic slope drainages in the southeastern United States, including the Oconee River, Georgia. Adult population size in the Oconee River is declining, and the population may be senescent due to recruitment failure. Evaluation of the environmental factors affecting the success of young life stages requires the ability to distinguish robust redhorse larvae from those of other redhorse species in the Oconee River. The use of morphological approaches, including size at collection date, have proven to be problematic in distinguishing larval robust redhorse from notchlip redhorse M. collapsum from the Oconee River. We developed a mitochondrial DNA (mtDNA) assay to distinguish between reference adults of these two redhorse species from the Oconee, Savannah, and Pee Dee rivers. This mtDNA assay was then applied to unknown larval redhorse collections from the Oconee River. In one collection, dis...

Summary Non-genetic data indicate that Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) are substantially dispersive in marine waters, possibly remaining out of their natal rivers for many years at a time. Gulf sturgeon (A. o. desotoi) only appear to use marine waters during cooler months, summering in rivers. Shortnose sturgeon (A. brevirostrum) are highly residential in rivers, but do sometimes go to sea and move between rivers. We used the polymerase chain reaction (PCR) and direct sequence analysis of a portion of the mitochondrial DNA (mtDNA) control region to examine stock structure, haplotypic diversity, and gene flow ðNfm ) among these taxa, hypothesizing that gene flow would be highest in Atlantic sturgeon. Stock structuring was strong within all three taxa – most river populations supported genetically distinct stocks of sturgeons. Estimates of gene flow among regions were low to moderate in comparison with other anadromous fishes, suggesting that homing fidelity within all three taxa is high. However, average gene flow in Atlantic sturgeon was almost three times higher than in shortnose sturgeon, which somewhat exceeded gene flow values for Gulf sturgeon. Levels and patterns of haplotype diversity differed dramatically between the largely-sympatric Atlantic and shortnose sturgeon. Atlantic sturgeon exhibited a cline in haplotype diversity with monomorphism or very low diversity observed in northern, previously glaciated populations and moderate to high levels of diversity in southern, non-glaciated populations. In contrast, no difference in haplotype diversity and little sharing of haplotypes was observed between northern and southern populations of shortnose sturgeon. We hypothesize that the greater mtDNA diversity in northern populations of shortnose sturgeon resulted from their use of a glacial refugium that was not occupied by Atlantic sturgeon. Gulf sturgeon show much lower gene flow than Atlantic sturgeon. This may be due to their more temporally and geographically constrained marine migrations, which may reduce the opportunities for straying, and a need to return to assured summer thermal refugia. A new finding is the probable existence of a native, genetically-distinct Atlantic sturgeon stock in the James River, which has ramifications for restoration strategies for the species in Chesapeake Bay.