Atlantic Sturgeon Acipenser Oxyrinchus Research Articles

Spawning run estimates and phenology for an extremely small population of Atlantic Sturgeon in the Marshyhope Creek–Nanticoke River system, Chesapeake Bay

AbstractObjectiveOnce thought to be extirpated from the Chesapeake Bay, fall spawning runs of Atlantic Sturgeon Acipenser oxyrinchus have been rediscovered in the Marshyhope Creek (MC)–Nanticoke River (NR) system of Maryland, United States. High recapture rates in past telemetry surveys suggested a small population in the two connected tributaries. This study aims to generate estimates of abundance and understand within system connectivity for spawning runs in 2020 and 2021.MethodsData from mobile side‐scan sonar surveys and detections of acoustically tagged adults on stationary telemetry receivers were analyzed in an integrated model to estimate spawning season abundance and examine run timing and system connectivity for this population. An array of acoustic receivers was deployed throughout the MC–NR system to monitor the movement of tagged fish during the spawning run period from mid‐August to late October. Side‐scan sonar surveys were conducted weekly in September in an area of high spawner aggregation to generate count data on spawning run abundance.ResultIn 2020 and 2021, 32 (95% credible interval [CRI] = 23–47) and 70 (95% CRI = 49–105) Atlantic Sturgeon, respectively, used the MC–NR system. The lower estimate for 2020 coincided with an earlier end to the spawning run related to cooler September temperatures in that year.ConclusionIn both years, high spawning run connectivity between MC and the upper NR was observed. Overall, run estimates supported previous hypotheses that the MC–NR system supports a very small population and that both MC and the upper NR serve as important areas for spawning activity.

A genetic approach to assessing the biodiversity of Atlantic sturgeons <I>Acipenser oxyrinchus</I> and <I>A. sturio</I> (review of modern literature)

The purpose of the review is to summarize modern data on the phylogenetic relationships of two sturgeon species, the North American Atlantic sturgeon Acipenser oxyrinchus and the European Atlantic sturgeon A. sturio, living in the Baltic Sea, due to the complete loss of A. sturio and the presence of a small number of individuals of A. oxyrinchus. Methods used: comparative analysis of modern literature data, a deconstruction method in which studies reflecting the molecular genetic characteristics of species have been carefully selected.The result of the review is structured data on molecular genetic studies of two sturgeon species. Combining research methods conducted with these species in one review.Significance: The results of the generalization are necessary for organizing measures to restore the lost population of sturgeon that lived in the water bodies of the Baltic Sea basin and was lost due to overfishing and changes in the habitat. A systematic approach to the molecular genetic labeling of fish both in the wild and in fish farms will ensure the control of the released juveniles, which will facilitate further research in this field of science.

Seasonal migration cues differ for dual‐spawning Atlantic Sturgeon in the Great Pee Dee River

AbstractObjectiveWe investigated environmental variables associated with spawning migration behavior for a dual‐spawning population of endangered Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus in the Great Pee Dee River, South Carolina.MethodsFrom 2016 to 2021, 147 Atlantic Sturgeon were captured, implanted with acoustic transmitters, and monitored using a stationary array of 40 receivers located every 5–20 km along a 302‐km section of the Great Pee Dee River from the river mouth at Winyah Bay to the first movement barrier at Blewett Falls Dam, North Carolina.ResultWe observed 47 Atlantic Sturgeon attempting 74 spring migrations and 39 Atlantic Sturgeon attempting 76 fall migrations across 4 years of telemetry observations (2018–2021). Mixed‐effects models indicated that discharge interacted with water temperature to affect both migration initiation and upriver movement, and these interactions differed between the spring and fall runs. Spring runs were cued by rising temperatures and high river discharge, whereas fall runs were cued by falling temperatures and low discharge. Within migrations, spring‐run fish migrated further upriver when discharge was falling, and fall‐run fish moved further upriver when discharge was rising. Overall, fall‐run sturgeon migrated significantly further upriver than spring‐run sturgeon.ConclusionDifferences in migratory behavior between the two runs suggest potentially unique adaptations to ambient river conditions during the respective spawning seasons. Identifying the environmental factors that drive—and thereby limit—Atlantic Sturgeon migrations in the Great Pee Dee River informs regional recovery efforts and highlights the importance of studying and managing this species at the population level.

Population and sex-specific survival estimates for Atlantic sturgeon: addressing detection probability and tag loss

Survival estimates of animal populations provide managers with critical information on productivity, population stability, and demography. Telemetry-based survival estimates can be obtained remotely. The Atlantic sturgeon Acipenser oxyrinchus oxyrinchus is a wide-ranging species whose populations overlap along the East Coast of North America, complicating survival estimation. The objective of this study was to estimate apparent annual survival of the York River population using a Cormack-Jolly-Seber model. In this study, 36 males and 24 females were telemetered and monitored between 2013 and 2019. We considered the fit of a variety of models, selecting the best fit using Akaike’s information criterion. The optimal model estimated survival in seasonal increments and detection probability by sex in monthly increments. Five transmitters failed to leave the river and another 3 stopped being detected within 21 mo, but of those, recapturing fish confirmed 2 had been lost and 3 were technological failures (12.8% of 39 recaptured). Apparent adult annual survival was estimated to be 99.2% (95% CL: 97.9-99.7%). Addressing sex-specific detection probability and failed transmitters while including a length covariate for each individual produced higher survival estimates than previously reported studies of Atlantic sturgeon. Four males and one female appear to have died, with the location of last detection for 4 of the suspected mortalities in shipping channels near the mouth of the Chesapeake Bay, suggesting managers should focus on this area of increased risk. Such high survival estimates of the adult stage suggest Atlantic sturgeon survival may be more similar to other long-lived, late-maturing animal species than to most other short-lived fish species.

Stock Composition of the Historical New York Bight Atlantic Sturgeon Fishery Revealed through Microsatellite Analysis of Archived Spines

AbstractA targeted commercial fishery for Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus once operated in the New York Bight, where it was assumed that most harvested Atlantic Sturgeon were natal to the Hudson River population. However, more recent evidence suggests that the fishery may have been targeting a mixed‐stock aggregation, in which case harvested Atlantic Sturgeon could have been comprised of individuals from multiple populations throughout the species’ range. Although there is now a moratorium on Atlantic Sturgeon harvest in the New York Bight, modern molecular approaches provide an opportunity to use archived tissues to perform a retrospective mixed‐stock analysis on the fishery. Genomic DNA extracted from archived fin spines from 80 Atlantic Sturgeon collected nearly 30 years ago suggests that the fishery primarily harvested individuals from the Hudson River population. However, based on individual‐based assignment tests, our results indicate that the fishery also harvested individuals from at least eight other populations located throughout the species’ range. This study highlights how archival hard parts that were previously used for age and growth analyses can be employed for retrospective genetic analyses. Further, because the New York Bight harbors relatively high concentrations of Atlantic Sturgeon, the study shows how localized management decisions can influence Atlantic Sturgeon conservation at rangewide scales. When integrated with more recent knowledge of species ecology, these analyses can be used to evaluate the efficacy of previous management strategies and understand the effects of historical processes on contemporary demography.

Long‐Term Trends in Juvenile Atlantic Sturgeon Abundance May Signal Recovery in the Hudson River, New York, USA

AbstractOverfishing, bycatch, and habitat loss and alteration during the late 19th century to the end of the 20th century caused significant declines in Atlantic Sturgeon Acipenser oxyrinchus stock abundances along the Atlantic coast. To prevent further stock reductions, a coastwide harvest moratorium was implemented in 1998. With fishery‐dependent data unavailable to inform stock management, fishery‐independent surveys contribute vital information for monitoring population trends by providing data for evaluating the effectiveness of the moratorium and for informing recovery planning. In 2004, a standardized monitoring survey was developed to assess trends in the relative abundance of juvenile Atlantic Sturgeon in the Hudson River, New York. The multimesh anchored gill‐net survey randomly sampled locations in soft, deep depositional areas of Haverstraw Bay from late February through early May. Predicted length‐at‐age relationships were used to infer annual age structure and to examine the relationships between age and annual catch rates. Generalized additive regression modeling was used to describe the relationships between the environmental variables and catch rates and to standardize the abundance index to account for variability in environmental conditions over time. Atlantic Sturgeon catch rates generally increased with increasing water temperature and salinity, and the standardized abundance index (accounting for environmental variability) was highly correlated with the nominal abundance index. In the 16 years of annual monitoring, there has been a significant increase in the relative abundance of juvenile Atlantic Sturgeon. The average catch rate in recent years (2012–2019) is more than twice that observed during the first 8 years (2004–2011) of the survey, as the effects of the moratorium are expected to be delayed due to the long maturation period of Atlantic Sturgeon. These trends suggest that juvenile Atlantic Sturgeon in the Hudson River may be recovering in response to the moratorium and demonstrate the need for long‐term fisheries‐independent monitoring to document abundance trends in slow‐maturing, long‐lived species.

Spawning Intervals, Timing, and Riverine Habitat Use of Adult Atlantic Sturgeon in the Hudson River

AbstractThe Hudson River currently supports the largest population of Atlantic Sturgeon Acipenser oxyrinchus in the United States despite currently supporting less than 1% of historic abundance. Federally listed as endangered throughout much of their range, Atlantic Sturgeon are still impacted by multiple threats, resulting in habitat destruction or direct mortality that has inhibited the rebuilding of populations despite more than 20 years without direct fishing pressure. To assist in management and reduction in anthropogenic impacts to adult Atlantic Sturgeon in the Hudson River, we have examined sex‐specific patterns related to spawning. Utilizing hundreds of adult Atlantic Sturgeon telemetered along the Atlantic coast and an extensive passive acoustic array from 2010 to 2016, we were able to estimate arrival, departure, and duration of occupancy for four segments of the Hudson River for male, female, and unknown‐sex individuals. Male Atlantic Sturgeon arrived above river kilometer (RKM; RKM 0 = Battery Park, New York) 100 at an average date of May 27, 12 d prior to females on June 8. While there were only a few significant differences in the timing of departure, the average date from RKM 100 was July 11 for males, June 29 for females, and July 23 for unknown‐sex individuals, as such occupancy was significantly longer for male Atlantic Sturgeon. This study shows that female Atlantic Sturgeon often spawned in consecutive years and had much shorter mean intervals between spawning appearances (females 1.66 years, males 1.28 years) than the historical literature suggests. While the timing of spawning is consistent with the historic record, we provide a timeline with finer resolution and much greater detail for adults in the Hudson River, as well as update the historic estimate of spawning return rates. Conservation measures to reduce direct impacts to spawning habitat and mature Atlantic Sturgeon would likely provide the most benefit if conducted between mid‐May through the end of July.

Raised‐Footrope Gill‐Net Modification Significantly Reduces Subadult Atlantic Sturgeon Bycatch

AbstractBycatch is a major problem in most commercial fisheries around the world and is among the greatest challenges for fisheries managers tasked with conserving, protecting, and sustaining marine resources. Bycatch of protected species is particularly problematic because even small levels of bycatch mortality can hinder conservation efforts. The federally protected Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus is one such example. Unknown numbers of Atlantic Sturgeon are caught as bycatch in commercial gill‐net fisheries along the U.S. Atlantic coast, with discard mortality rates as high as 51%. The Striped Bass Morone saxatilis sink gill‐net fishery in the James River, a tributary to Chesapeake Bay, is the only inshore fishery in Virginia with mesh sizes (13.3–20.3‐cm stretched mesh) that are large enough to have high levels of Atlantic Sturgeon bycatch. This study was conducted during the spring fishery and examined a modified gill‐net design that incorporated a raised footrope at the bottom of the net, creating an approximately 1‐m space between the benthos and the net. The modified net was fished alongside conventional commercial gear to evaluate catch rates of Striped Bass and Atlantic Sturgeon in each gear. Our findings showed that the experimental net significantly reduced bycatch of Atlantic Sturgeon (64.3%) and significantly increased the landings of Striped Bass (45.6%). This gear should be considered as a management option for the spring Striped Bass fishery in Virginia and any fishery in which subadult Atlantic Sturgeon are the primary bycatch. Additional research on seasonal orientation of Atlantic Sturgeon in the water column is needed before adopting the raised‐footrope design in the presence of adults on spawning runs.

Atlantic sturgeon ( Acipenser oxyrinchus oxyrinchus Mitchill, 1815) early life stage consumption evidenced by high‐throughput DNA sequencing

Atlantic sturgeon ( <i>Acipenser oxyrinchus oxyrinchus</i> Mitchill, 1815) early life stage consumption evidenced by high‐throughput DNA sequencing

Seasonal Presence of Atlantic Sturgeon and Sharks at Cape Hatteras, a Large Continental Shelf Constriction to Coastal Migration

AbstractCape Hatteras is a major topographic feature on the continental shelf of the U.S. eastern seaboard that changes the dynamics of nearshore large ocean currents, including the Labrador Current and Gulf Stream. Cape Hatteras constricts shelf habitat and restricts the migratory corridors of highly migratory species through this area. Our objective was to describe the seasonal patterns of presence for three species—the Spiny Dogfish Squalus acanthias, Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus, and Sandbar Shark Carcharhinus plumbeus—and analyze environmental conditions associated with fish presence near this feature. These species are managed under the Magnuson–Stevens Act, and two of them are also listed as species of concern under the Endangered Species Act. Transmitter detections from tagged fish recorded by the Cape Hatteras acoustic array, which was deployed just south of the cape, indicated that these species are present year‐round. The greatest number of detections occurred from November through April. This simple baseline of seasonal presence can provide insights for regional offshore development activities, which have the potential to affect movement patterns of migratory species through the Cape Hatteras constriction. Our results show the value of strategically placed acoustic arrays for observing fish habitat use and provide presence/absence data to enhance our understanding of species ecology and distribution.

Spawning Drivers and Frequency of Endangered Atlantic Sturgeon in the York River System

AbstractDespite over 100 years of commercial exploitation for their eggs, there is limited information about the spawning behavior of Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus. Spawning return intervals for males and females have been estimated in the most general of time spans, and researchers have established only in the last 25 years that Atlantic Sturgeon eggs and larvae are freshwater obligates, dispelling the notion that spawning occurred in estuaries. In this study, capture data from 2013 to 2019 for Atlantic Sturgeon were analyzed to estimate spawning return intervals to the York River system, a tributary to the Chesapeake Bay in Virginia. Then, using the data for female capture, we examined the abiotic influences that appear to drive egg deposition. Both males and females return to spawn at more frequent intervals than has been reported in the literature, with males returning once every 1.13 years and females returning once every 2.19 years. Three females were documented returning to spawn in consecutive years—one of them returning 5 out of 6 years. All of the females that were captured on the spawning grounds were gravid, with eggs at stage 5 or further progressed. In all of the years, 105 fall adult females were caught: 73 were at stage 5, 26 at stage 6, and 6 at stage 7. Of the 26 stage‐6 females, 13 were actively releasing eggs when they were captured. Egg deposition was correlated with photoperiod, water temperature, and a drop in barometric pressure in the 24 h prior to capture. Ten of 13 females that were releasing eggs were caught during day lengths that were within 30 min of the autumn equinox. Females that were releasing eggs were only captured at water temperatures that were between 21.5°C and 25.1°C. This information should provide the foundation of predictive models that allow researchers and managers to understand how this endangered species is likely to respond to climate change.

Use of social network analysis to examine preferential co-occurrences in Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus Mitchill, 1815

BackgroundApplication 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.ResultsIrrespective 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.ConclusionsThe 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.

Using Side‐Scan Sonar and N‐Mixture Modeling to Estimate Atlantic Sturgeon Spawning Migration Abundance

AbstractUnderstanding the relationship between number of spawners and recruitment is essential for managing fish populations. Atlantic Sturgeon Acipenser oxyrinchus (ATS) are endangered anadromous fish inhabiting the rivers, estuaries, and marine environments along the Atlantic coast of North America. Atlantic Sturgeon are periodic life history strategists that exhibit both spring and fall spawning migrations. Traditional capture–mark–recapture techniques can be used to estimate spawning run abundance but are resource intensive and potentially stressful on migrating individuals. Noninvasive methods, such as side‐scan sonar, can be a less stressful alternative to estimating abundance. We sampled the uppermost portion of the Savannah River, USA, over 50 occasions from August to November 2017 using side‐scan sonar. Bayesian N‐mixture modeling was used to estimate spawner abundance and covariate effects based on spatially and temporally replicated count data obtained from sonar recordings. We detected at least one ATS on each sampling occasion and estimated a maximum daily spawner abundance between 35 and 55 individuals (95% credible interval) within the sampled area during the 2017 fall spawning season. Maximum discharge significantly affected ATS detection, and site average maximum depth significantly affected ATS abundance. Our results suggest that side‐scan sonar can be used as an alternative to traditional mark–recapture techniques for spawner abundance estimation. Routine sampling by using our methods will efficiently produce spawning run estimates and provide insight regarding the effects of environmental covariates on spawner abundance seasonally.

Comparing abundance estimates from closed population mark-recapture models of endangered adult Atlantic sturgeon

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 39:63-76 (2019) - DOI: https://doi.org/10.3354/esr00957 Comparing abundance estimates from closed population mark-recapture models of endangered adult Atlantic sturgeon J. E. Kahn1,2,*, C. Hager3, J. C. Watterson4, N. Mathies3, K. J. Hartman2 1National Marine Fisheries Service, Office of Protected Resources, Silver Spring, Maryland 20910, USA 2Division of Forestry and Natural Resources, West Virginia University, Morgantown, West Virginia 26506-6125, USA 3Chesapeake Scientific, Williamsburg, Virginia 23185, USA 4U.S. Department of the Navy, Naval Facilities Engineering Command, Atlantic Norfolk, Virginia 23508, USA *Corresponding author: jason.kahn@noaa.gov ABSTRACT: Atlantic sturgeon Acipenser oxyrinchus oxyrinchus were listed as 5 distinct population segments under the US Endangered Species Act in 2012. At that time, only 2 abundance estimates of the Atlantic sturgeon population were available: one from commercial fisheries landings in the Hudson River ending in 1995 and one from mark-recapture research in the Altamaha River, Georgia, in 2004 and 2005. In 2013, we verified spawning in the York River, Virginia, system and initiated a multiple-year mark-recapture study focusing on spawning-run abundance. We used a Schumacher-Eschmeyer model and Program CAPTURE to produce estimates of annual spawning abundances from 2013 to 2018. The Schumacher-Eschmeyer estimates of spawning-run abundance with 95% confidence intervals from 2013 to 2018 were 75 (31-190), 157 (115-244), 184 (150-238), 222 (137-576), 212 (157-328), and 145 (89-381), respectively. Because Atlantic sturgeon do not spawn every year, the trends in estimates do not suggest a recovering or declining population, but rather variability in proportions of the adult population that return to spawn each year. The estimates produced in Program CAPTURE using M0 (null), Mt (Chao Mt and Darroch), Mh (Chao Mh and Jackknife), and Mth (Chao Mth) models all produced similarly reliable estimates. The models that consider a behavioral response to initial capture (Mb, Mbh, and Mtb) failed to produce reliable estimates for this data, likely because as an endangered species, the dataset for Atlantic sturgeon was sparse. The Jackknife equation (model Mh) was the most precise every year with reliable accuracy and therefore is recommended. KEY WORDS: Anadromous · Conservation · Endangered species · Fish · Mark-recapture · Monitoring · Native fish · Population ecology · Population modeling Full text in pdf format Supplementary material PreviousNextCite this article as: Kahn JE, Hager C, Watterson JC, Mathies N, Hartman KJ (2019) Comparing abundance estimates from closed population mark-recapture models of endangered adult Atlantic sturgeon. Endang Species Res 39:63-76. https://doi.org/10.3354/esr00957 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 39. Online publication date: June 06, 2019 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2019 Inter-Research.

Identifying Environmental Cues for Atlantic Sturgeon and Shortnose Sturgeon Spawning Migrations in the Savannah River

AbstractWe investigated environmental cues for spawning migration behavior of Atlantic Sturgeon Acipenser oxyrinchus and Shortnose Sturgeon A. brevirostrum in the lower Savannah River, South Carolina and Georgia, from January 2013 to May 2018. Sturgeon were implanted with acoustic transmitters and detected on an array of 45 stationary receivers located every 5–10 km between Savannah Harbor and the upstream‐most barrier to movement (301 fluvial kilometers). Throughout the study period, we observed six Atlantic Sturgeon attempting nine fall migrations (n = 918 records), four Atlantic Sturgeon attempting eight spring migrations (n = 257 records), and 15 Shortnose Sturgeon attempting 29 spring migrations (n = 3,542 records). Cues for the initiation of migration and upriver movement were species‐specific. We observed significance in the main effects of water temperature, 3‐d lagged temperature, maximum discharge, and 3‐d lagged discharge, as well as in the interaction effect of 3‐d lagged temperature × 3‐d lagged discharge. Water temperature was the primary predictor of sturgeon migrations, which can be used to determine spawning season, but discharge also played a significant role in predicting upriver movement, particularly when high flows began to diminish. Directed flow regulation (e.g., intermittent flood pulsing) during key temperature thresholds may better facilitate the upriver movement of sturgeons and aid in the conservation of these imperiled species.

Migration patterns and survival of stocked Atlantic sturgeon (Acipenser oxyrinchusMitchill, 1815) in Nemunas Basin, Baltic Sea

The restoration of the Atlantic sturgeon Acipenser oxyrinchus in Lithuania started in 2011. Two rivers (Neris and Šventoji) were chosen for reintroduction in the Nemunas river basin based on historical data and ecological conditions. Since 2011, more than 116 thousand of sturgeon juveniles have been stocked in Lithuania. In order to achieve successful population restoration, it is vital to evaluate the efficiency of performed artificial stocking. Analysis of post-stocking survival, migration patterns, predation pressure, fisheries-related mortality and possible aggregation zones are all important to understand the main threats and prepare possible mitigation measures necessary for population establishment during the initial phase of restoration. Therefore, conventional and radio tagging studies were performed during the initial restoration phase in Lithuania. Atlantic sturgeon downstream migration was divergent in summer and appeared to have no significant associations with fish size, river quality or hydrophysical parameters, but in autumn migration speed and even survival in small rivers seemed to depend on flow velocity and water discharge. The distribution of recaptured tagged juveniles coincided with dominant currents in the Curonian Lagoon and Baltic Sea. Some tagged specimens migrated long distances, with two sturgeons from Lithuania being caught in Estonian and Finnish territorial waters at up to 800 km from their release site. Tag recapture analysis and mortality rate of tagged fish clearly indicate that annual fisheries-related mortality exceeds the required threshold of 5% for population establishment. High survival in rivers indicates that the main threat for a successful sturgeon reintroduction program is commercial fishing in the Curonian Lagoon and Baltic Sea coastal zone.

Fin healing and regeneration in sturgeon.

Pectoral fin healing in fin spines and rays were examined in juvenile Atlantic sturgeon Acipenser oxyrinchus oxyrinchus following three different sampling techniques (n = 8-9 fish per treatment): entire leading fin spine removed, a 1-2 cm portion removed near the point of articulation, or a 1-2 cm portion removed from a secondary fin ray. Also, to determine whether antibiotic treatment influences healing, an additional group of fish (n = 8) was not given an injection of an oxytetracycline (OTC)-based antibiotic following removal of the entire leading fin spine. Following fin sampling, fish from different treatments were mixed equally between three large (4,000 I) recirculating systems and fin-ray healing and mortality were monitored over a 12 month period. To assess healing, blood samples were collected at 4 months to measure immune system responses, radiographs were taken at 4, 8 and 12 months to assess the degree of calcification in regions of damaged fins and fins were analyzed histologically at 12 months. Fish grew from a mean weight of 1.8 to 3.2 kg during the experiment and survival was near 100% in all treatments, with only one fish dying of unknown causes. Leukocyte counts, an indication of health status and survival were similar among treatments and in groups with or without antibiotic injection. Radiographs revealed mineralization took longer in fish with the entire leading fin spine removed and was the slowest near the point of articulation, presumably due to the greater structural support for the pectoral fin at this location. Histological sampling indicated spines and rays had similar healing patterns. Following injury, an orderly matrix of collagen bundles and many evenly spaced scleroblasts were present, transitioning to Sharpey fibres, with concentric layers forming lamellar bone. Healing and mineralization were characterized as periosteal osteogenesis and included embedded osteocytes surrounded by an osteoid seam. Chondroid formation was apparent in a few fractures not associated with treatments. The duration of time for external wound healing and internal mineralization of spines and rays depended on the fin treatment, with the slowest healing observed in fish with the most tissue removed, the entire leading fin spine.

Long-term effect of a tidal, hydroelectric propeller turbine on the populations of three anadromous fish species.

Tidal hydroelectric power has been proposed as one potential solution for sustainable energy sources. The first tidal turbine in North America began continuous operation in the Annapolis River estuary (44 °45'N; 65° 29'W) in June, 1985. The machine is an axial-flow, hydraulic-lift propeller turbine, a type known to cause fish mortality. Anadromous populations of American shad Alosa sapidissima, striped bass Morone saxatilis and Atlantic sturgeon Acipenser oxyrinchus utilize the Annapolis River for spawning and other life history phases. After power generation commenced obvious turbine mortalities of these fishes began appearing downstream of the turbine. Assessments of the A. sapidissima adult spawning runs during 1981-1982 (pre-operation) and 1989-1996 (operational) indicated significant changes in population characteristics after power generation began. Adult length, mass, age and per cent repeat spawners declined and total instantaneous mortality (Z) increased from 0.30 to 0.55. The pre-turbine spawning runs had older fish with numerous adult cohorts whereas by 12 years after operation began runs consisted of younger fish with fewer adult cohorts. During 1972-1987 numerous studies indicated the Annapolis River had an important angling fishery for M. saxatilis, but detailed annual records kept by a fishing contest during 1983-1987 and an elite angler family during the period 1976-2008 demonstrated a rapid decline in the number of fish >4.0 kg after turbine operation began. Pre-turbine catch by the angling family of fish >4.0 kg accounted for 84.1% of total catch, but declined significantly to 39.6% of total catch from 1986-1999, and to none from 2000-2008. The existence of an A. oxyrinchus stock in the Annapolis River was unknown before turbine operation, but during 1985-2017, 21 mortalities were recovered by chance seaward of the turbine. Mechanical strike and cavitation mortalities consisted of juveniles, mature males and gravid and spent females of ages 10 to 53 years found during June to October, the period when this anadromous species returns to its natal river to spawn. The results of the long-term studies at Annapolis indicate managers should realize substantial risks exist for the fish resources of the world's oceans from deployment of instream propeller turbines.

DPS and population origin of subadult Atlantic Sturgeon in the Hudson River

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.

Environmental Drivers of Adult Atlantic Sturgeon Movement and Residency in the Delaware Bay

AbstractAnimals utilize various habitats throughout their life to optimize growth, fitness, and survival. Identifying environmental conditions and locations where animals exhibit different movement behaviors can be used to infer the relative importance of habitat types. In the case of threatened and endangered species, such as the Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus, critical habitat designations are a tool used to promote conservation and recovery. We utilized an extensive passive acoustic telemetry array, observed atmospheric conditions and river flow, modeled seawater conditions, and used generalized additive mixed modeling to determine environmental predictors of Atlantic Sturgeon movement and residency in the Delaware Bay on the U.S. East Coast. Our results suggested that shallower waters, warmer bottom temperatures, and areas toward the eastern portion of the Delaware Bay were predictive of residency, while movement was predicted by increased depth, cooler bottom temperatures, and areas toward the western portion of the bay. Our findings add to a growing body of evidence highlighting habitats at the Delaware Bay mouth, where Atlantic Sturgeon occur at heightened concentrations from late spring through fall. The Delaware River estuary once supported the largest population of Atlantic Sturgeon in North America, but that population is now critically imperiled (or endangered). Atlantic Sturgeon spend the vast majority of their life in marine, polyhaline waters, and without enhanced protection for these habitats, their recovery may never be realized.