The shortnose sturgeon (Acipenser brevirostrum) is an endangered species of fish that inhabits the continental slope of the Atlantic Ocean from New Brunswick, Canada, to Florida.This species has not been documented previously in the freshwater portion of any river of the Chesapeake Bay, except in the Potomac River.On 13 March 2016, a shortnose sturgeon was captured in the freshwater portion of the James River at river kilometer 48.The fish had a fork length of about 75 cm and was likely mature.Genetic analysis confirmed the fish was a shortnose sturgeon and was assigned to the Chesapeake Bay-Delaware population segment.Regardless of whether this shortnose sturgeon was part of a remnant Chesapeake Bay population or whether its capture there is an indicator of an expansion of range from the Delaware River by way of the Chesapeake and Delaware Canal, dedicated research is needed to determine the status of the shortnose sturgeon inhabiting the Chesapeake Bay.
This technical note is the fourth in a series about using native plant communities to achieve engineering and ecological purposes such as shoreline stabilization, structural enhancements, habitat creation, and ecosystem development. In this series, we demonstrate the utility of natural materials (specifically, native vegetation, oyster reefs, and coir logs) in living shoreline projects. Plant species and plant communities play critical roles in wave attenuation and sediment accretion in coastal areas. The application of vegetation in the coastal areas, especially on the East and Gulf Coasts, has focused heavily on the creation of living shorelines—serving both environmental and engineering purposes. This technical note documents the workshop conducted by the US Army Engineering Research and Development Center (ERDC) and hosted by the US Army Corps of Engineers’ (USACE) Philadelphia District (NAP) and Center for the Inland Bays. The goals of this technical note are (1) to demonstrate the application of native plant communities, oyster shells, and coir (coconut) materials and their installation techniques along shorelines to the engineering community; (2) to demonstrate how targeted vegetation establishment can facilitate ecosystem development along shorelines to improve engineering and environmental outcomes; and (3) to provide native vegetation installation techniques for living shorelines projects’ purposes.
Coastal-marine eelgrass habitat is a critical resource within New England and throughout the world. Eelgrass habitat provides functions and services including providing structure, biogeochemical cycling, erosion reduction, habitation provision, and water quality improvement. Declines in eelgrass distribution are often due to anthropogenic processes impacting temperature and water quality. Declines in distribution and abundance highlight the importance of protecting the existing eelgrass, improving environmental conditions allowing for ecosystem restoration, and identifying viable in-kind and out-of-kind compensatory mitigation measures. Considering the limited availability of New England sites for in-kind compensatory mitigation, additional approaches for out-of-kind compensatory mitigation should be considered. These include (1) creation of alternative plant or kelp habitat, (2) using a multi-pronged, multi-habitat and structure approach, (3) contributing to the development of water quality improvement initiatives to encourage current eelgrass bed expansion over time, (4) reduce physical impacts to eelgrass habitat, (5) and identifying locations for future eelgrass habitat suitability based on climate predictions and investing to create future compensatory mitigation habitat in these locations.
Dredging is considered a major threat/impedance to anadromous fish migrating to spawning habitat. Due to the perceived threat caused by dredging, environmental windows that restrict dredge operations are enforced within many rivers along the east coast. However, it is generally unknown how anadromous fish react to encountering an active dredge during spawning migrations. Atlantic sturgeon (ATS) are an endangered, anadromous species along the Atlantic slope of North America. To determine if and how an active dredge may affect ATS spawning migration, a Vemco Positioning System array was deployed around an active hydraulic-cutterhead dredge that adult ATS must traverse to reach spawning habitat in the James River, VA. Telemetry data showed that all ATS that entered the study area survived. ATS that migrated upstream during dredge operations (N = 103) traversed the dredge area and continued upstream to spawning habitat. Many ATS made multiple trips through the study area during dredge operations. There was no noticeable difference in swim behavior regardless of whether the dredge was absent or working within the study area. We suggest that dredging in the lower James River does not create a barrier for adult ATS migrating to spawning habitat or cause adults to significantly modify swim behavior. This is the first study to utilize fine-scale telemetry data to describe how an organism moves in relation to an active dredge. This methodology could be used to describe dredge-sturgeon interactions on different life stages and in other locations and could be expanded to other aquatic organisms of concern.
Populations of sturgeon (Acipenseridae) have experienced global declines, and in some cases extirpation, during the past century. In the current era of climate change and over-harvesting of fishery resources, climate models, based on uncertain boundary conditions, are being used to predict future effects on the Earth's biota. A collection of approximately 400-year-old Atlantic sturgeon spines from a midden in colonial Jamestown, VA, USA, allowed us to compare the age structure and growth rate for a pre-industrial population during a 'mini-ice age' with samples collected from the modern population in the same reach of the James River. Compared with modern fish, the colonial population was characterized by larger and older individuals and exhibited significantly slower growth rates, which were comparable with modern populations at higher latitudes of North America. These results may relate to higher population densities and/or colder water temperatures during colonial times.
Different analytical techniques used on the same data set may lead to different conclusions about the existence and strength of genetic structure. Therefore, reliable interpretation of the results from different methods depends on the efficacy and reliability of different statistical methods. In this paper, we evaluated the performance of multiple analytical methods to detect the presence of a linear barrier dividing populations. We were specifically interested in determining if simulation conditions, such as dispersal ability and genetic equilibrium, affect the power of different analytical methods for detecting barriers. We evaluated two boundary detection methods (Monmonier's algorithm and WOMBLING), two spatial Bayesian clustering methods (TESS and GENELAND), an aspatial clustering approach (STRUCTURE), and two recently developed, non-Bayesian clustering methods [PSMIX and discriminant analysis of principal components (DAPC)]. We found that clustering methods had higher success rates than boundary detection methods and also detected the barrier more quickly. All methods detected the barrier more quickly when dispersal was long distance in comparison to short-distance dispersal scenarios. Bayesian clustering methods performed best overall, both in terms of highest success rates and lowest time to barrier detection, with GENELAND showing the highest power. None of the methods suggested a continuous linear barrier when the data were generated under an isolation-by-distance (IBD) model. However, the clustering methods had higher potential for leading to incorrect barrier inferences under IBD unless strict criteria for successful barrier detection were implemented. Based on our findings and those of previous simulation studies, we discuss the utility of different methods for detecting linear barriers to gene flow.
Abstract Invasive surgical procedures on sturgeon (family Acipenseridae) are sometimes conducted without anesthesia. We examined plasma cortisol concentrations in Atlantic Sturgeon Acipenser oxyrinchus exposed to the anesthetic MS‐222 (tricaine methanesulfonate), electronarcosis, or no anesthetic 1 and 24 h after a small incision mimicking an invasive procedure (tag implantation or laparoscopy). We also determined the feasibility of using electronarcosis in the field and the effect of salinity on electronarcosis. One hour after surgery under electronarcosis or MS‐222 anesthesia, cortisol concentrations did not differ significantly from those in untreated controls but all three were significantly lower than the no‐anesthetic group. There were no significant changes between 1‐ and 24‐h blood cortisol concentrations. We recommend electronarcosis as a method to minimize stress in fish studies involving surgical procedures because it avoids the use of toxic chemicals and because induction and recovery are virtually instantaneous.
