Baseline health and nutritional parameters of wild Sand Tigers Carcharias taurus sampled in Delaware Bay

Species-specific hematological reference values are essential for diagnosis and treatment of disease and maintaining overall health of animals. This information is lacking for many species of elasmobranchs maintained in zoos and aquaria, thus reducing the effectiveness of care for these animals. Descriptive statistics and reference intervals were calculated for hematocrit and complete blood cell counts, biochemistry and protein electrophoresis parameters, trace minerals, vitamins, heavy metals, reproductive hormones, and fatty acids in the blood of 153 wild Sand Tigers Carcharias taurus of both sexes and a range of sizes caught in Delaware Bay (Delaware, USA). Mean hematocrit, total white blood cell counts, lymphocyte differentials, glucose, phosphorous, amylase, and aspartate aminotransferase levels were significantly higher in juveniles than in adults. Levels of estradiol, progesterone, testosterone and differences in selenium, and the polyunsaturated fatty acid 20:5n3 (eicosapentaeonic acid) between males and females suggest that they are important parameters for improving Sand Tiger breeding success in managed care. Finally, blood metal levels for arsenic, cadmium, lead, and mercury suggest low levels of contaminant exposure of Sand Tigers in Delaware Bay during their summer residence in the bay. The results of this study provide baseline health parameters for wild Sand Tigers that will aid in effective maintenance of aquarium animals and that contributes to a greater understanding of the biology of these sharks and efforts to accomplish sustainable management of their populations

Effective Population Size and Genetic Diversity of a Species of Concern, the Sand Tiger Shark (Carcharias taurus) in Delaware Bay, USA

Genetic assessments can provide a conservation and management relevant perspective on the status of imperiled species including sand tigers, (Carcharias taurus). Sand tigers within the western North Atlantic were listed as a Species of Concern and thus prohibited from recreational and commercial fisheries in 1997 by the National Marine Fisheries Service. A previous global population study of sand tigers revealed the genetic isolation of individuals inhabiting the western North Atlantic from the remainder of this species\u27 distribution. Here, we assess the genetic status, including effective population size and genetic diversity of sand tigers from an area of known high abundance: Delaware Bay (n=557). Eleven species-specific microsatellite markers were used to analyze temporal variation in effective population size and genetic diversity of sand tigers collected from 2007-2012. Total length was used to back-calculate age estimates for each sex using data from a previous age and growth study on sand tigers within this region. Individual sharks of similar estimated age were grouped together to form year classes. Preliminary results indicate little genetic differentiation among year classes with respect to genetic diversity and effective population size, suggesting relatively stable, recent temporal population dynamics for Delaware Bay sand tigers. Estimates of genetic diversity (allelic richness) of sand tigers captured within Delaware Bay were greater than the previous survey within the western North Atlantic, suggestive of recovery in this previously exploited population

Shifting Distributions of Adult Atlantic Sturgeon Amidst Post-Industrialization and Future Impacts in the Delaware River: a Maximum Entropy Approach

<div><p>Atlantic sturgeon (<i>Acipenser oxyrinchus oxyrinchus</i>) experienced severe declines due to habitat destruction and overfishing beginning in the late 19^th century. Subsequent to the boom and bust period of exploitation, there has been minimal fishing pressure and improving habitats. However, lack of recovery led to the 2012 listing of Atlantic sturgeon under the Endangered Species Act. Although habitats may be improving, the availability of high quality spawning habitat, essential for the survival and development of eggs and larvae may still be a limiting factor in the recovery of Atlantic sturgeon. To estimate adult Atlantic sturgeon spatial distributions during riverine occupancy in the Delaware River, we utilized a maximum entropy (MaxEnt) approach along with passive biotelemetry during the likely spawning season. We found that substrate composition and distance from the salt front significantly influenced the locations of adult Atlantic sturgeon in the Delaware River. To broaden the scope of this study we projected our model onto four scenarios depicting varying locations of the salt front in the Delaware River: the contemporary location of the salt front during the likely spawning season, the location of the salt front during the historic fishery in the late 19^th century, an estimated shift in the salt front by the year 2100 due to climate change, and an extreme drought scenario, similar to that which occurred in the 1960’s. The movement of the salt front upstream as a result of dredging and climate change likely eliminated historic spawning habitats and currently threatens areas where Atlantic sturgeon spawning may be taking place. Identifying where suitable spawning substrate and water chemistry intersect with the likely occurrence of adult Atlantic sturgeon in the Delaware River highlights essential spawning habitats, enhancing recovery prospects for this imperiled species. </p> </div

Migratory patterns and habitat use of the sand tiger shark (Carcharias taurus) in the western North Atlantic

Globally, population declines for the sand tiger shark (Carcharias taurus) have resulted in calls for informed management of populations, including in the western North Atlantic, where they have been listed as a Species of Concern by NOAA Fisheries. However, information on movements and habitat use, critical for informed management of this sand tiger population, is limited. We investigated horizontal and vertical movements of sand tigers along the US east coast using pop-up archival satellite transmitters, supplemented by acoustic telemetry. Thirteen sand tiger sharks were tagged with satellite and acoustic transmitters in Delaware Bay in late August and early September 2008. Ten of these provided satellite data for horizontal tracks using a Kalman filter. Males left Delaware Bay in autumn and moved south along the continental shelf until reaching waters off North Carolina. Females moved east to waters near the edge of the continental slope. Average depth of males was positively correlated with shark size. All individuals spent at least 95% of their time in waters of 17-23;C. Sand tiger sharks appear most susceptible to fisheries in November and December. Slight expansion of the boundaries and timing of an existing shark-directed bottom longline area closure would likely reduce by-catch of sand tiger sharks and enhance recovery of the stock

Coastal Movements of Sand Tiger Sharks (Carcharias taurus) in the Northwest Atlantic as Determined by Acoustic and Satellite Telemetry

Prior to a recent harvest moratorium, sand tiger sharks (Carcharias taurus) were the focus of both directed and non-directed fisheries in the northwest Atlantic. Sand tigers occupy a high public profile due to their size and relative ease of public display. In contrast with many other large coastal sharks, limited information is available on the coastal movements of sand tigers including locations of overwintering areas. In 2008 we outfitted 13 sand tigers (1.4-3.3m FL) with acoustic (VEMCO Ltd. V-16-6H) and satellite (Microwave Telemetry Inc.) transmitters in Delaware Bay. Twelve of the thirteen acoustic transmitters were detected a total of 8,030 times prior to departing Delaware waters in September and October. Similarly, twelve of the satellite transmitters were detected within scheduled pop-off times (4-6 months post-deployment). Most sand tigers made relatively direct movements to overwintering areas in the Hatteras Bight Region, arriving within weeks of departing Delaware waters. An additional male sand tiger (1.09m FL) outfitted with an acoustic transmitter was detected off Cape Canaveral, FL in January-February, 2009 after departing Delaware Bay in September. Female sand tigers occupied significantly (p \u3c.0001) warmer waters compared to males although occupied depths did not vary significantly (p=.1054). Although perceived as a relatively sluggish species, telemetered sand tigers were documented making rapid movements in the water column from surface waters to depths of 188m. Our results underscore the need for coast-wide approaches to recover sand tigers as this charismatic shark is particularly vulnerable to anthropogenic impacts

Implantation and Recovery of Long-Term Archival Transceivers in a Migratory Shark with High Site Fidelity

Publisher's PDF.We developed a long-term tagging method that can be used to understand species assemblages and social groupings associated with large marine fishes such as the Sand Tiger shark Carcharias taurus.We deployed internally implanted archival VEMCO Mobile Transceivers (VMTs; VEMCO Ltd. Nova Scotia, Canada) in 20 adult Sand Tigers, of which two tags were successfully recovered (10%). The recovered VMTs recorded 29,646 and 44,210 detections of telemetered animals respectively. To our knowledge, this is the first study to demonstrate a method for long-term (~ 1 year) archival acoustic transceiver tag implantation, retention, and recovery in a highly migratory marine fish. Results show low presumed mortality (n = 1, 5%), high VMT retention, and that non-lethal recovery after almost a year at liberty can be achieved for archival acoustic transceivers. This method can be applied to study the social interactions and behavioral ecology of large marine fishes.University of Delaware. College of Earth, Ocean, and Environment

Acoustic receiver locations and 1 km detection radius overlain on the sediment composition map of the Delaware River (adapted from Sommerfield and Madson 2003), location of the salt front shown given four different scenarios, urban areas indicated through dark shading.

<p>Acoustic receiver locations and 1 km detection radius overlain on the sediment composition map of the Delaware River (adapted from Sommerfield and Madson 2003), location of the salt front shown given four different scenarios, urban areas indicated through dark shading.</p

Density of observations by distance from salt front for telemetered adult Atlantic sturgeon in the Delaware River during the likely period of spawning from 2009-2012.

<p>Density of observations by distance from salt front for telemetered adult Atlantic sturgeon in the Delaware River during the likely period of spawning from 2009-2012.</p

Differential migration in Chesapeake Bay striped bass.

Differential migration-increased migration propensity with increasing individual size-is common in migratory species. Like other forms of partial migration, it provides spatial buffering against regional differences in habitat quality and sources of mortality. We investigated differential migration and its consequences to survival and reproductive patterns in striped bass, a species with well-known plasticity in migration behaviors. A size-stratified sample of Potomac River (Chesapeake Bay) Morone saxatilis striped bass was implanted with acoustic transmitters and their subsequent coastal shelf migrations recorded over a 4-yr period by telemetry receivers throughout the Mid-Atlantic Bight and Southern New England. A generalized linear mixed model predicted that ≥ 50% of both males and females depart the Chesapeake Bay at large sizes >80 cm total length. Egressing striped bass exited through both the Chesapeake Bay mouth and Delaware Bay (via the Chesapeake and Delaware Canal), favoring the former. All large fish migrated to Massachusetts shelf waters and in subsequent years repeatedly returned to regions within Massachusetts and Cape Cod Bays. Within this dominant behavior, minority behaviors included straying, skipped spawning, and residency by large individuals (those expected to migrate). Analysis of the last day of transmission indicated that small resident striped bass experienced nearly 2-fold higher loss rates (70% yr-1) than coastal shelf emigrants (37% yr-1). The study confirmed expectations for a threshold size at emigration and different mortality levels between Chesapeake Bay (resident) and ocean (migratory) population contingents; and supported the central premise of the current assessment and management framework of a two-contingent population: smaller Chesapeake Bay residents and a larger ocean contingent. An improved understanding of differential migration thus affords an opportunity to specify stock assessments according to different population sub-components, and tailor reference points and control rules between regions and fishing stakeholder groups