North American amphibians have recently been impacted by two major emerging pathogens, the fungus Batrachochytrium dendrobatidis (Bd) and iridoviruses in the genus Ranavirus (Rv). Environmental, seasonal and host factors may play important roles in disease dynamics, but few studies incorporate these components into their analyses. Here, we investigated the role of environmental, seasonal, genetic and location effects on driving Bd and Rv infection prevalence and severity in a biodiversity hot spot, the southeastern United States. We used quantitative PCR to characterize Bd and Rv dynamics in natural populations of three amphibian species: Notophthalmus perstriatus, Hyla squirella and Pseudacris ornata and more broadly in multi-species amphibian communities across Florida. We combined pathogen data, genetic and host metrics, and seasonal and environmental variables into statistical models to evaluate how these factors impact infectious disease dynamics. Occurrence, prevalence and intensity of Bd and Rv varied across species, populations, and sites. Pseudacris ornata was found to have high levels of Bd across sites. In Florida, both pathogens were found ubiquitously across sites and seasons and at high levels within three different host families. We conclude that Bd and Rv are more abundant in the southeastern United States than previously thought and that host, seasonal and environmental factors are all important for predicting amphibian pathogen dynamics. Incorporating seasonal, host and environmental information into conservation plans for amphibians is necessary for the development of more effective management strategies to mitigate the impact of emerging infectious diseases.

Age, growth rates, and patterns of movement were studied in the Atlantic stingray, Dasyatis sabina, in the Indian River lagoon system in east central Florida. Age was estimated using the growth rings on the vertebral centrum and tretacycline marking. Tetracycline injections produced clear readable rings in all pups, but failed to be incorporated into the centra of adults. Females possess more centrum rings than males, but annual periodicity could not be verified. Growth rates were determined from aquarium held pups and adults and from tagged and recaptured animals. Males appeared to reach maturity in about two years, females in slightly less than three. Males and females probably reached mean size, 240 and 300 mm, respectively, in six to nine years. Movements of Dasyatis sabina were fairly restricted seasonally as well as annually; the majority (81%) of animals recaptured were taken at the release site. The general age and growth strategies for this species are consistent with those of most other elasmobranchs, characterized by rapid growth the first few years followed by slow adult growth.

The eastern oyster, Crassostrea virginica, once an integral part of the ecology and economy of Chesapeake Bay, has been severely depleted. Factors leading to the decline of the eastern oyster include over-harvesting, environmental degradation and disease pressure caused by the protozoans Haplosporidium nelsoni and Perkinsus marinus, known commonly as MSX and Dermo, respectively. Studies regarding the feasibility of introducing a nonnative oyster to the Bay were initiated, and field-based research on an Asian oyster, Crassostrea ariakensis, suggested that it might be a viable species for introduction. Research surrounding the proposed introduction has focused on recommendations such as those from the International Council for Exploration of the Seas, suggesting that the "ecological, genetic and disease relationships of the species in its natural range and environment" be examined. In order to assess the disease risks associated with C. ariakensis, a parasite survey of oysters collected from China, Japan and Korea was undertaken to examine the pathogens associated with C. ariakensis in its natural range. The protozoan parasites, Perkinsus olseni and a new Perkinsus sp., as well as multiple genetic strains of molluscan herpesvirus, were discovered using molecular diagnostic methods. Molluscan herpesvirus and Perkinsus spp. protozoans are known to cause mortality of many commercially important bivalve species. Characterization of the new Perkinsus sp. included a comprehensive analysis of three DNA loci along with histological examination of the Perkinsus sp. cells in preserved tissue sections. Challenge experiments were undertaken using P. olseni and the new Perkinsus sp. in order to assess the transmission risk of these exotic microbes to the eastern oyster and the hard clam, Mercenaria mercenaria. The laboratory experiments suggest that bivalve shellfish native to Chesapeake Bay may be susceptible to the alien Perkinsus spp. associated with C. ariakensis. In addition, C. ariakensis may acquire moderate to lethal infections of P. marinus under stressful conditions. In light of the proposed introduction of C. ariakensis, it appears that there is a great disease risk associated with this Asian oyster species with the potential to have a negative impact on the naive shellfish populations of Chesapeake Bay.

A size-selectivity curve was constructed to characterize the performance of the New Bedford style Atlantic sea scallop (Placopecten magellanicus) dredge when it is configured to meet the requirements of Amendment #10 to the Sea Scallop Fishery Management Plan. The curve was generated using the SELECT model on catch-at-length data, obtained by simultaneously towing a New Bedford style dredge and a non-selective National Marine Fisheries Service sea scallop survey dredge from commercial scallop vessels. Data were collected during three cruises in the Northwest Atlantic between 2005 and 2006. One cruise was completed in Georges Bank (Groundfish Closed Area II) and two cruises were completed in the mid-Atlantic (both in the Elephant Trunk Closed Area). The resulting selectivity curve for all cruises combined yielded a 50% retention length of 100.1 mm, a selection range of 23.6 mm and a relative efficiency value of 0.77. A length of 100.1 mm corresponds to an age of 4.6 years in Georges Bank and 5.8 years in the mid-Atlantic and a meat-weight of approximately 16 g. This implies that entry into the fishery is being delayed, potentially increasing yield-per-recruit and the population’s total reproductive output. The resultant selectivity curve can assist fisheries managers with stock assessments, mortality calculations and with the interpretation of catch data from government and industry-based surveys. Additionally, the curve can be used to evaluate the effect of future changes to sea scallop dredge design.

The Chesapeake Bay spawning stock of striped bass, Morone saxatilis, is considered one of the largest sources of juvenile production along the Atlantic coast and exhibits a high degree of interannual recruitment variability. Year class strength is judged by near-shore seine surveys that cover major tributaries of Chesapeake Bay and survey results are incorporated into annual stock assessments. In these surveys, the contribution of the Rappahannock River (Virginia) to total production is significant. In this system, abundance of juveniles is highest at a single seine site, suggesting that juvenile production may be related to habitat heterogeneity and food availability. To evaluate this possibility, we describe daily variability in prey consumption, prey composition, and prey selection of juvenile striped bass at the productive site (RK 89) and habitat-specific patterns in feeding along an estuarine gradient that included the productive site. I examined diets of juvenile striped bass collected in five 24-h seine surveys at RK 89 in 1983 and conducted seine hauls at four stations (RK 89, RK 81, RK 71 and RK 60) in 2004. During 24-hr sampling, more fish were caught at 1800 hours and 2100 hours than at other times. In 2004, significantly more fish were caught at RK 89 than at RK 60. Fish were significantly less full at 0300, 0600 and 0000 hours than at all other times. Prey with the highest Index of Relative Importance values were dipteran larvae, calanoid copepods and polychaetes, ranking 1-3 respectively in both years. Peak mean density of Bosmina, other cladocerans, calanoid copepods, and dipteran larvae occurred at RK 89. However, fish were fuller at RK 60 than at RK 89. YOY striped bass showed some indications of selective feeding. As young striped bass grow in the Rappahannock River, they gradually disperse from natal areas into heterogeneous nursery habitats downriver. This ontogeny is reflected in diets as smaller fishes upriver fed on many individuals of smaller plankton prey (especially calanoid copepods) and were less full than cohorts downriver that consumed fewer individuals of larger benthic prey (especially polychaetes).

No description available.

The Longnose Lancetfish, Alepisaurus ferox, is a pelagic marine fish that has a heterodont dentition, including large fangs on both the upper and lower jaws. Their diet is well documented and includes salps, hyperiid amphipods, pelagic polychaete worms, mesopelagic fishes, and cephalopods. However, the function of the heterodont dentition, the structure of the teeth, and replacement mode is largely unknown. We studied a series of A. ferox to describe their dentition and tooth replacement. All teeth are replaced extraosseously. Palatine and dentary fangs develop horizontally in the oral epithelium on the lingual surface of dentigerous bones. Developing fangs rotate into place and attach to the bone through a pedicel that forms at the base of each tooth on the lingual side of the dentigerous bone. We compare extraosseous horizontal tooth replacement and rotation of large fangs in A. ferox to examples of other teleosts rotation of fangs. Atlantic Cutlassfish, Trichiurus lepturus, have large, barbed premaxillary and dentary fangs and sharp, dagger-shaped teeth in their oral jaws. We used dry skeletons, histology, SEM, and micro-CT scanning to study T. lepturus to describe its dentition and tooth replacement. We identified and described three modes of intraosseous tooth replacement in T. lepturus depending on the location of the tooth in the jaw. Such distinct modes of tooth replacement in a teleostean species are unknown. We compared modes of replacement in T. lepturus to 20 species of scombroids to explore the phylogenetic distribution of these three replacement modes. Our study highlights the complexity and variability of intraosseous tooth replacement and that developmentally different tooth replacement processes can yield remarkably similar dentitions. We review literature on the comparative anatomy of Ocean Sunfishes (Molidae) and presents new findings based on our studies. We document similarities and differences among the three living genera, Ranzania, Masturus, and Mola using an organ system approach to examine: general body form and external anatomy; skeleton; integument; brain and sense organs; digestive organs; heart and circulation; respiratory system; excretory system; and endocrine organs. Molids have many anatomical specializations such as the formation of the clavus from dorsal- and anal-fin elements, enlarged gills with unusual skeletal supports, a heart with thick walls and more valves than other teleosts, ontogenetic loss of the swimbladder, enlarged kidneys and a well-developed urinary bladder, reduced otoliths, and a spinal cord contained completely within the braincase. Tagging studies on locomotion and diving behavior demonstrate that molids move efficiently over horizontal and vertical distances in the water column, and this new information helps to interpret the many unusual features of molid anatomy.

The sandbar shark, Carcharhinus plumbeus, is the most abundant large coastal shark in the temperate and tropical waters of the northwest Atlantic Ocean. The Chesapeake Bay, Virginia and adjacent waters serve as a nursery ground for C. plumbeus as well as many other fauna. Characterizing the diet of a higher trophic level predator such as the sandbar shark sheds light on a small portion of the temporally and spatially complex food web in the Bay. This study describes the diet of the sandbar shark, highlighting differences in diet within various portions of the nursery area, as well as ontogenetic changes in diet. Stomach samples were obtained in 2001 and 2002 from 232 sharks caught in gillnets or by longline gear. Historical data from the Virginia Institute of Marine Science (VIMS) Shark Ecology program were also analyzed. Ontogenetic changes in diet were evident, with crustacean prey decreasing in importance and frequency with increasing shark size, and elasmobranch prey importance and frequency increasing with increasing shark size. While previous research in Chincoteague Bay, VA showed the blue crab, Callinectes sapidus, as the dominant crustacean in sandbar shark diet, the mantis shrimp, Squilla empusa, dominated the crustacean portion of the diet in this study. Differences in diet were mainly attributable to location of shark capture. Small juveniles (< 80 cm precaudal length) in the lower Chesapeake Bay ate significantly more fishes, whereas Eastern Shore juveniles ate more crustaceans. The type of crustacean consumed varied within areas of the Eastern Shore, with more portunid crabs consumed in waters near Wachapreague and more mantis shrimp consumed near Sand Shoal Inlet. This study was not able to detect any change in diet over time due to insufficient sample sizes and the effect of location.

The lower Chesapeake Bay and adjacent coastal waters serve as the primary summer nursery areas for juvenile sandbar sharks (Carcharhinus plumbeus) in the Northwest Atlantic Ocean. The large population of juvenile sandbar sharks in this ecosystem benefits from increased food availability that fuels rapid growth and from limited exposure to large shark predators. Juvenile growth and survival is the most critical life history stage for sandbar sharks, and juvenile nursery grounds will continue to play an important role in the slow recovery of this stock from severe population declines due to overfishing. The goal of this study was to assess the possible impacts of juvenile sandbar sharks as apex predators on the lower Chesapeake Bay ecosystem and to evaluate the energetic benefits of using this nursery. The bioenergetics model was used as a tool to predict energy consumption rates of individual sandbar sharks based on their energetic demands: metabolism, growth, and loss of waste. Metabolic rate is the largest and most variable component of the energy budget, particularly for species such as the sandbar shark that must swim continuously to ventilate their gills. The standard (basal) and routine metabolic rates of juvenile sandbar sharks were measured in two laboratory respirometry systems, using oxygen consumption rate as a proxy for metabolic rate. These data span the entire range of body sizes and water temperatures characteristic of the Chesapeake Bay population. Standard metabolic rates of sandbar sharks were similar to values obtained for related shark species by extrapolation of power-performance curves. The effects of body size and temperature on standard metabolic rate were similar to previous results for elasmobranchs and teleost fishes. In fifteen sharks, routine metabolic rate while swimming averaged 1.8 times the standard metabolic rate when the sharks were immobilized. Data obtained from the literature support the theory that limited gill surface areas and narrow metabolic scopes of many elasmobranchs help to explain their slow growth rates, since growth has the lowest rank of the multiple metabolic demands placed on the oxygen delivery system. These new metabolic rate data were then combined with other species-specific data to construct a bioenergetics model for juvenile sandbar sharks for the time they spend in Chesapeake Bay each summer. This model predicted higher daily rations than previous estimates for this species that were based on simple bioenergetics models or stomach contents and gastric evacuation rate models. However, the predicted rations agree with reconstructed meal sizes of juvenile sandbar sharks and are comparable to those of ecologically similar shark species. When extrapolated from individuals to the population level, the model predicted a negligible effect of predation by juvenile sandbar sharks on the lower Chesapeake Bay ecosystem; the consumption rate of juvenile sandbar sharks pales in comparison to other carnivorous fishes and to humans, the true apex predators in the system.

Only a miniscule fraction of the world’s largest volume of living space, the ocean’s mid-water biome, has ever been sampled. As part of the International Census of Marine Life field project Mid-Atlantic Ridge Ecosystems (MAR-ECO), a discrete-depth trawling survey was conducted in 2009 aboard the NOAA ship Henry B. Bigelow to examine the pelagic faunal assemblage structure and distribution over the Charlie-Gibbs Fracture Zone (CGFZ) of the northern Mid-Atlantic Ridge. This is the first MAR-ECO project aimed specifically at describing diel vertical migration as a distributional phenomenon. Discrete-depth sampling from 0-3000 m was conducted during both day and night in similar locations using a Norwegian “Krill” trawl with five codends that were opened and closed via a pre-programmed timer. Seventy-five species of fish were collected, with a maximum diversity and biomass observed between depths of 700-1900 m. An incremental gradient in sea surface temperature and underlying watermasses, from northwest of the CGFZ zone to the southeast, was mirrored by a similar gradient in ichthyofaunal diversity. Using multivariate analyses, eight deep-pelagic fish assemblages were identified, with depth as the overwhelming discriminatory variable. Strong diel vertical migration (DVM) of the mesopelagic fauna was a prevalent feature of the study area, though the numerically dominant fish, Cyclothone microdon (Gonostomatidae), exhibited a broad (0-3000 m) vertical distribution and did not appear to migrate on a diel basis. In all, 3 patterns of vertical distribution were observed in the study area: a) DVM of mesopelagic, and possibly bathypelagic, taxa; b) broad vertical distribution spanning meso- and bathypelagic depths; and c) discrete vertical distribution patterns. Overall species composition and rank order of abundance of fish species agreed with two previous expeditions to the CGFZ (1982-83 and 2004), suggesting some stability in the ichthyofaunal composition of the study area, at least in the summer. Frequent captures of putative bathypelagic fishes, shrimps, and squid in the epipelagic zone (0-200 m) were confirmed. The results of this expedition reveal distributional patterns unlike those previously reported for open ocean ecosystems, with the implication of increased transfer efficiency of surface production to great depths in the mid-North Atlantic.