Wetland mitigation has become a 2.4 billion dollar per year industry in the U.S. and in Virginia it leads to the replacement of 77 ha of palustrine forested wetlands (PFWs) per year with mitigation wetlands, including created forested wetlands (CFWs). Mitigation hinges on the idea that compensation wetlands lead to “no net loss of wetland function” when compared to impacted wetlands. We assessed the functions of provision of habitat and biogeochemical functions associated with production of biomass, the retention and removal of nutrients and the accumulation of soil C over 8 years in seven CFWs of approximately 11 and 20 years and compared them to natural reference wetlands (NRWs). CFW plant communities were similar to NRWs in all measured parameters in the herbaceous and shrub/sapling strata and in all strata combined. However, non-native dominance showed a significant positive linear relationship with CFW age. In the tree strata, 11 year old (yo) CFWs had lower richness than NRWs and both age classes of CFWs had lower FQI than NRWs. NRWs held 10 to 20 times more carbon in woody biomass than CFWs. Tree species composition was significantly different between CFWs and NRWs, however NRW trees were similar to CFW saplings. 11 yo CFWs held lower percentages of C, N and P and had higher Db than NRWs in both the 0-10 and 10-20 cm depth. 20 yo CFWs developed similar levels of %C, %P, bulk density (Db), and nutrient ratios in the surface and displayed rapid increases in %C and %N over 8 years. However, CFWs offered 45% lower soil total soil C storage and 50% lower %N. Furthermore, all CFWs stored lower nutrient levels than NRWs in the 10-20 cm soil depth. We found that FQI correlated positively with total C accumulation rates in woody biomass and soil C, indicating that biogeochemical function and the provision of habitat can be complimentary in CFWs. Finally, 11 and 20 yo CFWs adhered to the regulatory performance standards established for Virginia in terms of stems per ha and wetland indicator status, but all wetlands (including NRWs) failed to achieve <5% non-native species cover.

No description available.

The blue crab Callinectes sapidus supports one of the most important fisheries in the Chesapeake Bay and is the leading contributor to blue crab landings in the United States. Assessment and management of blue crab stocks has been hampered by a lack of estimates of natural mortality rates, a key parameter in assessment models. In Chapter 2, we demonstrate that the approach used for estimating natural mortality that had been used in past assessments was flawed, and provide justification for a superior alternative. In Chapter 3, we synthesize our current understanding of natural mortality rates in adult blue crab and provide a suite of estimates for the Chesapeake Bay stock. Our estimates were used in the 2005 assessment for this stock, and the methods and estimates can provide guidance for assessments of the same or other species. In addition to estimates of natural mortality for adult blue crab, the short turnover time in the stock makes it necessary to consider changes in natural mortality rates with size or age. Current assessment models use an annual time step, which smooths over the changes in natural mortality that occur during ontogeny. Some crabs reach an exploitable size within the first year of life, and smaller crabs are expected to have higher natural mortality rates. In addition, natural mortality is known to vary seasonally, being highest in Chesapeake Bay during the summer months when predators are most abundant and crabs are molting frequently. to include size-dependent mortality in more realistic population dynamics models, we estimated mortality rates of juvenile crabs through field experiments (Chapter 4). In 2005 and 2006, we estimated mortality rates of seven cohorts of hatchery-reared juveniles in two tidal marsh creeks along the York River, Virginia during the summer and fall. Juvenile mortality rates were orders of magnitude higher than current estimates of adult mortality rates and were highest in the summer. Our results reinforce concerns about the adequacy of current assessment models and provide estimates of mortality that can be used to guide future work.

No description available.

The results of life history studies involving the sailfish, Istiophorus platypterus, from the Atlantic, Pacific, and Indian oceans were reviewed. Results of studies agree on several aspects of sailfish biology; sailfish exhibit opportunistic feeding behavior, follow the 28??C isotherm, spawn in summer mature at approximately age 3, and are the least migratory of the billfishes. However, results are in conflict concerning sex ratio and whether sailfish are single or multiple spawners. Although many researchers have reported that sailfish are sexually dimorphic, their fragile otoliths make them difficult to age, aging studies have not been validated, and sexual dimorphism has not been adequately separated from differences in age at first maturity. Life history studies are further compromised because identification of early life history stages is difficult and effect of genetically distinct stocks on these studies is unknown. Molecular markers representing a range of genetic resolution were used to investigate the genetic stock structure of the sailfish within and between oceans and to discriminate sailfish from other istiophorid billfishes. to investigate the genetic basis of stock structure, a 1700 by region of mitochondria) DNA which included the control region, was surveyed with five restriction endonucleases and representative individuals were sequenced. In addition, five nuclear microsatellite loci were assayed. Approximately 647 sailfish were collected from throughout the species' range over a six-year period from the Atlantic, Pacific, and Indian Oceans. Both mitochondrial and nuclear markers found that Atlantic, eastern Pacific, and Indo-west Pacific sailfish represent distinct genetic stocks. In addition, mitochondrial data revealed the presence of diverse clades, which were probably formed during Pleistocene glaciation. Independent molecular markers based on mitochondrial and nuclear DNA were developed to provide positive identification of istiophorid and xiphiid billfishes. Both classes of markers are based on amplification of short segments (<1.7 kb) of DNA and subsequent digestion with informative restriction endonucleases. ND4 and MN32-2, the selected markers, allow unambiguous specific identification, although it was not possible to differentiate white marlin and striped marlin. The resulting keys provide two independent means for the forensic identification of fillets and for specific identification of early life history stages.

No description available.

Squaloids (Order Squaliformes) are a highle diverse group of mostly deepwater habitats (> 200 m). Many species are regularly caught in commercial fisheries worldwide but their low productivity and correspondingly low intrinsic rebound potentials make them particularly vulnerable to population depletion and overexploitation. of special concern to fisheries management and conservation efforts are the spiny dogfish Squalus acanthias, the leafscale gulper shark Centrophorus squamosus and the Portuguese dogfish Centroscymnus coelolepis. These taxa have recently been declared overfished in several parts of each species' distribution but management efforts have been made to recover the "stocks" without a good understanding of the species' population structure and the level of connectivity among populations. as such, the goal of this dissertation is to elucidate the intraspecific patterns of population structure of each species, for future inclusion in fisheries management efforts, and to infer the patterns of historical dispersal of the three species of squaloid sharks. to this end, I have developed a suite of highly polymorphic molecular markers (including nuclear microsatellites and nucleotide sequences of mitochondrial DNA gene regions) and have collected tissues samples from throughout each species geographic range. The genetic population structure of S. acanthias was characterized by high genetic divergence across the equatorial Pacific, and by comparatively higher genetic homogeneity among the sample collections from the South Pacific and Atlantic oceans. Nevertheless, small but significant genetic differentiation was detected by both nuclear and mitochondrial markers among spiny dogfish collections from either side of the equatorial Atlantic. Genetic differentiation in the spiny dogfish occurred across low latitude regions characterized by warm-temperate and tropical waters, suggesting that such regions may act as effective barriers to gene flow among populations. Regarding C. coelolepis and C. squamosus, the pattern of genetic population structure uncovered for the eastern Atlantic was similar between species. Within this region, no evidence of genetic differentiation was found among sample collections ranging from off Ireland to South Africa, and including the Azores, consistent with the existence of a single genetic stock for each species within the sampled region. Furthermore, evidence for inter-oceanic dispersal between Atlantic and New Zealand populations was also found for the leafscale gulper. These results strongly suggest that both C. coelolepis and C. squamosus have high dispersal potential and no major barriers to gene flow within the deep eastern Atlantic. Overall, high genetic homogeneity was observed over large geographic areas (i.e. in the order of thousands of miles) in all three target species consistent with long-distance dispersal with gene flow. However, there were differences between the coastal and the deepwater squaloids regarding the regions of genetic discontinuity, which may be associated with adaptations to their respective habitats. In the coastal spiny dogfish, environmental factors such as unsuitable water temperatures appear to exert a strong influence in the species' distribution and in its genetic population structure. In the deepwater squaloids, stable environmental conditions but limited food supply may result in widely distributed populations as a strategy to maximizing resource partitioning while minimizing resource competition among individuals.

No description available.

Panulirus argus Virus 1 (PaV1) is an emerging disease in Caribbean spiny lobster Panulirus argus. It is considered a threat to the lobster industry in the Florida Keys. In order to understand the infection dynamics of the PaV1 virus in the lobster host, a sensitive and specific fluorescence in situ hybridization (FISH) assay was developed for diagnosis of PaV1 in lobsters. The lower limit of detection using the 110-bp DNA probe in a dot-blot hybridization for PaV1 was 10 pg of cloned DNA template and 10 ng of genomic DNA extracted from hemolymph of diseased spiny lobster. The probe specifically hybridized to PaV1-infected cells in all the tissues tested. The probe did not hybridize with host tissues of uninfected spiny lobsters, nor did it cross-react with other virus samples tested. A primary culture of hemocytes was developed for in vitro study of PaV1. The modified Leibovitz L-15 medium supported the best survival of hemocytes in cultures. Hyalinocytes and semigranulocytes maintained higher viability (∼ 80%) after 18 days when cultured separately. Hyalinocytes and semigranulocytes were susceptible to PaV1 in vitro. Cytopathic effects (CPE) were observed as early as 12 h post-inoculation, followed by cell debris and cellular exudates in inoculated cultures. This assay was further developed to assess viral load in hemolymph of diseased lobsters using a 50 tissue culture infectious dose assay (TCID50) based on CPE. The histopathology and hematology of the spiny lobster infected with PaV1 were studied over time courses of experimental infection. The fixed phagocytes in the hepatopancreas were the primary site of PaV1 infection in spiny lobsters. Infection was subsequently observed in the hepatopancreas, gill, heart, hindgut, glial cells around the ventral nerves, as well as in the cuticular epidermis and foregut. as the disease progressed, the hepatopancreas became significantly altered, with hemal sinuses filled with massive amounts of cellular aggregates, including infected circulating hemocytes and a proliferation of infected spongy connective tissues. The virus caused significant decreases in total hemocyte density in later stages of infection and significantly altered several constituents in the hemolymph serum of diseased lobsters, including: glucose, phosphorus, triglycerides, and lipase.

No description available.