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Delineation of essential fish habitat is particularly difficult for migratory fish which utilize large expanses of habitat throughout their life history. This study's main objective was the development and evaluation of habitat assessment tools for the early life stages of American shad (Alosa sapidissima) in two coastal plain rivers. to accomplish this, shad spawning and larval nursery habitats were delineated in the Mattaponi and Pamunkey rivers using presence of eggs and larvae (1997--1999) as evidence of habitat use. A watershed habitat assessment protocol was developed and used to rate habitat based on hydrographic, physical habitat, shoreline and land use parameters. These parameters were evaluated for associations with the presence of shad eggs and larvae to corroborate habitat ratings. Values for parameters used in the ratings were obtained from field assessments, long-term data sets and remote sensing in attempts to combine best-available data. Multivariate statistical analyses indicate the importance of hydrographic parameters (current velocity, dissolved oxygen and depth); physical habitat features (sediment type and deadfall); and forested shoreline/land use features to presence of eggs. Larvae were more dispersed than eggs and distinct habitat associations could not be discerned. Morphological features indicate the presence of three distinct regions along the Mattaponi and Pamunkey river gradients. Presence of eggs is typically associated with upstream and mid-river regions, while larvae were dispersed amongst the three regions. Shad eggs and larvae were more abundant on the Mattaponi River than the Pamunkey River, which is concordant with juvenile abundance. Abiotic factors hypothesized to impact spawning location, larval transport, development rates and predator/prey abundance were also examined. Utilizing the juvenile Alosa index (1991--1999) as an estimate of juvenile shad recruitment, correlation with discharge, precipitation and water temperature (March--June) was examined. Hydrographic conditions during May and June appear to most accurately predict juvenile recruitment patterns in the Mattaponi River, however trends in the Pamunkey River were not as consistent. Ultimately, discharge affects transport of weak-swimming larva to variably favorable nursery habitats. A conceptual hydrodynamic model was developed which explores potential impacts of variable habitat exposures on larvae driven by spawning location, habitat suitability, discharge and hatching rates.

In mammals, the natural resistance-associated macrophage protein 1 gene, Nramp1, plays a major role in resistance to mycobacterial infections. Chesapeake Bay (USA) striped bass, Morone saxatilis, are currently experiencing an epizootic of mycobacteriosis that threatens the health of this ecologically and economically important species. This dissertation characterizes an Nramp gene in this species (MsNramp ) and provide evidence for induction following Mycobacterium exposure. The striped bass MsNramp gene and 554 amino acid sequence contain all the signal features of the Nramp family, including a topology of 12 transmembrane domains (TM), the transport protein specific 'binding-protein-dependent transport system inner membrane component signature,' three N-linked glycosylation sites between TM 7 and TM 8, sites of casein kinase and protein kinase-C phosphorylation in the amino- and carboxy termini and a tyrosine kinase phosphorylation site between TM 6 and TM 7. Phylogenetic analysis most closely groups MsNramp with other teleost Nramps, and exhibits high sequence similarity with mammalian Nramp2. MsNramp expression was present in all tissues assayed by RT-PCR. Within one day of injection with Mycobacterium marinum, MsNramp expression in vivo was highly induced (17-fold) in peritoneal exudate cells (PE) relative to controls. Levels of MsNramp were increased three- and six-fold on days three and 15, respectively. Injection with Mycobacterium shottsii resulted in two-, five-, and three-fold increases in gene expression in PE over the time course. In vitro, PE expressed significantly higher levels of MsNramp at 4 and 24 hours post-treatment with live and heat-killed M. marinum. MsNramp response to LPS was dose-dependent in these cells, with maximum expression at 4 hr and 20 mug/ml LPS. Treatment of PE with LPS caused an increase in intracellular superoxide anion (O2-) levels, whereas treatment with live M. marinum caused a significant depression. Cultured anterior kidney cells responded to LPS with increased O2 - and MsNramp production, but were uninduced or suppressed relative to controls by mycobacteria. This study represents the first report of induction of an Nramp gene by mycobacteria in vivo or in vitro in a poikilothermic vertebrate, and supports reports of teleost Nramp induction by LPS.

The purpose of this study is to obtain information for the formulation of artificial diets for larvae of the American oyster (Crassostrea virginica) and to test procedures related to presenting these diets to the oyster larvae. In order to determine the nutrient components usually provided in larval diets, biochemical analyses of lipids and fatty acids, proteins and amino acids and polysaccharide carbohydrates were performed on five algae species used as a food source for oyster larvae. These algae are Chlorella sp., Pyramimonas virginica, Pseudoisochrysis paradoxa, Pavlova (Monochrysis) lutheri and Isochrysis galbana. The biochemical analyses indicate that the nutritional value of the algal species was not correlated with the total lipid or carbohydrate content, but to the concentration of total protein of the algae. The major fatty acid components of the total lipids of the five species were the C12, C14, C16, and C18 saturated fatty acids and the C16 and C18 mono- and polyunsaturated acids. The total w6 fatty acids were found to be higher in some of the algae. The principal sugar components in the polysaccharide of these five algal species are glucose, mannose, ribose, xylose, rhamnose and fucose. The major constituent was glucose which accounts for 28 to 86% of the total carbohydrate. Mannose was usually the second most abundant carbohydrate component. In addition to the five algae mentioned above, the protein and amino acid composition of four other algal species, Nannochloris oculata, Dunaliella tertiolecta, Phaeodactylum tricornutum and Tetraselmis suecica were also investigated. The major free amino acid components were alanine, arginine, glutamic acid, lysine, proline, serine and taurine. The principal protein amino acids were alanine, aspartic acid, glutamic acid, glycine, leucine, lysine, proline, serine, threonine and valine. Two types of microcapsules, gelatin-acacia and nylon-protein, were tested for acceptability to and digestibility by oyster larvae. Gelatin-acacia and nylon protein capsules were fed to oyster larvae Crassostrea virginica. Larvae were observed to ingest and digest both types of microcapsules. It was found that both types of microcapsules supported growth of larvae. Results also indicated that microcapsule concentration affected growth rate.

Cluster analyses of seasonal (spring and fall) National Marine Fisheries Service Groundfish Survey bottom trawl catches on the Middle Atlantic Bight continental shelf revealed consistent species associations and faunal zones over a nine year period during. Boundaries between faunal zones tended to follow isotherms on the inner portions of the shelf and isobaths along the outer shelf. During the late winter/early spring, four faunal zones were identified: a northern inner and middle shelf zone extending from Cape Cod southward to about Delaware Bay, a northern middle and outer shelf zone offshore of the first zone, a southern middle and outer shelf zone, and a fourth zone on the shelf break and upper slope. The southern inner shelf was a transition zone between the first and third zones. Five species groups were identified: a small cryophilic group restricted to the first zone, a cold-water boreal group found in the first two zones, a ubiquitous boreal/resident group containing the major dominants, a warm-temperate group confined to the warmer southern and outer shelf waters, and a group of slope residents confined to the deepest zone. During the fall, five faunal zones were identified: a southern inner and middle shelf zone, a northern inner shelf zone, a northern mid-shelf zone, an outer shelf zone and a shelf break/upper slope zone. The five species associations recognized were largely analogous to those in the spring, with the following exceptions: the cryophilic group was absent, the ubiquitous group contained mixed boreal and warm-temperate elements, and a second outer shelf group was recognized. The most notable change in the distribution of groups from the spring was a general northward shift in the distributions of the boreal species and a sharply defined inshore movement of the warm temperate group. Analyses of a single summer cruise showed patterns of distribution intermediate to those seen during the spring and fall. Absolute abundances, both of individual species and the total fish community, were highly variable between areas, seasons and years. Species diversity and its components appear to be of little utility in describing the fish communities of the open continental shelves.

A total of 12,323 summer flounder were tagged and released in Chesapeake Bay, the coastal waters off Virginia Beach, and the Eastern Shore during 1987-89. Excluding immediate recaptures, a total of 675 were recaptured for an overall return rate of 5.5%. Returns from the commercial fishery (56.2%) outnumbered those from the recreational fishery (35.7%). The majority of returns (47.1%) came from either Virginia waters or areas to the south, while only 12.8% were from areas to the north of Virginia. offshore returns accounted for 8.5% of the total. Returns with insufficient location data made up the remaining 31.5%. of the returns with sufficient recapture location data, 69% were from Virginia waters or areas to the south. Differences in length at tagging were noted between these groups with smaller fish accounting for a larger proportion of the returns from northern waters. The returns from Virginia waters and areas to the south were more representative of the entire size range of fish tagged. No behavioral differences were noted between tagged and untagged summer flounder held in the laboratory. No tag losses were noted in fish held over the course of one year. Scales were used to age summer flounder and were found to be adequate for ages 0-3, older fish were more difficult to age with scales. Percent agreement between scale and otolith determined ages (n = 170) was 100% for ages 0-5. Length frequencies of summer flounder were used to validate scale determined ages during 1987-89. Prominent modes in length frequencies represented ages 0-2, afterwards, differential growth between the sexes obscured the modes. Marginal increment analysis proved that the marks formed on scales were annular for ages 1-4 and that annulus formation occurred in May-June, at sizes ranging from 179-367 mm TL. Overall mean backcalculated length and the mean observed length in May for age-1 fish were 262 vs 265.4 mm. Mean backcalculated lengths for males were 249, 337, 393, and 455 mm TL for ages 1-4. Mean backcalculated lengths for females were 273, 379, 470, and 550 mm TL for ages 1-4. Backcalculated lengths at ages 1-7 for the pooled sexes were 262, 377, 473, 546, 600, 655, and 696 mm TL. Length-weight relations were calculated by sex for 2,172 fish. Overall sex ratio was 1:1.32, males to females. The sex ratio was approximately 1:1 for length groups up to 360 mm TL. Females outnumbered males at sizes greater than 360 mm TL. Male summer flounder reached 50% maturity at 261-270 mm TL, while females attained 50% maturity at 361-370 mm TL. Overall catch per unit effort decreased from 1.65 fish caught per minute to 0.4 from 1987 to 1989. Instantaneous rates of mortality for summer flounder caught in Chesapeake Bay and coastal waters ranged from 0.964 in 1988, to 1.655 in 1987. Instantaneous rates of mortality for summer flounder caught at Wachapreague ranged from 0.844 in 1989, to 3.608 in 1987.

The most commonly used equation to describe size at age in fishes is the von Bertalanffy equation (VBE), which assumes that growth rate is based on the balance of anabolic and catabolic processes: dW/dt = HW&\sp{lcub}\rm d{rcub}&-kW&\sp{lcub}\rm m{rcub}&. Anabolism, HW&\sp{lcub}\rm d{rcub}&, is considered proportional to gill surface area (A = rW&\sp{lcub}\rm d{rcub}&), and a "generalized" VBE (GVBE) has been previously determined: L&\sb{lcub}\rm t{rcub}& = L&\sb\infty&(1-exp(-KD(t-t&\sb{lcub}\rm O{rcub})))\sp{lcub}\rm 1/D{rcub}&, where D = b-bd and b is from W = qL&\sp{lcub}\rm b{rcub}&. The growth rate may be rewritten in terms of gill area, A, as dW/dt = kA/(A&\sb\infty&/W&\sb\infty\sp{lcub}\rm m{rcub}&)-kW&\sp{lcub}\rm m{rcub}&. Gill areas were examined for sandbar and tiger sharks. Values of the gill area coefficient, d, were fit to a modified Ford-Walford equation (OFW) and the gill area growth equation using length at age data for sandbar, tiger, dusky, blue, white, and shortfin mako sharks to calculate GVBE parameters. The adequacy of the GVBE is dependent on the data set. The OFW produced realistic results for seven data sets, but produced unrealistic L&\sb\infty& estimates for three other data sets. The gill area growth equation produced realistic results for five data sets, but not for two other data sets. A&\sb\infty&/W&\sb\infty& for the lamnid sharks are greater than for the carcharhinids, and within the carcharhinids, A&\sb\infty&/W&\sb\infty& for tiger, dusky and blue sharks are similar, but greater than for sandbar sharks. Growth in individual sandbar sharks was not correlated with individual gill areas. The results support the hypothesis that species- or population-specific dW/dt &\propto& A/W, and that decreasing A/W results in asymptotic growth. However, other factors may obscure the influence of individual variability in gill area on individual variability in growth rates.

Longnose gar (Lepisosteus osseus) inhabit all of the major tributaries of Chesapeake Bay in Virginia, extending from fresh to estuarine waters. Literature concerning longnose gar from tidal environments is limited and this is study concerns important aspects of the life history (e.g., growth, reproduction, dimorphism, movements, and diet). Age, growth, and reproduction are important life history aspects for understanding the biology of fishes and may be affected by the environment in which an individual lives. This study found no differences in the age, growth, and fecundity parameters between longnose gar from tidal portions of Chesapeake Bay tributaries and previous studies in non-tidal environments. Fecundity averaged 30,000 eggs and a von Bertalanffy growth model described growth of longnose gar to be sexually dimorphic, rapid in the first year of life, and leveling off after maturity. Sexual dimorphism has been documented previously in two species of the family Lepisosteidae, L. osseus and L. oculatus. The present study expands upon previous work on this species by examining a broader array of morphometric characters, while removing the bias associated with overall body length. A stepwise discriminant function analyses found that five characters best distinguish the sexes: head width, mid-snout width, anal-fin height, anal-fin width, and prepectoral-fin length. Discriminant function analyses with the five characters and standard length yielded misclassification rates of 8.8% and 6.2% for females and males, respectively. Another goal of this project was to characterize the movements of longnose gar by using both acoustic and conventional tagging methods and by examining historical catch records from a trawl survey. Two individuals moved 69 and 74 km, which is greater than the distance observed in the only other report on long-distance movement by longnose gar individuals. Spawning data were collected from two acoustically tagged longnose gar and spawning residency time was approximately one month. Winter distributions of longnose gar, previously unknown, occurred both inshore and mid-channel and were similar to the summer and fall. Finally, this study characterized the diet of longnose gar inhabiting tidal rivers in Virginia. The top five prey types recovered from stomachs were white perch, menhaden, killifishes (Fundulus spp.), Atlantic croaker, and spot. Marine and anadromous fishes (%W = 59.4%) and resident fishes (%W = 40.6%) were equally important in the diet of longnose gar. The diet varied with the seasonal prey fish assemblages, longnose gar length, and salinity, reinforcing the categorization of the species as an opportunistic predator. The relative abundance, rapid growth, and high fecundity of this apex predator warrant further study and inclusion into ecosystem models.

The structure of surf-zone fish communities at Cassino (western South Atlantic, WSA) and the Chesapeake Bight (western North Atlantic, WNA) is described using historical beach seine data, to examine similarities between geographically isolated fish communities. Numerical classification, ANCOVA, Shanon-Wiener diversity and its components, and species rarefaction are used to describe fish community structure: (a) within habitat (Cassino); (b) within region (Chesapeake Bight); (c) within the western Atlantic (comparison between Cassino and the Chesapeake Bight). The surf-zone fish community at Cassino had a low diversity and was dominated by a few species. Seasonal periods identified by cluster analysis correlated well with seasonal environmental changes. The seasonal occurrence, abundance and diversity of fish species reflected recruitment patterns of juveniles, and seasonal variation in the marine and estuarine circulation patterns. Fish species associations usually fitted into three broad categories: year-round surf-zone residents; (b) spring to fall, estuarine related, pelagic planktivores or shallow water omnivores; (c) summer to fall coastal marine occasionals. Faunal similarity between Cassino and other selected locations of the WSA, decreased towards lower latitudes due to faunal replacements. In the Chesapeake Bight community structure was determined by differences between the two sampled localities. The community at Sandbridge was characterized by estuarine related species associated with the Chesapeake Bay. Sub-tropical coastal marine species at Cape Hatteras indicated influence of Gulf Stream waters. The seasonal species occurrence, abundance and diversity was determined by an enhanced seasonal migration along the coast, juvenile recruitment, and the thermal regime of the Chesapeake Bight. Ubiquitous surf-zone residents were replaced by a wintering group in the colder months. The diversity of estuarine related species at Sandbridge indicated that locally the surf-zone acted as a peripheral habitat for those species. Faunal similarities between the Chesapeake Bight and other WNA localities decreased both northward and southward due to faunal replacements. Similarities between surf-zone fish communities within the western Atlantic (Cassino x Chesapeake Bight) were correlated with the temperature range and habitat structure.