No description available.

This investigation examined the adequacy of the forage base to meet current demand of piscivores in Smith Mountain Lake, Virginia. Surplus production, or the maximum sustainable supply, of alewife (Alosa pseudoharengus) and gizzard shad (Dorosoma cepedianum) were determined using data on the biomass, growth, and mortality of each species. Mean hydroacoustic alewife biomass from 1993-1998 was 37 kg/ha and mean gizzard shad cove rotenone biomass from 1990-1997 was 112 kg/ha. Mean annual alewife surplus production was determined to be 73 kg/ha and mean annual gizzard shad surplus production totaled 146 kg/ha. Bioenergetics modeling and population density estimates were utilized to derive the annual food consumption (realized demand) of the two most popular sport fish in the system, striped bass (Morone saxatilis) and largemouth bass (Micropterus salmoides). The striped bass population consumed 46 kg/ha of alewife and 27 kg/ha of gizzard shad annually. Largemouth bass ate 9 kg/ha of alewife and 15 kg/ha of gizzard shad annually. Annual consumption by ancillary predators was estimated to be 13 kg/ha of alewife and 35 kg/ha of gizzard shad. Prey supply to predators is limited by morphology, behavior, and distribution. The cumulative effect on prey availability of these three factors, in addition to consumption by other predators, was quantified. For largemouth bass, available supply of alewife and gizzard shad exceeded demand by 20% and 53% respectively. For striped bass, available supply of gizzard shad surpassed demand by 30% but available alewife supply was only 4% greater than demand. Annual demand of all predators was 94% of total available clupeid supply. Striped bass stockings were increased by 50% in 1998 and will remain at this level in the near future. A predator-prey simulation model of alewife and striped bass populations was developed to explore the consequences of increased predator demand. This model incorporated dependencies between alewife abundance and mortality and the mortality, abundance, and growth of striped bass. Model output showed that a 50% stocking increase has a near-zero probability of increasing the mean annual number of legal and citation striped bass in Smith Mountain Lake. / Ph. D.

Sunshine and palmetto bass (different crosses of hybrid striped bass) were used to determine immunologic, hematologic and serum chemistry changes under different culture conditions. The kinetics of the humoral immune response was determined for sunshine bass acclimated to 10, 18, 24, 29°C, and to elevated ammonia (0.15 mg/L NH3) and elevated nitrate (200 mg/L). These conditions are frequently encountered in aquaculture situations. Cooler temperatures decreased both the magnitude and onset of the humoral response, being lowest at 10°C, intermediate at 18°C, the highest at 24 and 29°C. Elevated ammonia did not affect the immune response, while elevated nitrate decreased antibody production to the level of the 18°C response. Hematologic reference intervals were determined for sunshine bass in tanks and recirculating systems, and palmetto bass in tanks. Serum chemistry reference intervals were determined for sunshine bass in tanks, recirculating systems and cage systems. Greater differences were observed in reference intervals between the culture systems, than between the two types of hybrid. To determine if environmental factors influenced the differences seen in the reference, sunshine bass were acclimated to 10, 18, 24, 29°C, elevated ammonia (0.15 mg/L NH3) and elevated nitrate (200 mg/L). The hematology and serum chemistry profiles of these fish were compared with the reference intervals for sunshine bass in tanks. Leukocyte, lymphocyte and monocyte counts at 10°C, and glucose and calcium at 10 and 18°C deviated sufficiently to suggest generating separate reference intervals at these temperatures. In the nitrate treated fish, creatinine levels were elevated and chloride levels were lower than controls and outside the reference interval. These two responses were presumed to be pathologic changes associated with elevated nitrate levels due to the large deviation in the analytes and the mortalities seen in the nitrate treated fish. The remaining analytes for fish in the different environments were within or slightly outside the reference intervals. These slight changes were presumed to be due to individual variation as the reference intervals were determined for fish under relatively uniform conditions and may not be sufficiently broad to cover fish from more varied environments. With minor modification, the reference intervals should apply to sunshine bass in most situations. / Ph. D.

TRIAL 1 A preliminary study was conducted to evaluate growth, survival and feed conversion of reciprocal cross hybrid striped bass (<i>Morone chrysops</i> female x <i>Morone saxatilis</i> male) cultured in pilot-scale recirculating aquaculture systems. Hybrid striped bass were stocked in nine 12,500 liter recirculating systems at a mean density of 149 fish/m³. Mean weight at stocking was 40.6 g. Overall survival averaged 72.5%. One system experienced 100% mortality due to the loss of the recirculating pump. Three systems experienced significant mortalities in the middle of the study due to unknown causes. Survival was high, averaging 93.5%, in the remaining systems. Mean daily growth rate of 1 g per day and mean feed conversion of 1.67 compared favorably with that reported in the literature for hybrid striped bass. Slow start-up of new biofilters led to a restricted feeding regime and limited growth. Mean fish weight at harvest averaged 262.1 g with total biomass in the tank averaging 452.57 kg. The recirculating system maintained water quality within ranges adequate for good growth, but the stocking density may have surpassed the systems maximum capacity. TRIAL 2 Results from Trial 1 indicated a need to reduce stocking densities. In Trial 2, three densities of reciprocal cross hybrid striped bass, high (144 fish/m³), medium (72 fish /m³) and low (36 fish/m³) were stocked in eight pilot-scale recirculating systems (12,500 L) and evaluated over 224 days. At stocking, mean weights averaged 34.9, 50.8, and 43.4 g for the high, medium and low treatments, respectively. Fish were hand fed a high protein (44%) floating pellet twice daily. Final weights averaged 412.2 g, 541.1 g, and 676.1 g in the high, medium and low density treatments, respectively. No difference in mean weights were detected between the high and medium densities, but those in the low density were significantly greater (p < 0.05) than the medium and high densities. Total biomass was significantly different (p < 0.05) between treatments at the end of the study and inversely related to mean weight gain, averaging 733.8 kg in the high, 483.3 kg in the medium, and 297.9 kg in the low density treatments. The water quality parameters measured were similar among treatments and adequate for good growth. Feed conversions averaged 1.43 and were not significantly different between treatments. Survival averaged greater than 95% in all treatments. The results of this study demonstrated that hybrid striped bass can grow from fingerling to market size in 224 days in recirculating systems at densities of 36 and 72 fish/m³. If environmental conditions are adequately maintained, it is anticipated that higher densities could reach market size in the same time period. Overall results indicate that hybrid striped bass have good potential for culture in recirculating aquaculture systems. / Master of Science

In this report an investigation on the ovaries of three(3) rock fish was discussed; the sampling of eggs within these ovaries was employed to determine the distribution of large and small eggs in each. From Merriman’s report, a general description of the fish, its habits, etc., was presented, showing significant facts that make the striped bass fisheries one of the great industries of the Atlantic Coast. The rock ovaries inspected came from fish taken in May, November and March. Sampling the ovaries was accomplished in the following manner; the ovary was sliced in six (6) cross-sections, and eight (8) samples were taken from each cross-section in order that a thorough study might be made of the egg distribution from place to place within the ovary. The randomized blocks design was used for the analysis. The large, or mature eggs were separated from the small, or immature eggs in each sample and all were counted under an ocular micrometer. From the egg counts the percent of large eggs present was computed for each sample. An Analysis of Variance was run on the data obtained from the samples of these three ovaries. The Analysis of Variance showed that there was no significant difference in the percent of large eggs present between any section or any position in the ovary. Thus, the large and small eggs together form a homogeneous matrix. The most efficient method of sampling from the ovary of the rock fish, as concluded from the findings in this experiment, is to be obtain samples of eggs at random from the ovary. Each sample should contain more than one hundred fifty (150) ova; the number of samples being determined by precision desired. The number of samples are given in Tables 5a, 5b, and 5c depending upon precision . / M.S.

Natural life history of cephalopods have been puzzling marine biologists for a long time. Fishery scientists also met with great difficulty in managing resources of squids as well as cuttlefishes. The lack of the accurate equation defining growth through time is one of the major reasons. This was due mainly to no stable characteristic for age determinations. It was known that in anatomy, stripe layers of cuttlebone are similar in embryonic development as shells of the bivalve, which has been used for age determinations. This study suggested that by taking the stripe marks on the bottom surface of the cuttlebone as quasi-daily-aging characters, it is possible to define the trend of growth of cuttlefish by (either a von Bertalanffy or Gompertz) growth equation. A semi-automatic computer processing system was designed and organized to measure the stripe area lengths (SAL) and lengths of stripe margin (LSM) for all stripe marks upon individual cuttlebone (analogous to scale reading in fishery research for the same purpose) of ¡]Sepia pharaonic Ehrenberg¡A1831¡^. A total of 21 cuttlebones were measured and the data analyzed. It appeared that the growth of the cuttlefishes are still on the stage of acceleration, and is not suitable to be represented by the VBGF curve traditionally used. Using SAL= and LSM= ' as length indicators respectively, two Gompertz growth equations were respectively estimated as followed. = 30.00*exp[-3.73*exp(-0.012*t)] ' = 23.18*exp[-4.27*exp(-0.015*t)] Two functional linear regression formulas were also prepared as: = -1.2684 + 0.7729 * L ' = -0.7829 + 0.6297 * L The above formulas can be used for the transformation between SAL (or LAM) and body length. The well-known Rosa Lee¡¦s phenomenon was not found either based on the character of SAL or LSM, implying that during the trend of growing, the mortality of Sepia pharaonic were not significantly different among different sizes of organisms. It was expected that with this breakthrough in technique and theory, additional knowledge on the populations biology of cuttlefish can be known in more detail.

The relationship between habitat preferences and rates of dispersal and directional orientation across different vegetations was investigated using captures from an array of drift fences for Pseudacris triseriata , at a breeding pond near Boucherville, Quebec. Growth rates for juveniles were similar across the study area, suggesting that food was not limiting and movement is related to habitat preference. Frog residence time in habitat enclosures, and between fence arrays was significantly longer for frogs in humid prairie vegetation compared to those in shrubby vegetation. The number of frogs caught per metre of fence in humid prairies was also on average higher than either shrubby or arid prairie vegetations. Together both migration rates and captures per metre of fence suggest that the preferred habitat for P. triseriata is humid prairie vegetation (e.g. Phalaris grass). Target-oriented dispersal may explain why similar numbers of P. triseriata were captured in both shrubby and humid prairie vegetation, despite the perceived preference for humid prairies over shrubby vegetation. The continued persistence of this population appears to be based on the recruitment of juveniles from the larval stage, and is also sensitive to the fecundity of the first time breeders.

No description available.

This thesis was partitioned into three studies. In the first study, striped bass, Morone saxatilis, (n = 16) were monitored over a 13 month period to examine the efficacy of ultrasound to determine sex and to monitor sexual maturation. Four observers reviewed all ultrasound images (n = 208) of striped bass and were able to sex male and female striped bass with 99 and 95% accuracy, respectively throughout an annual reproductive cycle. Egg diameter was highly correlated with average (r = 0.89) and maximum (r=0.92) ovarian diameter as measured by ultrasound. Spenniating males exhibited larger maximum testicular diameters (23.5 mm) than non-spermiating males (13.1 mm). Fully mature female and male striped bass exhibited maximum ovarian diameters > 30 mm and testicular diameters > 20 mm as measured by ultrasound. The results of this study indicate that ultrasound is an effective and non-invasive method that aquaculturists can use to quickly scan, sex, and assess the sexual maturation of adult male and female striped bass year-round. In the second study, photothennal manipulation was used to induce spawning out-of season and to increase the frequency of spawning in striped bass, Morone saxatilis. Forty adult striped bass, held in five environmental chambers, were exposed to compressed 6- and 9- month cycles and a 12-month reference cycle. Maximum egg diameters increased with cycle length, averaging 845 urn, 946 urn, and 1,073 um for females held on the 6-, 9-, and 12-month cycles,respectively. Females held on the 6-month cycle had smaller ovarian diameters (19.6 mm) than those held on the 9-month (27.4 mm) and 12-month (24.5 mm) cycles. Ovary diameter was highly correlated with egg diameter (r = 0.91). Spawning success (percent of females spawning) increased with cycle length, averaging 38%, 86%, and 100% in the 6-, 9-, and 12-month cycles, respectively. However, no differences in latent times, fecundity, or fertility were detected between cycles or between tank-spawned and strip-spawned females. Males held on the 6-month cycle had smaller testicular diameters (16.2 mm) than those held on 9-month (23.6 mm) and 12-month (19.2 mm) cycles. Testicular diameter of spenniating males (15.7 mm) was significantly larger than that of non-spenniating males (6.9 rnrn) in all cycles. Mortality increased with cycle length, averaging 28%, 38%, and 88% for fish held on the 6-, 9-, and 12-month cycles, respectively. Maturation and spawning were advanced by five and three months for fish held in the 6- and 9-month cycles, respectively when compared to a natural 12-month reference cycle. Fish held on the 6-month cycle matured twice within a year. However, the relatively low number of spawning females and diminished egg, ovarian, and testicular diameter of fish held on the 6-month cycle suggest that an abbreviated cycle length « 9 months) may inhibit maturation and constrain spawning success. / Master of Science

Doctor of Philosophy / Department of Biology / Samantha Wisely / Emerging infectious diseases play an increasingly critical role in many biological fields, including conservation biology and public health. Many emerging diseases originate in wildlife, most are caused by viruses, and often emergence is due to adaptation to and amplification in a new host, frequently in areas where ecological transformation is occurring. These emergence patterns suggest that the complex interactions among host, virus, and landscape drive disease emergence. Terrestrial rabies in striped skunks (Mephitis mephitis) in the central Great Plains is an excellent model system to investigate the interactions among the components of disease emergence: host ecology, pathogen properties, and landscape features. Striped skunks are not only numerous in the central Great Plains, they are also the reservoir for two genetically distinct rabies strains that co-occur in the region. Additionally, the landscape in the central Great Plains has undergone significant land use change over the last 70 years through increased urbanization and industrial agriculture practices. I used a combination of molecular and spatial techniques to investigate the interactions among host, pathogen, and landscape. Molecular epidemiology results indicated that rabies strains in the central Great Plains exhibit different epidemiological properties, while population genetic analyses indicated that striped skunks in the region are highly admixed and comprise a single population. Spatial analysis revealed that landscape features such as rivers are not a barrier to striped skunk dispersal, but differentially influence the movement of the two rabies strains. Because striped skunks are reservoirs for many diseases other than rabies and are ubiquitous throughout North America, I also examined the historical movements and distribution of striped skunks in North America using a phylogeographic approach. Results revealed that a combination of multiple Pleistocene dispersal events and Holocene admixture are responsible for the contemporary population structure of striped skunks in North America, and allowed me to place my regional-scale striped skunk rabies study into a larger biogeographic context. My results support the use of a holistic approach for studying emerging infectious diseases that includes studies of viral characteristics, host ecology and biogeography, and spatial features.