VTechWorks Repository :: Browsing by Author "Helfrich, Louis A."

Browsing by Author "Helfrich, Louis A."

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Clearing Muddy Pond Waters
Helfrich, Louis A.; Newcomb, Tammy J. (Virginia Cooperative Extension, 2009-05-01)
Explains the influences muddy pond waters can have on aquatic life and provides protocols and treatments to use in order to keep pond water clear.
Commercial Frog Farming
Helfrich, Louis A.; Neves, Richard J.; Parkhurst, James A. (Virginia Cooperative Extension, 2009-05-01)
Explains the reasons that raising and selling frogs on a commercial basis has not proven to be successful economically in Virginia or elsewhere in the United States and provides opinions on the future of the practice.
Common water plants of Virginia
Helfrich, Louis A.; Pardue, Garland B.; Weigmann, Diana L. (Virginia Cooperative Extension Service, 1981-10)
Identification guide to Virginia's aquatic plants.
Comparison of Water Quality, Rainbow Trout Production, and Economics in Oxygenated and Aerated Raceways
Clark, Michael Louis (Virginia Tech, 2003-12-05)
The effects of oxygenation and aeration on water quality, rainbow trout (Oncorhynchus mykiss) production, and economics were compared at the Wytheville State Fish Hatchery (WSFH) for 270 days. Mean dissolved oxygen (DO) concentrations and delta DO were significantly higher (P < 0.001) in the oxygenated raceways (9.5 and 2.75 mg/L, respectively) compared to aerated raceways (7.4 and 0.57 mg/L). Total settleable solids loads were significantly greater (P < 0.001) in aerated raceways (10.3 g/L/day) than in oxygenated raceways (8.8 g/L/day). Dissolved nitrogen (%), total gas pressure, and other water quality parameters (CO2, nitrite nitrogen, alkalinity, pH, and TAN) did not differ significantly between the treatments (P > 0.05). Raceway trout production (kg/day), trout growth rates (grams), feed conversion rate (FCR), and fish survival were not significantly different between treatments (P > 0.05). Blood hematocrit (Hct) and percent visceral mass were significantly elevated (P < 0.001) in oxygenated raceways compared to aerated raceways at 46 and 14.4% and 44 and 13%, respectively. Carrying capacity estimates derived from fish loading trials were significantly different (P < 0.001) at 3,355 and 2,217 kg/raceway in oxygenated and aerated raceways, respectively. Estimates of carrying capacity calculated using a fish loading (Ld) equation were also significantly different (P < 0.001) at 1,530 and 990 kg for oxygenated and aerated raceways, respectively. Oxygen injection increased the cost of production by $0.20/kg, however, net present value analysis (NPV) of oxygenated and aerated raceways over 5 years at a 10% discount rate yielded estimates of $50,666.51 and $32,742.15, respectively. Oxygen injection is an effective means of increasing DO concentrations, reducing effluent solids loading, and increasing raceway carrying capacity.
Continuing educational needs of state agency fish and wildlife biologists
Murphy, William F. (Virginia Tech, 1994)
Fishery and wildlife biologists employed by state fish and wildlife agencies were surveyed to determine their continuing education needs related to specific job tasks. In addition, proficiency levels required for job tasks were rated. An organizational analysis was also conducted to ascertain agency climate for support of continuing education programs. Forty-seven state fish and wildlife agencies responded to the organizational analysis. Agencies valued their employees and understand the benefits of continuing education, but did not allocate many resources to support programs. A positive climate does not presently exist for the development and implementation of continuing education programs. Continuing education was not an important part of state fish and game agencies’ organizational culture. Differences in continuing education needs of fishery and wildlife biologist have little correlation to undergraduate/graduate curricula, highest degrees attained, or length in the profession. Biologists’ greatest needs for continuing education related to technical tasks in research/data collection and analysis, and specifically computer and software usage. Other continuing education needs were related to population and habitat tasks. Biologists identified low proficiency levels needed for modeling and genetic tasks, but indicated a high need for continuing education. Continuing education needs for non-technical tasks related to communication, interpersonal relations, management and leadership skills were rated significantly higher by agency administration than fishery and wildlife biologists. Additional data were provided on proficiency levels identified for job tasks. Recommendations are made to state fish and wildlife agencies, providers of continuing education programming, and university faculty.
Control Methods For Aquatic Plants in Ponds and Lakes
Helfrich, Louis A.; Neves, Richard J.; Libey, George S.; Newcomb, Tammy J. (Virginia Cooperative Extension, 2009-05-01)
Explains the negative impacts that can occur from dense growths (over 25% of the surface area) of aquatic plants in ponds and lakes and provides practical methods of management of these plants.
Control methods for aquatic plants in ponds and lakes
Helfrich, Louis A. (Virginia Cooperative Extension, 2000)
The Control of Burrowing Crayfish in Ponds
Helfrich, Louis A.; Parkhurst, James A.; Neves, Richard J. (Virginia Cooperative Extension, 2009-05-01)
Provides basic information of the crayfish including their ecological and economic importance, their burrows, how they breed, and how they can be controlled in pond dams, irrigation canals, and drainage ditches.
Controlled cultivation techniques for the recovery of threatened fishes in Virginia
Stoeckel, Joseph Norman (Virginia Tech, 1993)
The goal of this research was to develop captive propagation methods for the Federally threatened spotfin chub, Cyprinella monacha, and yellowfin madtom, Noturus flavipinnis, by using closely related, but unthreatened species, to evaluate potential techniques. The surrogate species used were the whitetail shiner, Cyprinella galactura, and the margined madtom, Noturus insignis. I investigated methods to promote gonadal maturation, induce spawning, and rear larvae of these fishes. Captive whitetail shiners developed mature gonads under a variety of temperature and photoperiod conditions. Spawning condition was maintained for over two years when they were held at constant warm temperature (≈ 24 C) and long photoperiod (16 h light). Whitetail shiners did not readily spawn in aquaria, but were induced to spawn by hormonal injection with human chorionic gonadotropin (hCG) and carp pituitary extract (CPE) at mean dosages of 1688 I.U./kg and 20 mg/kg, respectively, or with luteinizing hormone releasing hormone analogue (LHRHa) and domperidone at mean dosages of 363 µg/kg and 36 mg/kg, respectively. Most females spawned within 30 h of the first injection. Stripped ova were effectively wet-spawned, and larvae hatched in 8 d at 25 C. I obtained a mean hatch rate of 55 %, but lack of swimbladder inflation resulted in very poor survival of several batches of eggs. Larvae began feeding within 2 d of hatching, and survival rates of 50 to 90 % after 16 d were obtained when larvae were fed twice daily on a diet of brine shrimp nauplii at a rate of ≈ 10/L/d, and a commercially prepared larval fish diet at a rate of ≈ 14 mg/L/d. Changing photoperiod, but not temperature, was required to induce oocyte maturation in most captive female margined madtoms. Sperm production in mature male madtoms was enigmatic; motile sperm were observed only once. Plasma testosterone concentrations in males peaked just prior to the spawning season at 6.5 ng/mL, but levels were not correlated with male gonadosomatic values. Plasma 17β-estradiol levels in females peaked just prior to the spawning season at 15 ng/mL, and were correlated with gonadosomatic values. Captive margined madtoms did not tank spawn unless they were hormonally injected with hCG and CPE at mean dosages of 5256 I.U./kg and 58 mg/kg, respectively, or with LHRHa and domperidone at mean dosages of 554 µg/kg and 55 mg/kg, respectively. Most females ovulated within 78 h of the first injection. Inclusion of more than one breeding pair per tank inhibited tank spawning. Embryos did not develop in 55 % of tank-spawned ova, or from any strip-spawned ova. Parents consumed spawned egg masses if they remained with the nest. Hatch rates > 65 % were obtained by suspending egg masses in a large-mesh basket over turbulent aeration at 28 to 30 C. Larvae hatched in 7 d at 28 C. Survival rates > 50 % after 15 d were obtained when larvae were fed salmon starter twice daily at a rate of 20 mg/L/d, and tanks were thoroughly cleaned daily.
Dietary Selenium in Cultured Hybrid Striped Bass
Cotter, Paul (Virginia Tech, 2006-04-17)
As aquaculture continues to contribute high quality protein to a greater proportion of the worlds growing population, fish producers have been pressured to increase overall production. However, associated with elevated production is greater stress due to crowding, reduced water quality, and other factors. These stressors impact the health and welfare of the farmed animal which has become of increasing concern to a more environmentally aware and health conscious consumer. New strategies must therefore be developed and adopted by the aquaculture industry to counteract negative consumer perceptions of industrial fish production while also stabilizing the industry. Better nutrition may enhance disease resistance of farmed fish, while fillet accumulations of specific health-related nutrients may simultaneously add value to the final product. This thesis summarizes research undertaken in an effort to enhance the nutritional value of fish by increasing fillet levels of selenium (Se). In addition, various biomarkers of fish health (lysozyme, ceruloplasmin and glutathione peroxidase (GSH-Px) activities), were examined to determine whether dietary Se supplementation had a positive impact upon fish immunocompetence. Moreover, the effect of vaccination was also examined using lysozyme and growth as indicators of fish performance. Hybrid striped bass (HSB), the fourth most valuable farmed fish and fifth in tonnage produced in the United States, were employed as a model animal. Se, an essential component of the antioxidant enzyme, glutathione peroxidase with many established health benefits was supplemented to HSB diets at various concentrations but was found to be without effect upon serum immune proteins or GSH-Px activity. This finding likely reflected the use of fishmeal within the dietary formulation, which possessed relatively high Se levels, together with sufficient storage of tissue Se within the experimental animals. Nevertheless, these studies determined that organic sources of Se were more efficiently accumulated in HSB muscle than traditional inorganic sources. A linear response occurred up to the highest dose used (3.2 mg kg⁻¹) over a 6 week study. Fillet Se accumulation (r²=0.95) proved to be a better indicator than the liver (r²=0.87).Se enhanced fish therefor appear to offer a route of entry for fish producers into the lucrative designer food market - especially since many hundreds of millions of people worldwide are believed to be Se-deficient. Studies undertaken with Se-deficient HSB confirmed findings from the aforementioned research and also indicate that Se-enhanced fillets might be produced using a finishing feed containing 1.5 mg Se kg⁻¹ 6-8 weeks prior to harvest. Accumulation of Se using this strategy resulted in a 100g portion of HSB fillets containing between 33-109 µg Se, amounting to a dietary intake of between 25-80 µg Se; a level that would satisfy present daily intake recommendations. Vaccination of HSB with a Streptococcus iniae oil-in-water vaccine was examined for its potential negative impacts upon HSB production performance. Vaccinated fish did not exhibit any significant reductions in growth but microarray studies revealed that together with many hundreds of genes, four immune-related genes were impacted by this procedure. This thesis discusses the results obtained with regard to their practical implications to the industry and welfare of cultured fish.
Distribution and life history of the endangered James Spinymussel, pieurobema collina (bivalvia: unionidae)
Hove, Mark Curtis (Virginia Tech, 1990-05-05)
Distribution of the James spinymussel (Pleurobema collina) and aspects of its life history were studied from June 1987 to October 1989. Field and laboratory observations were used to determine gravidity and glochidial release periods, fish host requirements, age class structure, growth characteristics, and juvenile survival. Stream surveys conducted at 243 sites in 20 counties revealed new populations of this species in three subdrainages (Catawba Creek, Pedlar River, and Mechums River), of the James River, greatly expanding its known range. Female P. collina were gravid from late May through early August 1988 and 1989 in Craig Creek, Virginia, and the South Fork Potts Creek, West Virginia. Glochidia were released from late June through early July in the South Fork Potts Creek, at mean water temperatures between 21 and 25 °C, and discharges between 0.013 and 0.050 m l/sec. Field observations and laboratory tests confirmed that cyprinids serve as fish hosts for P. collina glochidia. Glochidia of the James spinymussel were identified on the common shiner (Notropis cornutus), rosyside dace (Clinostomus funduloides), bluehead chub (Nocomis leptocephalus), pumpkinseed (Lepomis gibbosus), and fantail darter (Etheostoma flabellare) in the South Fork Potts Creek. Eleven fish families were tested for suitability as fish hosts in the laboratory, but only the following 7 species served as hosts: bluehead chub (N. leptocephalus), rosyside dace (C. funduloides), satinfin shiner (N. analostanus), rosefin shiner (N. ardens), central stoneroller (Campostoma anomalum), blacknose dace (Rhinichthys atratulus), and mountain redbelly dace (Phoxinus oreas). Juvenile P. collina, fed a mixture of three green algae species in chambers with and without silt, lived 50 days. Juveniles in silt grew significantly faster than those not in silt after 18 days. Age and growth characteristics of adults were obtained by thin-sectioning valves collected in muskrat middens in Dicks and Johns creeks, Virginia. Ages ranged between 3 and 19 yr, and a strong year class was identified at age 11. Mean annual mortality rate was calculated to be 9.8%. As predicted by the von Bertalanffy growth equation, P. collina reaches a maximum length of 74.4 mm, and annual growth increments decrease from 7.04 mm/yr (age 1) to 0.88 mm/yr (age 19). As judged by qualitative surveys, current populations of P. collina in Craig Creek, Johns Creek, and the South Fork Potts Creek appear to be self-sustaining. Populations in Catawba and Patterson creeks appear to be small and are probably in jeopardy of being extirpated. The status of the James spiny mussel in Dicks Creek, Rocky Run, and Pedlar and Mechums rivers is unknown since these streams were not extensively surveyed.
Distribution of larval fishes in the Winfield Pool, Kanawha River, and direct impacts of commercial navigation traffic on larval fish survival
Odom, Michael Cooper (Virginia Tech, 1987-09-15)
Distributions of larval fishes in the Winfield Pool, Kanawha River, West Virginia, were determined by sampling two sites with bongo and push nets. Cyprinids, clupeids, and Aplodinotus grunniens dominated collections. Main channel densities were a fraction of the densities along the shoreline, indicating the importance of the shoreline as a nursery. Diel trends in abundance were evident for several taxa, but were likely caused by diel changes in gear avoidance and distribution of larvae. Vertical trends in abundance were apparent for several taxa at the deeper and more lentic sampling site (lower pool). Aplodinotus grunniens were generally more abundant near the bottom, especially during daylight. Cyprinids were more abundant near the bottom in mid-June, but displayed no vertical trends on other sampling dates. Clupeids were more abundant at middepth or surface during daylight, while equally dispersed or near the bottom at night. Vertical trends were not evident at the shallower and more lotic site (upper pool) except for Aplodinotus grunniens, which displayed the same preference for the bottom, as at the lower site.
Ecology of benthic macroinvertebrates in experimental ponds
Christman, Van D. (Virginia Tech, 1991-09-07)
I studied life history parameters of 5 taxa of aquatic insects in the orders Ephemeroptera and Odonata, successional patterns over 2 years of pond development, and precision of 15 biological metrics in a series of 6 replicate experimental ponds from March 1989 to April 1990. I determined voltinism, emergence patterns, larval growth rates and annual production for Caenis amica (Ephemeroptera: Caenidae), Callibaetis floridanus (Ephemeroptera: Baetidae), Anax junius (Odonata: Aeshnidae), Gomphus exilis (Odonata: Gomphidae), and Enallagma civile (Odonata: Coenagrionidae). Growth rates ranged from 0.011 to 0.025 mg DW/d for Ephemeroptera and from 0.012 to 0.061 mg DW/d for Odonata. Annual production ranged from 5 to 11 mg DW/sampler/yr for Ephemeroptera and from 10 to 673 mg DW/sampler/yr for Odonata. Comparison of the benthic macroinvertebrate community at the end of year 1 to the benthic macroinvertebrate community at the end of year 2 showed no significant differences for community summary measures (total density, taxa richness, diversity, Bray-Curtis similarity index); however, some individual taxa densities were significantly lower at the end of year 2. Physicochemical parameters measured indicated that the ponds were oligotrophic. Submerged macrophytes colonized and became established in most of the ponds during year 2. A few noninsect taxa were not present in expected numbers, probably due to lack of efficient dispersal mechanisms. Fifteen metrics were analyzed by a statistical procedure that indicates the percent change that must occur (detection limit) to detect true differences between two means. The metrics with the lowest detection limits (usually < 20%) were taxa richness, EOT index (number of taxa in the orders Ephemeroptera, Odonata, and Trichoptera), proportion of Chironominae/Orthocladiinae, and proportion of collector-gatherers. Detection limits of < 20% on all dates were also obtained for taxa richness and EOT index metrics when analyzed using dip net samples. Density metrics only allowed detection limits of about 50% on most dates. This study provided needed information on the life history of taxa important in shallow, lentic ecosystems, ecological succession in newly created ponds, and statistically sound and ecologically meaningful metrics. This study also provides a valuable baseline for impact assessment work in experimental ponds.
The effects of acid and water hardness on bluegill embryo-larvae determined by laboratory and on-site toxicity tests
Moynan, Kathleen M. (Virginia Tech, 1989-11-15)
The sensitivity of bluegill (Lepomis macrochirus) to low pH in soft (12 or 18 mg/L CaCO₃) and hard (165 or 197 mg/L CaCO₃) water was compared in five day laboratory toxiclty tests. Embryo-larval bluegill were exposed to pH levels ranging from 3.8 to 7.0 in soft water and from 3.8 to 8.0 in hard water. An on-site toxicity test, using lake water (3.4 mg/L CaCO₃) adjusted to pH levels ranging from 3.5 to 7.3, was conducted to compare laboratory and field results. At low pH, hatching was reduced, the hatching period prolonged, and the incidence of partial hatching increased. Increased water hardness mitigated acid toxiclty, enhanced larval survival, and promoted hatchability. Hatching rates were decreased over those of the controls by 76 percent in soft water and by 23 percent in hard water at pH 4.0, and hatching was negligible at pH 3.8. The length of the hatching period was prolonged by 24 to 48 hours at pH levels ≤4.6. Partial hatching averaged 43 percent in pH 4.4. Increasing acidity resulted in increased embryo-Iarval mortality, averaging >62 percent at pH levels ≤4.6; mortality was 100 percent at pH levels <4.4 in soft water and 3.8 in hard water. Bluegill larvae were more sensitive than eggs. The embryo-larval LC50's were pH 4.67 in soft water and pH 4.06 in hard water; LC1's were pH 5.66 in soft water and 5.04 in hard water. In the on-site field experiment, approximately 50 percent mortality occurred at pH 4.6 which was nearly identical to the LC5O of pH 4.67 in laboratory (soft water). Growth of larvae was not affected by low pH. As acid levels increased, yolk-sac volumes decreased, physical deformities (fin, eye, and spinal abnormalities) increased and behavioral abnormalities were evident. Yolk-sac volume was decreased at pH levels <5.5 in soft water and <5.1 in hard water, perhaps reflecting higher energy expenditures by larvae held at sublethal pH levels. Spinal curvature and fin erosion of larvae were apparent at pH levels <5.25 in soft water. Larvae were lethargic and swimming ability was impaired at pH levels ≤5.5 in soft water and ≤5.1 in hard water. Exposure of embryo-larval bluegill to low pH levels (<5.7) in soft water may compromise their ability to survive, forage efficiently, and escape predation under natural conditions.
Effects of liming on plankton and young-of-the-year bluegill growth in Flat Top Lake, West Virginia
Coahran, David Alan (Virginia Tech, 1990-01-15)
The responses at three trophic levels (phytoplankton, zooplankton, young-of-the-year bluegill) were compared between a limed and unlimed arm in a moderately fertile, circumneutral reservoir that was sensitive to acidification, but had not yet shown signs of damage. The east arm (25.5 ha) of Flat Top Lake was treated with 28.8 dry metric tonnes of calcite using slurry box technology between July 13-20, 1987. The design was confounded because calcite dissolution products diffused into the unlimed (west) arm after the treatment which made total alkalinity similar between the arms within 1 month. Phytoplankton gross productivity and chlorophyll a was similar between the arms for the pre- and post-treatment samples as well as for the period after the treatment when total alkalinity was relatively higher in the limed arm. Zooplankton biomass was higher in the unlimed than limed arm in the pre-treatment samples but was similar between the arms in the post-treatments samples; however, the changes in zooplankton biomass after treatment in the limed arm could not be attributed to the treatment. Phytoplankton community composition for the common netplankton and nannoplankton was similar between the limed and unlimed arms for the combined pre- and post-treatment samples: however, Gemellicystis spp., Gloeocystis spp., and Dinobryon spp. showed an order of magnitude higher density in the limed relative to the unlimed arm on the initial post-treatment sample. This difference, as well as the observed post-treatment differences in zooplankton community composition between the two arms could not be attributed to the treatment because there were minimal impacts on nutrient levels (e.g., CO2, total phosphorus) and zooplankton-phytoplankton interactions. Lake transparency was significantly deeper in the limed arm relative to the unlimed arm for the post-treatment samples; however, a corresponding lower dissolved organic carbon concentration was not measured in the limed arm. Young-of-the-year bluegill (e.g., primarily those 15-20 d old) showed significantly higher growth rates in the unlimed arm during the period when total alkalinity was higher in the limed arm, apparently due to a higher density of suitable pelagic zooplankton in the unlimed arm during this period. In conclusion, no significant positive or negative responses to the treatment were detected because of trophic level interactions. The high pre-treatment pH (7.07), small change in post-treatment pH, low dissolution percentage (8-10%), the inability of the sediment dose to neutralize the acidic sediments and induce phosphorus release, and phosphorus rather than carbon dioxide limited primary productivity were the main factors why no significant post-treatment biological responses were detected.
Effects of sewage treatment plant effluents on mollusks and fish of the Clinch River in Tazewell County, Virginia
Goudreau, Stephanie E. (Virginia Tech, 1988-09-05)
The Clinch River is renown for its rich mollusk and fish assemblages, including many endemic species. New sewage treatment plants (STP's) have recently been constructed along the Clinch River in Virginia, raising concern because of the disappearance of mollusks below existing STP's. Field and laboratory studies were conducted to determine mollusk and fish distribution in proximity to two STP's in Tazewell County, and the tolerance of two mollusk species to mono chloramine and unionized ammonia, the major toxicants in domestic STP effiuent. River reaches up to 3.75 km downstream of the STP outfalls at Tazewell and Richlands were depauperate of mussels. Tolerance to effluent seemed to vary among snails, sphaeriid clams, and the Asiatic clam Corbicula flumineaK. After an initial toxic zone below the Tazewell outfall, abundance of fish appeared to increase by 0.45 km below the outfall. The effluent at Richlands eliminated intolerant species, and more tolerant species were present as far as 0.45 km below the outfall. Laboratory bioassays with glochidia of Villosa nebulosa resulted in 24-h EC₅₀ and LC₅₀ values of 0.042 and 0.084 mg/L monochloramine, respectively, and 24-h EC₅₀ and LC₅₀values of 0.237 and 0.284 mg/L unionized ammonia, respectively. Glochidia rank among the most sensitive invertebrates in their tolerance to these toxicants. The snail Pleurocera unciale unciale was moderately sensitive, with 96-h LC₅₀ values of 0.252 mg/L mono chloramine and 0.742 mg/L unionized ammonia. Comparison of monochloramine and unionized ammonia concentrations monitored at 0.10 km below the outfalls indicated that mono chloramine was the major toxicant likely affecting fauna.
Evaluating the effects of angler behavior on the efficacy of harvest regulations in recreational fisheries
Creamer, Allan E. (Virginia Tech, 1993-01-05)
A computer-implemented simulation model was modified to compare various regulation schemes and determine how they are affected by angler non-compliance and voluntary catch-and release fishing. Combinations of three creel limits and five length limits were simulated. Scenarios for no regulations and catch-and-release were also simulated. Angler noncompliance varied from 0% to 50% and voluntary release included rates of 20%, 50%, and 80%. Based on catch, harvest, yield, and PSD, the ranking of specific regulations changed little among levels of angler non-compliance and voluntary release. All four decision variables were most influenced by regulations when angler compliance was high and voluntary release was low. Further, for a fishery with a high degree of voluntary release, and relatively high angler compliance, regulations did not produce any discernible benefits in the fishery. The model was demonstrated with data on a smallmouth bass, Micropterus dolomieu, fishery for the upper and lower James River, Virginia. Simulated regulations were assessed based on adjustments to angler non-compliance, which averaged based on adjustments to angler non-compliance, which averaged 17 percent, and voluntary release, which averaged 90 percent. Model results indicate that more restrictive regulations improved PSD and catch, whereas numerical harvest and yield in weight benefitted from liberal regulations. Variability among the 81 regulations was low, suggesting that voluntary release (90% average) is a dominant control in the James River smallmouth bass fishery. From a management standpoint, these findings also suggest that, where appropriate, management strategies should focus on increasing voluntary release and rely on regulations only in certain fisheries.
Evaluation of ceftiofur sodium as a chemotherapeutic agent in grass carp (Ctenopharyngodon idella)
Somjetlertcharoen, Amornchai (Virginia Tech, 2001-03-23)
Ceftiofur sodium, a third generation cephalosporin, was studied to determine the potential of this drug as an alternative bacterial therapeutic agent for the aquaculture and ornamental fish industry. Grass carp, Ctenopharyngodon idella have been selected as the fish model for this study since they are a good representative for both foodfish and ornamental fish and are one of the major species grown worldwide. Pharmacokinetics of ceftiofur sodium after various routes of administration, histopathologic observations to detect possible toxic effects on the tissues involved in its metabolism and excretion, and the effects on the non-specific immune response were investigated in grass carp. For the pharmacokinetic studies, ceftiofur sodium was administered a single time to grass carp by four different routes : intracardiac (IC), intraperitoneal (IP), intramuscular (IM) and oral (PO) at a dosage of 8 mg/kg body weight. Serial blood samples were obtained and plasma samples were analyzed by high performance liquid chromatography for ceftiofur (as measured its metabolite, desfuroylceftiofur (DFC) and DFC-related metabolite concentrations). Disposition pharmacokinetic data were best described by a two compartment open model for IC and by a non-compartment model with no lag time for IP and IM administrations. Oral absorption of ceftiofur was not observed in this species. Following IC, IP and IM ceftiofur sodium administration, the final elimination half-lives, maximum plasma concentration, time to reach maximum concentration, volume of distribution and plasma clearance were 0.38, 0.45 and 13.86 hours ; 157.09, 31.54 and 8.86 mg/ml ; 0, 0.25 and 0.5 hours ; 0.09, 0.17, 0.53 l/kg ; and 0.21, 0.26, 0.26 ml/min.kg, respectively. Desfuroylceftiofur metabolite was highly bound with plasma protein at pH 7.0 and 8.0. For the histopathological studies, a single intramuscular dose of ceftiofur sodium at three different concentrations, 8 (1X), 40 (5X) and 80 (10X) mg/kg was administered to separate groups of grass carp for evaluation of the potential toxicity to major tissues involved in metabolism and excretion of this drug. These included the anterior kidney, posterior kidney, liver, and spleen. After 48 hours, lesions were seen in the posterior kidney at the highest dose of ceftiofur (10X). Morphological alterations observed microscopically included increased number of renal tubules, tubular necrosis and infiltration of inflammatory cells. No adverse effects on the glomeruli were observed at any concentration of the drug. For the immunotoxicity studies on the non-specific immune response, dosages of either 8 or 40 mg/kg body weight were administered intramuscularly. After 24 and 48 h, leukocyte number, phagocytic ability and H2O2 production were examined in the cells of the pronephros. The results showed that neither dosage had an effect on the number of leukocytes in the pronephros. Phagocytosis was also not significantly altered at either dosage in macrophages from the pronephros. Hydrogen peroxide production was not altered in the pronephros of fish dosed at 8 mg/kg, while at a dosage of 40 mg/kg, H2O2 production was significantly increased. In summary, ceftiofur sodium has potential as an efficacious chemotherapeutic agent for controlling bacterial infection in brood stock and ornamental fish at the recommended dose of 8 mg/kg. A dose as high as 40 mg/kg can be use with careful consideration. This dosage may not directly injure the posterior kidney but it may affect the non-specific immune response of the fish.
Evaluation of ozone treatment, pilot-scale wastewater treatment plant, and nitrogen budget for Blue Ridge Aquaculture
Sandu, Simonel Ioan (Virginia Tech, 2003-04-04)
Sustainable tilapia production at Blue Ridge Aquaculture (BRA) is constrained by availability of high quality replacement water. I developed a pilot-scale wastewater treatment system to treat and reuse effluent presently discharged. An initial study was conducted to determine the response of the BRA waste stream to ozone application. Dosages of 6.9, 4.8 and 2.4 g O3 were applied for 30 minutes to 35 L of settled effluent. Optimum ozone dosage and reaction time, ozone transfer efficiency, ozone yield coefficient, degree of pollutant removal, and other ozone and water quality parameters were determined. Most results suggested that the maximum process feasibility limit for ozone contact time was approximately 9 minutes at an applied ozone concentration of 23g/m3 (6.9 g O3 dose). Formation of foam increased solids and COD removal up to three times. Poor removal or accumulation of DOC and TAN was observed, indicating the need for biological treatment following ozonation. Next, I evaluated a pilot station treatment train including sedimentation, microscreen filtration, fluidized bed denitrification, ozonation, aerobic biological oxidation in a trickling filter, and jar-test chemical flocculation. Significant improvements were found regarding solids, COD, cBOD5, NO3--N, TKN, and turbidity. Removal of foam after ozonation improved ozonation efficacy and pollutant removal. A nitrogen budget for the BRA facility was derived, indicating that 35% of the nitrogen applied in feed was assimilated in fish. I evaluated the possible impact of residual inorganic nitrogen forms from treated effluent upon fish in the recirculating systems. I found that less than 1% of the TAN produced would return the recovered stream, and that the existing biological contactors can remove it. Evaluation of TAN fate indicated that 84% was oxidized in biofilters, 14% was oxidized by passive nitrification, and 1% was removed by water exchange. For NO3-N, I determined that 56% was removed by passive denitrification and 44% by daily water exchange. The pilot station design was effective for removing organics and nutrients, and can serve as the basis for scale-up for treating and reusing the entire BRA effluent stream.
Experiments to culture juvenile freshwater mussels in small tanks, floating containers and sediment beds
Yang, Cheng-liang (Virginia Tech, 1996)
Freshwater mussel culture has become an attractive enterprise because of its application for restoring depleted freshwater mussel populations, for rearing adults to support shell and cultured pearl industries, and for environmental monitoring and assessment. This study focused on testing indoor and outdoor culture techniques to rear newly metamorphosed juveniles of the rainbow mussel (Villosa iris). Tanks and floating containers were used outdoors, and sediment beds and floating containers were used in indoor culture experiments. Culture experiments with indoor sediment beds produced modest growth rates and variable survival rates for up to 4 months. Shell lengths of juveniles increased from 0.38 - 0.41 mm to 0.93 - 3.22 mm, 1.45 - 7.05 times original size; survival rates ranged from 1.27 % to 51.0 %. Experiments with indoor floating containers resulted in an increase of juvenile shell lengths from 0.38 - 0.40 mm to 0.86 - 2.07 mm, an 86 - 207 % increase; survival rates were 23.3 % to 27.0 % after 3 months. All indoor culture experiments combined water flow, inoculation of algae, fertilization, lighting and a pre-operation phase. Experimental results suggested that indoor floating container culture was a useful method to rear newly metamorphosed juvenile mussels, and the indoor sediment bed culture technique may also be suitable with modification, especially if filamentous algae can be controlled. Both outdoor tank and floating container culture experiments yielded poor results, which were probably caused by unsuitable culture conditions. Differences in juvenile growth rates (P < 0.001) and survival (P < 0.001) between floating container experiments I and II, which used the same culture techniques, were attributed to differences in culture conditions; water temperature (P < 0.001), dissolved oxygen (P < 0.01) and hardness (P < 0.01). Water temperature also contributed to a higher growth (P < 0.001) and survival rate (P < 0.001) in sediment bed culture II. The extensive occurrence of filamentous algae on sediments affected results and caused lower growth (P < 0.001) and survival rates (P <0.001) of juveniles in the sediment bed culture experiment III, IV and V. Finally, absence of water flow may have influenced growth and survival of juvenile V. iris, a naturally riverine species. Lack of currents near the bottom of tank and floating containers where juveniles resided likely contributed to complete mortality of juveniles in the outdoor culture experiments.

Browsing by Author "Helfrich, Louis A."

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