Browsing by Author "Libey, George S."

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    Aquaculture of Pacu (Piaractus mesopotamicus) and a Comparison of its Quality: Microbiological, Sensory, and Proximate Composition
    Pullela, Sharma V. S. (Virginia Tech, 1998-08-21)
    (Piaractus mesopotamicus) initially weighing 72.0 g were fed three diets - a) 0.5% vegetable (zucchini), b) commercial 32% (P32) and c) commercial 36% (P36) protein diets for 24 weeks and their growth performance compared. Processing yields and proximate composition were determined following dressing of pacu. The microbiological quality of pond cultured pacu was compared to aquacultured hybrid striped bass, tilapia, and rainbow trout grown in pond and recirculating aquaculture systems. Sensorial analyses for differences in flavor, preference, and color were also determined. Protein concentration significantly influenced the weights, lengths, specific growth rate, feed conversion ratio, and protein efficiency ratio (p < 0.05). Diet insignificantly influenced the processing yields (p > 0.05). The moisture, protein and total lipid contents were significantly affected (p < 0.05) by the dietary protein. The indicative bacterial quality differed significantly for pacu as well as the water used for culturing pacu (p < 0.05) among dietary treatments. Aquaculture production systems significantly influenced the indicative and pathogenic bacterial quality. Listeria monocytogenes, Salmonella spp., Yersinia enterocolitica, and Escherichia coli O157:H7 were not isolated from any of the sampled fish. The qualitative and quantitative results of Clostridium botulinum were influenced by the production system (p < 0.05). Flavor of pacu was comparable to that of hybrid striped bass, tilapia, and rainbow trout, but superior to catfish. Cooking significantly improved the color of the ground fish fillets.
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    A Comparative Analysis of Three Biofilter Types Treating Wastewater Produced in Recirculating Aquaculture Systems
    Hall, Antar Gamble (Virginia Tech, 1999-12-01)
    Nine recirculating systems at the Virginia Tech Aquaculture Center were placed on line and stocked with yellow perch, Perca flavescens, fingerlings. Fish were stocked at a density of approximately 455 fish m³. Biofilter types were the only factor differing among system designs and were an upflow pulsed bed bead filter, packed tower trickling filter and a rotating biological contactor (RBC). After stocking, systems were allowed to acclimate using ammonia excreted by the yellow perch. Following acclimation, a comparative analysis on biofilter performance began. To evaluate filter performance, water quality parameters tested were temperature (°C), pH, dissolved oxygen (DO), total ammonia-nitrogen (TAN), nitrite-nitrogen (NO₂⁻-N), nitrate-nitrogen (NO₃⁻-N), alkalinity (as CaCO₃), water hardness (as CaCO₃), carbonaceous biochemical oxygen demand (cBOD₃), dissolved organic carbon (DOC), and total suspended solids (TSS). Basic water quality analysis encompassed samples drawn at 8 AM. TAN mass removal analysis encompassed water quality samples drawn at 8 AM and over 24 hours. Higher TAN mass removal rates were achieved in trickling and RBC filters than in bead filters for 8 AM (0.037, 0.14, and 0.004 g/m²/d, respectively) and diurnal sample periods. Analysis of areas under mass removal curves depicted RBC filters as surface area limited. Trickling filters proved most effective at carbon dioxide stripping and pH maintenance and also effectively removed TSS from the culture water. The study did not show filter type as having a significant effect on median organic water quality parameter values.
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    Comparative Growth of All-Female Versus Mixed Sex Yellow Perch (Perca flavescens) in Recirculating Aquaculture Systems
    Schmitz, Mark Harvey (Virginia Tech, 1999-05-20)
    Nine, production-scale, recirculating aquaculture systems were utilized to compare the growth parameters between all-female and mixed sex yellow perch stocks. Each system was stocked with 455 fish m⁻³ and contained one of three different biofilter types: a rotating biological contactor, a trickling filter or a bead filter. The all-female fingerlings (S1) used were originally derived from Lake Mendota, Wisconsin. The mixed-sex fingerlings (S2) used were originally derived from Lake Erie. Temperature and photoperiod (23°C, 16H-L) were maintained at levels for optimal growth. Absolute growth rates ranged from 0.27-0.48 g/day. Mean final density within treatments was 42.8 kg/m³ and ranged from 37.2-50.2 kg/m³. The main effect of stock did not have a significant effect on growth (p > .1). All-female treatments exhibited more uniform growth. The main effect of filter type did have a significant effect on fish growth (p < .01), with fish in tanks containing trickling filters exhibiting significantly higher growth. Total feed conversion averaged 1.61 across all treatments and ranged from 1.38-1.78. S1 treatments consumed a significantly higher percent body weight per day than S2 treatments (p < .05). Analysis of PIT tagged individuals revealed that the mean relative growth rate was significantly higher in S2 individuals (513.9%) compared to S1 individuals (315.3%: p < .01). S2 females (597.8%) grew 1.9 times faster than S1 females (315.3%: p < .01). Within S2 individuals, females (597.8%) grew 1.5 times faster than males (395.2%: p < .05). For all individuals, 33.6% of the variation in final weight was explained by the variation in initial weight. Differences in the geographic strain or culture history of these stocks may have had a larger overall effect on growth than sexual classification (all- female or mixed sex). Dress percentage of skin-on butterfly fillets was examined in 20 individuals per stock and in six groups of 20 individuals per stock. Within S2 individuals, 73.7% were female. Mean fillet yield was significantly greater in S1 individuals (47.6%) compared to S2 individuals (43.0%: p < .01). Mean GSI in S1 individuals (1.01%) was significantly higher than S2 individuals (0.54%: p < .05). Within S2 individuals, mean GSI was significantly higher in females (0.70%) when compared to males (0.08%: p < .05). Fillet yield was significantly greater in S1 groups (47.2%) compared to S2 groups (44.9%: p < .01). Within each stock fillet yield increased with size. The difference in fillet yield demonstrated between these stocks may be a result of differences in strain of origin. The identification of superior yellow perch strains or strain crosses with regard to growth rate and fillet percentage is of considerable importance to the industry.
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    Comparison of Growth, Feed Conversion and Survival of Morone saxatilis female x M. mississippiensis male and M. saxatilis female x M. chrysops male Hybrids Reared in Recirculating Aquaculture Systems
    Bosworth, B. G.; Libey, George S.; Wolters, W. R. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2001-06-01)
    Striped bass female (M. saxatilis) x white bass male (M. mississippiensis), (SBxWB, n = 300) and striped bass female x yellow bass male (M. chrysops) (SBxYB, n = 300) fingerlings, initial mean weight 91 g and 62 g, respectively, were reared in recirculating aquaculture systems at densities of 118 fish/m3 for 120 days. Mean weight increased 309 g and 151 gin SBxWB and SBxYB, respectively. ,final mean weight and total length, and rate of weight and length increase were higher for SBxWB than SBxYB. Condition factor and survival were higher for SBxYB (1.04 and 99.3%, respectively) than for SBxWB (1.01 and 96.0%,respectively). Mean feed conversion ratio (FCR) was lower for SBxWB (1.4) than for SBxYB (1.6). Significant time x hybrid interactions indicated that growth rate of SBxYB improved, relative to SBxWB, as the study progressed. Positive linear trends for total ammonia, unionized ammonia, and nitrite indicate water quality deteriorated as the study progressed. Time x hybrid interactions for growth rate may have been due to differential responses of SBxYB and SBxWB to deterioration of water quality. Although SBxYB had slightly better survival than SBxWB and their growth rate improved relative to that of SBxWB, the slow overall growth of SBxYB limits its potential for recirculating system production.
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    Comparisons of tilapia seed production under various broodstock densities and fry stocking densities
    Glenney, Gavin W. (Virginia Tech, 1996-12-10)
    Four methods of seed (eggs, sac-fry, and fry) production for Rocky Mt. White hybrid® tilapia, (0. niloticus x O. aureus), were compared under green water conditions over a six month period in an environmentally controlled greenhouse at the Virginia Polytechnic Institute and State University's Aquaculture Research Laboratory. Twelve 3 m2 rectangular tanks were stocked with brood stock (mean wt. 680 g), at a sex ratio of 3 females to 1 male. Nine tanks were stocked at one of three densities (1, 2, and 4 females m-2), and seed was collected from females' mouths weekly. Three additional tanks were stocked at a density of 2 females m-2, and fry were collected from the edges of the tanks when seen. Seed production was among the highest seen for related studies. Average number of viable fry produced at I females m-2, 1660 fry female- I month-I, was significantly higher than the combined average production of densities 2 females m-2 (629 fry female- I month-I) and 4 females m-2 (695 fry female-1 month- 1) (p< 0.02). Even though there was no significant difference between viable fry production meter-2 (p>0.05), the highest density consistently produced more fry meter-2. No significant difference was observed in viable fry production between the two seed collection methods (Clutch removal- 629 fry female-1 month-I; Natural mouth-brooding- 520 fry female-1 month-I) (p>0.05). The effects of stocking density on growth and survival were evaluated by stocking 14-16 day old artificially incubated fry (25.5 ± .32 mg, 12.1 ± .04 mm), into 150 liter troughs at three densities (3, 6, and 12 fry liter-I) under green water conditions for 30 days. The mean monthly hatchery seed survival was 65.7 ± 2.3%, which varied largely depending on initial seed developmental stage. Significant differences were observed between mean weight, length, survival, and feed conversion ratios among the various fry stocking densities (p
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    Comparisons of Tilapia Seed Production Under Various Broodstock Densities and Fry Stocking Densities
    Glenney, G. W.; Libey, George S. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2002-06-01)
    Three types of seed (eggs, sac-fry, and fry) production for Rocky Mountain White® hybrid tilapia, (O. niloticus x O. aureus), were compared under green water conditions over a six-month period in an environmentally-controlled greenhouse at the Virginia Tech Aquaculture Center. Rectangular tanks were stocked with broodstock (mean wt. 680 g), at a sex ratio of 3 females to 1 male. Nine tanks were stocked at one of three densities (1, 2, and 4 females/m2), and seed was collected from the females' mouths weekly. Three additional tanks were stocked at a density of 2 females/m2, and fry were collected from the edges of the tanks daily. Average number of viable fry produced by the clutch removal method at 1 female/m2 was significantly higher than the combined average production of densities at 2 and 4 females/m2 (p< 0.02). Even though there was no significant difference between viable fry production per meter sq. (p>0.05), the highest density consistently produced more fry/m2. No significant difference was observed in viable fry production between the clutch removal method and the natural mouth-brooding method (p>0.05). The mean monthly hatchery seed survival was 65.7 ± 2.3%, which varied largely depending on initial seed developmental stage. The effects of stocking density on growth and survival were evaluated by stocking 14-16 day old artificially incubated fry (25.5 ± 0.32 mg, 12.1 ± 0.04 mm), into 150-liter troughs at three densities (3, 6, and 12 fry/ liter) under green water conditions for 30 days. Significant differences were observed between mean weight, length, survival, and feed conversion ratios among the various fry stocking densities (p<0.05).The greatest growth was at a density of 3 fry/liter, while survival was not affected until a density of 12 fry/liter was reached. These results suggest that to maximize fry production and reduce labor, a density of 4 females/m2 or higher be used under the natural mouth-brooding seed collection method. They also suggest a fry stocking density between 6 to 12 fry/liter should be used with periodic grading or sex reversal to reduce cannibalism and increase growth.
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    A computer simulation model for wastewater management in an integrated (fish production-hydroponics) system
    Singh, Sahdev (Virginia Tech, 1996)
    Intensive fish production in a recirculating aquaculture system facility is a complex bioengineering operation involving a sensitive balance among physiological, water quality, and management components of the overall system. Warm and nutrient-rich wastewater discharged from controlled-environment fish production facilities is a loss of heat energy and nutrients in addition to being potentially harmful to the environment. The operators of such systems need sophisticated management tools if the operation is to be both commercially successful and environmentally friendly. Effluent heat and nutrients can be recovered using hydroponics in a greenhouse attached to the recirculating aquaculture system facility. A computer model was developed to simulate system performance and to help determine design parameters for an integrated fish production-hydroponics system. The aquaculture component of the model predicts (a) fish growth-dependent feeding, (b) diurnal metabolic waste production/accumulation in the fish culture water, and (c) quality, quantity and frequency of wastewater discharge. The hydroponics component computes optimum greenhouse size and models the performance of vegetable plants in terms of nutrient-uptake, water use, and growth. SUCROS and TOMGRO, plant growth models with modifications for water use and nutrient uptake, were used to simulate lettuce and tomato performance, respectively. To validate the plant models, experiments were conducted in a greenhouse utilizing aquacultural wastewater as the hydroponic solution to produce lettuce and tomatoes. Plant growth, water quality (nutrient-uptake), water use, and environmental conditions were monitored. Lettuce and tomato growth was accompanied with significant reductions in nitrogen and phosphorus levels of the wastewater. Water use by plants strongly depended on solar radiation and plant growth stage. At harvest, nine-week-old lettuce weighed 160 g/plant (average) at a density of 40 plants/m². Tomato yielded 2.4 kg/m² after 17 weeks. However, the tomato fruits did not reach maturity during this time. After 20 weeks, the tomato yield was 3.1 kg/m² and some fruits showed maturity. The use of the model as a management tool for making decisions on optimum greenhouse area for a given recirculating aquaculture system size is demonstrated. The effect of fish stocking density and greenhouse heat loss factor on the optimum greenhouse size are also demonstrated. For an optimum greenhouse size, water use and nutrient-recovery from the effluent by lettuce and tomato plants are quantified.
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    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.
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    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.
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    Denitrification of Recirculating Aquaculture System Waters Using an Upflow Biofilter and a Fermented Substrate
    Phillips, Jennifer Brooke (Virginia Tech, 1997-12-17)
    The ability of an upflow, denitrifying biofilter using a fermentation generated carbon source to treat the high nitrate concentrations typically seen in recirculating aquaculture systems was studied using a synthetic nitrate wastewater supplied at two nitrate loadings, 1.13 and 2.52 kg NO3-N/m3/day. A supplemental carbon source was provided primarily through the fermentation of fish food which generated volatile fatty acids (VFA) in the form of acetic, propionic, isobutyric, n-butyric, 2-methylbutyric, 3-methylbutyric, and n-valeric acids. Acetic and propionic acids were the predominant constituents generated, while lower concentrations of the longer carbon chain butyric and valeric acids were produced. The VFAs proved to be a viable carbon source for the denitrification process as indicated by the ability of the biofilm to assimilate all of the constituents generated. Carbon limiting the system resulted in an increase in effluent nitrite and incomplete nitrate removal. During the low nitrate loading condition, influent COD to NO₃-N ratios greater than 5 typically achieved high total nitrogen removals greater than 95%. This influent ratio corresponded with a COD to NOx -N consumption ratio of 4.62 ± 0.28 mg/L as COD per mg/L as N for complete nitrogen removal. Under the high nitrate loading condition, influent COD to NO₃-N ratios achieving high nitrogen removals showed great variability and did not correspond to a distinct value. The COD to NOx -N consumption ratios were often below stoichiometric values, which was attributed to the hydrolysis of influent fermentation solids captured within the column to generate a COD source not measured by filtered samples. The column biofilm kinetics were modeled using a half-order reaction rate and denitrification coefficients (k) of 0.70 ± 0.02 (mg NOx-N/L)1/2 / min and 1.18 ± 0.12 (NOx-N /L)1/2 / min were determined for the low and high nitrate loading phases, respectively.
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    Development of a diet for rearing juvenile freshwater mussels
    Gatenby, Catherine M. (Virginia Tech, 1994-04-15)
    Over 100 species of freshwater mussels (Unionidae) are endangered or threatened in the United States, and another dozen species support a declining commercial harvest of shells for the cultured pearl industry in Asia. Because of these Significant declines in abundance, a study was undertaken to develop a diet for rearing juvenile mussels, with the goal of long-term propagation of rare species. Three trials were conducted to test various tri-algal and commercial diets and to determine the influence of silt in survival and growth of the rainbow mussel (Villosa iris) and giant floater (Pyganodon grandis). After 45 days post-metamorphosis, juvenile V. iris fed algae with silt exhibited a two-fold increase in shell length (532 μm), and 63.5% survival. Juvenile P. grandis exhibited similar results at 45 days post-metamorphosis. In comparison, all juvenile mussels fed algae without the presence of silt exhibited no increase in shell length after 45 days post-metamorphosis. However, survival varied between species. Survival after 45 days was 5.0% for V. iris and 43.3% for P. grandis. P. grandis is probably more tolerant of a variety of environmental conditions. Analysis of covariance showed that growth rate over time (120 days) of P. grandis was significantly greater than that of V. iris. Shell lengths of P. grandis juveniles fed algae in the substrates kaolin, sterilized silt, sterilized silt plus Aqua Bacta-Aid, and bacteria-colonized silt were Similar, indicating that bacteria were not essential to juvenile digestion or nutrition. Shell lengths of V. iris juveniles fed algae in kaolin or algae in bacteria-colonized silt also were similar after 60 days. Juvenile mussels appear to be pedal-feeding for approximately 120 ± 30 days, depending on the species; hence, silt probably serves as a physical substratum for pedal-feeding mussels to collect food particles. Subsequent tests indicated that growth was significantly correlated with algae high in oils which contain polyunsaturated fatty acids (PUFA). V. iris juveniles fed a tri-algal diet, consisting of Neoehloris oleoabundans~ Phaeodactylum tricornutum, and Bracteacoccus grandis (NPB), with silt substratum showed the best growth over time. Individuals achieved a mean shell length of 1747 μm and had 30.0% survival after 140 days postmetamorphosis. All other tri-algal diets tested enhanced growth over the commonly used green tri-algal mix of Chlorella, Ankistrodesmus, and Chlamydomonas (CAC), and all algae diets enhanced growth over a silt-only diet. Commercial yeast diets did not support growth. After 272 days post-metamorphosis, V. iris fed CAC in silt achieved a maximum shell length of 4520 μm (17-fold increase in length), with a mean length of 2968 μm and approximately 5% survival. After 195 days postmetamorphosis, P. grandis achieved a maximum shell length of 7846 μm (22- fold increase in length), with a mean of 4877 μm and approximately 12% survival. Results of all feeding trials indicate that algae are a suitable food source for rearing early juvenile freshwater mussels. A tri-a1gal diet high in oils resulted in greater growth than all other diets tested. Resident bacteria in riverine sediments were not essential to growth and survival of juvenile mussels. Silt provided some nutritional value, but primarily served as a physical substratum for pedal-feeding juveniles.
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    Development of juvenile culture techniques and testing of potential biomarkers of environmental stress in freshwater mussels (Bivalvia: Unionidae)
    Beaty, Braven B. (Virginia Tech, 1999-04-22)
    The freshwater mussel fauna of the Clinch River in Southwest Virginia has declined in recent decades, principally due to habitat degradation from poor land-use patterns and pollutants. A study was undertaken to determine the feasibility of using river water in a flow-through culture system to rear juvenile freshwater mussels. The culture method placed juvenile mussels, confined in small dishes, into oval troughs supplied with untreated river water. Two of three years produced acceptable survival rates of 27% and 19% to an age of 90 days or greater. The third year yielded very low survival rates of less than 3%, demonstrating that failures in culture production can occur. Growth rates of juveniles in the culture system using river water were almost double those in laboratory culture systems, provided that juveniles were placed in the oval troughs during June. Otherwise, growth was comparable to that attained in laboratory culture systems.
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    The effects of ozone treatment on chemical parameters of a recirculating aquaculture system producing hybrid striped bass
    Herbst, Jennifer Lynn (Virginia Tech, 1994-08-05)
    The hypothesis tested in this study is that the application of ozone to reuse aquaculture water provides more favorable conditions for hybrid striped bass at production levels. Evaluation of water quality in fish culture systems being treated with ozone was made during a production trial (1200 fish/14,OOO 1). Originally, a control and four ozonated systems with doses of 3, 13, 25, and 45 g O3/kg feed/day supported fish for experimentation but, due to mechanical failure, only the control, the 13 and 25 g O3/kg feed/day treatments completed the full 35 week study. On an equal feeding basis, concentrations of dissolved organic carbon (DOC), carbonaceous biochemical oxygen demand (CBODs), and chemical oxygen demand (COD) were lowest in the most heavily ozonated systems. Ozone increased the biodegradation of DOC. Total suspended solids, particle size and distributions were impacted by ozone's flocculating properties. The percentages of particles in the smallest size range, 5-20 microns, were greater in the control system than the ozonated systems during weeks of equal feeding rates. When feeding rates differed, the control system maintained a larger number total particles per kilogram of feed administered. The pH of the ozonated systems was lower than the control which favored the ionized (less toxic) form of ammonia. Enhanced biodegradation of organics in the ozonated systems may have increased carbon dioxide production and caused a decline in pH. Greater nitrification in the ozonated systems may have also decreased the pH. Higher total ammonia nitrogen (TAN) levels were produced in the control on an equal feeding basis. Average weekly TAN t unionized ammonia (NH3), nitrite and nitrate concentrations remained at acceptable levels across treatments and throughout the production trial. Overall, the major indication of improved system conditions due to ozone treatment was that fish raised in the ozonated systems fed steadily throughout the growth trial while the control system's culture experienced periods of reduced feeding.
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    The effects of temperature, water quality and culture conditions on the immunology, hematology, and blood chemistry of hybrid striped bass
    Hrubec, Theresa (Virginia Tech, 1994-12-19)
    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.
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    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.
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    Genetic marker frequency differences among strains of goldfish, Carassius auratus
    Borkholder, Brian D. (Virginia Tech, 1993-02-02)
    Starch gel electrophoresis and DNA fingerprinting were used to assess molecular genetic variation within and between strains of goldfish, Carassius auratus. Genetic variation observed both within and between strains was low using both methods. using isozyme markers, mean heterozygosity (0.0% - 4.4%) and percent polymorphic loci (0.0% - 30.6%) within strains were low compared to other vertebrate species. Analysis of the isozyme data using Chi-square tests against Hardy-Weinberg genotype expectations and wright's (1943, 1951) F statistics indicated modest heterogeneity in genotype frequencies between strains. DNA fingerprint band sharing values were determined both within and between strains of goldfish. Mean band sharing values within strains were high (68.0% -97.6%), comparable to values observed in highly inbred populations of other vertebrates. Levels of band sharing between strains were determined using a DNA mixing procedure. Band sharing values between strains (57.7% - 100%) were higher than those observed between strains of other domesticated species. Analysis of DNA fingerprint data using ANOVA indicated no significant differences between strains, suggesting that the fancy strains did not exhibit significant differentiation as manifested in DNA fingerprint phenotypes.
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    Growth and Production Characteristics of Palmetto Bass (Morone saxatilis female x Morone chrysops male) Reared at Three Densities in a Pilot-scale Recirculating Aquaculture System
    Brazil, B. L.; Nunley, Chad E.; Libey, George S. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2001-06-01)
    Production characteristics of palmetto bass (Morone saxatilis female x Morone chrysops male) reared at three stocking densities (36 fish/m3, 72 fish/m3, and 144 fish/m3) in a pilot-scale RAS were evaluated. A final mean ±SE fish weight of 412.1 ± 7.8 g at the high density was significantly lower than that of fish at the medium density weighing 542.1 ± 11 .8 g (P < 0.05). Fish weight (676.1 ± 17 .0 g) at_ the lowest density was significantly higher than at the high and medium densities (P < 0.05). The average daily weight gain at the low density (2.8 g/d) was 22% and 47% higher than fish reared at the medium and high densities, respectively. Total biomass gains of 733.8, 483.3, and 297.9 kg were obtafued at the high, medium, and low densities. Feed conversion and survival rates were similar among densities averaging 1.4 and 97 .1 %, respectively. Higher mean daily and cumulative feed totals at the highest density contributed to significantly higher ammonia and nitrite concentrations and lower pH levels at haryest. All other measured water quality parameters were similar among densities and remained within known acceptable limits for fish growth. The results indicated that palmetto bass reared in closed systems reached market size in 224 days at the low and medium densities. However, the relative biomass production may not justify such strategies when compared to the yield obtained at the highest rearing density.
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    Identification of Host Fish and Experimental Culture of Juveniles for Selected Freshwater Mussel Species in Virginia
    Steg-Geltner, Michelle Birgit (Virginia Tech, 1998-06-20)
    Host fishes for the state-endangered Tennessee heelsplitter (Lasmigona holstonia) and state-threatened black sandshell (Ligumia recta) were identified through induced infestations of glochidia on potential hosts. Largemouth bass (Micropterus salmoides), yellow perch (Perca flavescens), convict cichlid (Cichlasoma nigrofasciatum), platy (Xiphophorus maculatus), green sunfish (Lepomis cyanellus), rock bass (Ambloplites rupestris), redbreast sunfish (Lepomis auritus), and white perch (Morone americana) were identified as suitable hosts for L. recta. The banded sculpin (Cottus carolinae) and rock bass were identified as hosts for L. holstonia; striped shiner (Luxilus chrysocephalus), central stoneroller (Campostoma anomalum), and warpaint shiner (Luxilus coccogenis) were identified as potential hosts. Additionally, rock bass and bluegill (Lepomis macrochirus) were identified as potential hosts for the state-endangered spectaclecase (Cumberlandia monodonta), with numerous encysted glochidia present at 11 days postinfestation when the fish died. Recirculating culture systems of different design were tested for suitability in juvenile mussel culture. In one system (high maintenance), juveniles of the wavy-rayed lampmussel, Lampsilis fasciola, were kept in culture dishes, and in the other system (low maintenance), the juveniles were kept in culture beds. At the end of the 16-wk culture period, the 31.3% (± 15.4) survival exhibited in the dish culture system was significantly greater than the 3.1% (± 2.8) survival in the bed culture system (P< 0.01, Tukey-Kramer). However, mussels grown in the bed system exhibited significantly greater growth (1.4 ± 0.50 mm height, 1.8 ± 0.76 mm length) than those grown in the dish system (0.86 ± 0.19 mm height, 1.1 ± 0.27 mm length) (P<0.01, Tukey-Kramer). Using the high maintenance dish culture system and juveniles of L. fasciola, the influence of high (4.1%) and low (2.5 %) organic content in substrate, and high (250 mg/L CaCO₃) and low (50 mg/L CaCO₃) water hardness levels were assessed on growth and survival. After 15 wk, juveniles in the high water hardness treatment exhibited significantly greater survival and growth (44.2 ± 9.3% survival, 1.5 ± 0.28 mm height, 2.1 ± 0.41 mm length) than those in the low water hardness treatment (9.0 ± 7.9% survival, 1.3 ± 0.25 mm height, 1.8 ± 0.37 mm length) (P<0.01, Tukey- Kramer). Juveniles in the high organic substrate exhibited similar growth (1.41 ± 0.24 mm height, 1.96 +- 0.37 mm length) to those in the low organic substrate (1.39 ± 0.28 mm height, 1.94 ± 0.42 mm length). Juveniles grown in high hardness and high organic substrate had similar survival (27.4 +- 9.2%) to those in low organic substrate (25.8 ± 8.1 %). For the culture of L. fasciola juveniles, I recommend using a culture system that is cleaned regularly (weekly), receives a consistent (daily) supply of algal food, has relatively even flow, and from which juveniles are easily sampled. I recommend culturing them in relatively hard water (~ 250 mg/L CaCO₃), in a substratum with some organic content. These recommendations may warrant modification for the culture of other freshwater mussel species.
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    An investigation of the effects of ozone in a recirculating aquacultural production system
    Johnson, William P. (Virginia Tech, 1991-05-05)
    The use of ozone in a recirculating aquacultural production system on a commercial scale was investigated. ozonation was responsible for statistically significant differences in all test parameters, including: heterotrophic plate count, total coliforms, fecal coliforms, total solids, and total volatile solids. Results indicated ozone had a significantly positive effect in the recirculating aquacultural production system. Further study is recommended, however, to better understand the effects of ozone and to justify economically the use of ozone in commercial systems.
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    A Low Cost Bar Grader for the Harvest of Hybrid Striped Bass (Morone chrysops x M. saxatilis)
    Easter, C. C.; Helfrich, Louis A.; Tate, A.; Libey, George S. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2002-06-01)
    Four bar graders were designed and built to separate a mixed-size population of market-size reciprocal cross hybrid striped bass Marone chrysops x M. saxatilis in rectangular culture tanks in an indoor, recirculating aquaculture system. Grader frames were constructed of 5.1 cm (2 inch) PVC pipe and fittings. PVC electrical conduit ( 1.27 cm, 0.5 inch) was used to form a series of parallel, equally spaced vertical bars within the frame. Bar slot spaces were 1.90, 2.54, 3.20, or 3.80 cm (0.75, 1.0, 1.25, 1.5 inches). A strip of flexible vinyl siding was attached to the outer edges of the bar grader to permit a tight fit between the grader and tank walls, and prevent fish from swimming around the grader. The graders were placed sequentially into one end of the tank, largest slot size first, and maneuvered to the opposite end. Each grader remained in the tank for 60 min. Fish too large to pass through a grader were netted and measured for weight, length and width. Regression analysis was performed for average weight retained at each bar spacing (Y = 7.13619 + 0.070716 X; r2 = .9987). By rearrangement, an equation was derived which allows a culturist to select a bar spacing that retains fish of a predetermined weight: Grader bar slot size (mm)= Fish weight (g) -177.9 / 31.7). Construction of each grader required approximately 2 h, and materials cost $20.