VTechWorks Repository :: Browsing by Author "McLean, Ewen W."

Browsing by Author "McLean, Ewen W."

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Chemical, Physical and Sensorial Compositions of Farmed and Wild Yellow Perch (Perca flavescens), Southern Flounder (Paralichthys lethostigma) and Coho Salmon (Oncorhynchus kisutch)
Gonzalez Artola, Sonia (Virginia Tech, 2004-11-30)
This study compared chemical, physical and sensorial properties of wild and farmed fish. Farmed yellow perch fillets showed higher lipid contents (2.78% vs. 1.39%); softer texture (0.41 J/g vs. 0.53 J/g); whiter color (higher L* and lower b* values); different fatty acid profile (higher n-3/n-6 ratio), and mineral composition, when compared to their wild counterparts. Similar amino acid profiles and flavor were found between treatments. Dietary protein by itself influenced color and flavor of yellow perch fillets. Yellow perch fed the highest protein concentrations exhibited higher b* (yellow) values and overall flavor was significantly different (p ≤ 0.05) between fish fed a 45% and 55% crude protein (CP) diet. A 12-week feeding trial determined that southern flounder protein requirement to achieve maximum weight was around 50% CP. Farmed southern flounder were found to be higher in lipid content (3.04 % vs. 1.61%), softer (0.24 J/g vs. 0/33 J/g), different in color (lower a* [green to red]), mineral, fatty acid composition (higher n-3/n-6 ratio) and flavor, than wild. The effect of a crab meal-supplemented diet, on flavor and body composition of flounder was analyzed. The inclusion of crab meal as a flavor enhancer affected the flavor and also influenced color of the fillets (lower L* [lightness] and higher b* values). Wild, farmed and growth-enhanced transgenic coho salmon (market-size) were compared, regarding their body composition and nutritional value. All treatments showed highest lipid levels in the ventral frontal sections and lowest in the tail (p ≤ 0.05). Overall wild fish showed lower lipid levels and firmer values in the tail sections (p ≤ 0.05). The insertion of the growth hormone gene affected lipid deposition, texture and color, since transgenic fish showed firmer texture than farmed and similar lipid contents even when fed a high-energy diet. L*, a* and b* values were similar for wild and transgenic coho in most of the body zones. Fillet mineral and amino acid profiles were similar across all groups. No differences were observed in flavor between farmed and wild coho, while panelists preferred the appearance of farmed, when compared to transgenic coho.
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.
Development of a suitable diet for endangered juvenile oyster mussels, Epioblasma capsaeformis (Bivalvia:Unionidae), reared in a captive environment
Vincie, Meghann Elizabeth (Virginia Tech, 2008-08-25)
Epioblasma capsaeformis, commonly named the oyster mussel, once occupied thousands of miles of stream reaches, but has now been reduced in range to small, isolated populations in a few river reaches. Due to this significant decline in population numbers, a study was conducted to develop a diet for propagating this endangered species under captive conditions. Oyster mussel juveniles were collected from several sites on the Clinch River and sacrificed for gut content and biochemical composition analyses in summer. Feces and pseudofeces from live river-collected juveniles were examined seasonally for algae, detritus, and bacteria to qualitatively determine diet of specimens. Two feeding trials also were conducted in this study to evaluate effect of diet (commercial and non-commercial diets), on growth and survival of oyster mussel juveniles. From examination of gut contents, fecal and pseudofecal samples, it was apparent that algae and a significant amount of detritus (~90%) composed wild juvenile diets. E. capsaeformis juveniles (1-3 y of age) could have fed on particles up to 20 µm in size and seemed they were mostly ingesting particles within the 1.5-12 µm size range. Protein content of sacrificed juveniles ranged from 313 to 884 mg/g and was highly variable. Glycogen content ranged from 49-171 mg/g. Caloric content of four juveniles ranged from 2,935.10 to 4,287.94 cal/g, providing a preliminary baseline range for future energetic studies on freshwater mussels. Growth was significantly higher in those juveniles fed the triple concentration algae-mix (62,076 cells/ml) than all other diets tested in trial 1. Results of both feeding trials indicated that survival of juvenile oyster mussels was enhanced when fed an algal diet supplemented by bioflocs.
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.
Enhancing Aquaculture Sustainability Through Water Reuse and Biological Treatment
Kuhn, David Dwight (Virginia Tech, 2008-03-28)
Overfishing of natural fisheries is a global issue that is becoming more urgent as the human population increases exponentially. According to the Food and Agriculture Organization of the United Nations, over 70% of the world's seafood species are fully exploited or depleted. This high demand for seafood protein is not going away; and, in fact, an astonishing one out of five people in this world depend on this source of protein. Traditional aquaculture practices use pond and flow-through systems which are often responsible for discharging pollutants into the environment. Furthermore, aquacultural feeds often contain high levels of fish protein, so the demand on wild fisheries is not completely eased. Even though traditional aquaculture has these drawbacks, there is a significant movement towards more sustainable practices. For example, implementing recirculating aquaculture systems (RAS) maximizes the reuse of culture water which decreases water demand and minimizes the levels of pollutants being discharged to the environment. And, alternative proteins (e.g., soy bean) are replacing the fish and seafood proteins in aquaculture diets. Accordingly, the research described in this dissertation focused on maximizing the reuse of freshwater fish effluent to culture marine shrimp. More specifically, by using suspended-growth biological reactors to treat a tilapia effluent waste stream and to generate microbial flocs that could be used to support shrimp culture. This RAS technology will decrease water consumption by increasing the amount of recycled water and will also improve effluent water quality. The biomass generated in the bioreactors could be used to feed shrimp with an alternative source of protein. Treating fish effluent to be reused to culture shrimp while producing this alternative feed, could significantly decrease operational costs and make these operations more sustainable. Understanding which ions are critical for the survival and normal growth of marine shrimp in freshwater effluents is essential. It is also very important to understand how to convert an effluent's organic matter into food for shrimp. Results from studies revealed that the marine shrimp, Litopenaeus vannamei, can be raised in freshwater effluent when supplemented with specific ions and wet microbial flocs fed directly to shrimp can enhance growth in shrimp fed a restricted ration of commercial feed. The treatability of the tilapia effluent using suspended-growth, biological reactors and nutritional analysis of the generated biomass were also reported. Carbon supplementation enhanced reactor performance and microbial floc generation. These microbial flocs also proved to be a superior feed ingredient when dried and incorporated into a pellet feed.
Evaluation of organically certifiable alternate protein sources for production of the marine carnivore, cobia (Rachycentron canadum)
Lunger, Angela Nicole (Virginia Tech, 2006-09-08)
Cobia represents one of the most attractive candidate species for aquaculture in the history of the industry. With rapid growth rate, high survival rates, and delectable flesh, cobia possess highly desirable characteristics for a cultured fish. Although interest in this species is high, issues pertaining to nutritional requirements must be resolved if this animal is to be produced sustainably. Cobia are high level marine carnivores and, as such, require relatively high dietary protein levels which usually are met through the use of fish meal. Fish meal supplies have become limited and costly, and alternate proteins must be utilized if future aquaculture production is to meet demand. Moreover, the movement towards organic aquaculture production presents additional challenges with respect to fish meal inclusion in aquafeeds designed for cobia. This thesis summarizes research pertaining to fish meal replacement in cobia aquafeeds with organically certifiable alternate protein sources. Initial trials with an organically certifiable yeast-based protein source indicated that up to 25% of the fish meal could be replaced without detrimental impacts to growth rates, feed efficiency, or biological indices. Substitution levels above this resulted in decreased performance in all measured parameters. Based on these results and other research however, it is hypothesized that fish meal replacement levels could be increased to 40% without detrimental impacts upon production characteristics. In a subsequent study, multiple organically certifiable alternate protein sources were investigated for their ability to replace fish meal in aquafeeds for juvenile cobia. A 25% inclusion level of yeast-based protein was used along with a 40% inclusion level. The remaining alternate proteins (soybean meal, soybean isolate, and hemp) also were included at 40% of dietary protein. Two additional diets were formulated to contain all four alternate proteins with or without 8% fish meal. Lack of fish meal resulted in poor survival, while the 8% inclusion of fish meal resulted in decreased overall performance compared to fish fed the fish meal control and the diets with up to 40% organic protein source. When included at 40% of fish meal replacement, these alternate protein sources led to returned excellent weight gain, feed efficiencies, and other production characteristics when compared to the 100% fish meal control diet. I hypothesized that higher inclusion level of alternate protein sources could be achieved with specific amino acid supplementation. Two additional trials involved the use of the yeast-based protein with supplementation by the amino acids methionine, tryptophan, and taurine. Diets containing 50 and 75% of the yeast-based protein were investigated with the addition of methionine (0.3%) and tryptophan (0.2%), with and without taurine (0.5%). Taurine significantly and dramatically increased production performance. A final trial re-evaluated that ability of the yeast-based protein to completely replace fish meal with supplemental taurine (0.5%). While growth at the 50% inclusion level equaled that of the control, at higher levels (75 and 100%), growth was reduced even with taurine supplementation, leading to the hypothesis that other essential amino acids may also have been limiting. This thesis presents evidence that replacement of fish meal, as well as organic production of cobia, is feasible. However, these studies also illustrate the necessity of developing quantitative amino acid requirement data for cobia if these goals are to be fully realized.
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.
An Evaluation of Relative Weight as an Indicator of Body Composition and Nutritional Status in Wild Fish
Copeland, Timothy (Virginia Tech, 2004-11-02)
Condition indices are widely used to generate biological insight. However, purported relationships to indices are imprecise or inconsistent in the wild. I investigated factors influencing relative weight (Wr), a condition index commonly applied to fish. I first examined the relationship of Wr to physiology in two bluegill Lepomis macrochirus populations over a year. I regressed tissue composition (percentages of lipid, protein and water) and organ indices (liver-, gonad-, and viscerosomatic indices) on Wr. The regression model had little explanatory power (adjusted R2 = 0.14). Lipid was most influential (partial R2 = 0.11), but correlation strength fluctuated by season and population. To test the generality of these results, I performed a similar regression on a bluegill population with higher average Wr. Again, variables were not well correlated to Wr (adjusted R2 = 0.13). Combining comparable data sets increased Wr range 64% but explanatory power was low (adjusted R2 = 0.41) Both studies showed that expected correlations of physiological variables to Wr can be confounded in natural environments. To examine differences between natural and laboratory environments, I manipulated initial Wr and ration of juvenile bluegills. Although organ indices and tissue composition of all groups changed in time ((Wilks' Δ > 0.387, P > 0.03), no temporal pattern matched to Wr. At termination, all variables showed high correlations to Wr (r2 > 0.64). Correlation strength increased with time in the laboratory. Both ration and environment influenced correlations. Lastly, I examined differences in interpretation of Wr for chain pickerels Esox niger, largemouth bass Micropterus salmoides, and black crappies Pomoxis nigromaculatus. Regression models were compared to concurrent bluegill models. Piscivore models fit well (adjusted R2 > 0.50), whereas bluegill models had the lowest explanatory power (adjusted R2 = 0.13 and 0.14). Ecological specialization affected correlations to Wr. Theoretically, condition index values are determined by resource acquisition versus expenditure. Exact physiological expression is determined by life history and performance. Condition indices are imprecise predictors but track net somatic investment with great generality. Ancillary data, such as growth or length-at-maturity, may clarify interpretation. Condition indices should be used as qualitative monitoring tools, not omnibus physiological predictors.
An Evaluation of the Survival and Growth of Juvenile and Adult Freshwater Mussels at the Aquatic Wildlife Conservation Center (AWCC), Marion, Virginia
Liberty, Aaron Jason (Virginia Tech, 2004-12-09)
The decline of many freshwater mussel populations in the United States has brought about the need for facilities in which mussels can be held for purposes of relocation, research, and propagation. The Aquatic Wildlife Conservation Center (AWCC) of the Virginia Department of Game and Inland Fisheries (VDGIF) serves as a freshwater mussel conservation facility in southwest Virginia. The goals of this study were: (1) to determine whether adult freshwater mussels could maintain energy reserves at AWCC (2) to determine whether adults could produce mature gametes at AWCC and (3) to establish suitable rearing conditions for juvenile mussels at the AWCC. In fall 2002, four species of mussels, Villosa iris, V. vanuxemensis, Amblema plicata, and Pleurobema oviforme, served as surrogates for endangered species and were relocated to the AWCC. Three energy reserves (glycogen, protein, and lipid) were measured seasonally (fall 2002 to summer 2004) from mantle tissue and compared between AWCC specimens and those from their wild source populations. The gametogenic stage of each species was also compared to determine whether gametogenesis was occurring in captivity. In summer 2003, the first of two juvenile experiments tested the effects of three rates of water flow (1 L/min, 3 L/min, and 7 L/min) on the survival and growth of V. iris and Epioblasma capsaeformis reared in flow-through troughs. In summer 2004, round flow-through tanks were used to assess the effects of three sizes of substrate (fine sediment, fine sand, and coarse sand) and sampling frequency on the survival and growth of V. iris. Gut content analyses also were conducted at the end of each experiment to determine which algal species were being consumed. Overall survival rates were as follows: A. plicata, 100 %; V. vanuxemensis, 86 %; V. iris, 79 %; P. oviforme (2002 collection), 53 %; and P. oviforme (2003 collection), 50 %. All energy reserves varied among seasons, but every species except P. oviforme (2003 collection) had levels higher than those in source populations at the end of this experiment. Glycogen appeared to be the best indicator of condition in these species, with protein also being important in the 2003 collection of P. oviforme. Mature gametes were found in all four captive species in 2003 and 2004, with lipids appearing to fuel gametogenesis. Additionally, gametogenesis was occurring earlier in captive long-term brooders than in the wild, possibly due to warmer water temperatures at AWCC. The first juvenile experiment resulted in 15 % overall survival, with 1 L/min having the greatest survival (18 %), and the 3 L/min having the greatest growth (656 Î¼m). In the second experiment, dishes left unsampled had significantly greater survival (40 %) (P<0.05) of juveniles than those which were sampled (27 %). The unsampled fine sand treatment had significantly greater survival than the other two unsampled treatments (52 %) (P<0.001). Sampled juveniles in fine sediment had the greatest growth (887 Î¼m). Also, juveniles from Experiment 1 were consuming primarily Navicula, with Coelastrum and Chlorella consumed in greatest abundance in Experiment 2. Results indicate that most adult mussels maintained energy reserves and produced mature gametes, and that juveniles of V. iris had good survival and growth. Only P. oviforme had survival rates lower than expected and did not appear to maintain condition at AWCC. Based on results of the species tested, environmental conditions at AWCC appear suitable for the survival of most adult and juvenile freshwater mussels.
Factors affecting largemouth bass recruitment in a trophy bass reservoir of Virginia, Briery Creek Lake
Ray, Bradley A. (Virginia Tech, 2008-07-28)
Briery Creek Lake (BCL) has low abundance of young largemouth bass (LMB) compared to Sandy River Reservoir (SRR), which could jeopardize the trophy-LMB management goal in BCL. I assessed factors that may limit recruitment of LMB in BCL: angling, predation, competition, growth, and food availability. Age-0 LMB were monitored from nesting through their first summer with nest surveys, light traps, and electrofishing. Nesting success was higher in BCL (53%) than SRR (31%). Initial light trap catch-per-unit-effort (CPUE) was higher in BCL than SRR but, by July, light trap and electrofishing CPUE was higher in SRR than BCL. LMB nest success, growth, and CPUE did not differ between areas in BCL that were experimentally closed and areas left open to angling. Predation on age-0 LMB did occur in BCL, but was not higher than predation in SRR. Diet overlap between age-0 LMB and bluegill in BCL was >60% during June, indicating potential for competition. Zooplankton samples indicated that density of copepods was similar between reservoirs (2.3/liter); however, the average size of copepods was smaller in BCL (0.42 mm) than SRR (0.71 mm). I examined the activity of trypsin, which digests and converts protein. Trypsin activity was lower in BCL than SRR on 23 and 27 June, indicating that a nutritional deficiency exists for age-0 LMB in BCL. This deficiency was likely caused by the reduced zooplankton size in BCL and led to slower growth of age-0 LMB during June in BCL (0.8 mm/day) than SRR (1.2 mm/day). The fact that age-0 LMB CPUE in BCL dropped lower than SRR by July, despite BCL having a greater nesting success and higher CPUE in early June, indicates that a recruitment bottleneck for LMB occurred in June. Maintaining the trophy LMB fishery in BCL requires management options that consider the factors in June that affect recruitment. I recommend decreasing the presently overabundant aquatic macrophytes in BCL, thus allowing for increased nutrient availability for phytoplankton, the primary food source of zooplankton. This could increase the density and size structure of zooplankton, and thereby increase food availability for age-0 LMB.
A Holistic Approach to Taxonomic Evaluation of Two Closely Related Endangered Freshwater Mussel Species, the Oyster Mussel (Epioblasma capsaeformis) and Tan Riffleshell (Epioblasma florentina walkeri) (Bivalvia: Unionidae)
Jones, Jess W. (Virginia Tech, 2004-03-19)
Primers for 10 polymorphic DNA microsatellite loci were developed and characterized for the endangered oyster mussel Epioblasma capsaeformis from the Clinch River, TN. Microsatellite loci also were amplified for individuals collected from the following additional populations or species: (1) E. capsaeformis from Duck River, TN; (2) E. florentina walkeri from Indian Creek, upper Clinch River, VA; (3) E. florentina walkeri from Big South Fork Cumberland River, TN; and (4) E. torulosa rangiana from Allegheny River, PA. Allelic diversity ranged from 9-20 alleles/locus, and averaged 13.6/locus for all 5 populations investigated. Average expected heterozygosity (HE) per locus ranged from 0.78-0.92, and averaged 0.86. A genetic characterization of extant populations of E. capsaeformis and E. florentina walkeri was conducted to assess taxonomic validity and to resolve conservation issues related to recovery planning. These mussel species exhibit pronounced phenotypic variation, and are difficult to characterize phylogenetically using DNA sequences. Monophyletic lineages, congruent with phenotypic variation among species, were obtained only after extensive analysis of combined mitochondrial (1378 bp of 16S, cytochrome-b, ND1) and nuclear (515 bp of ITS-1) DNA sequences. In contrast, analysis of variation at 10 hyper variable DNA microsatellite loci showed moderate to highly divergent populations based on FST values, which ranged from 0.12-0.39. Quantitative genetic variation was observed in fish host specificity, with transformation success of glochidia of E. capsaeformis significantly greater (p<0.05) on the greenside darter Etheostoma blennioides, and that of E. f. walkeri significantly greater (p<0.05) on the fantail darter E. flabellare. Lengths of glochidia differed significantly (p<0.001) between species, with sizes ranging from 241-272 μm. Underwater photographs of mantle-pads and micro-lures of female mussels documented fixed phenotypic variation between species. The texture and color of the mantle-pad of E. capsaeformis is smooth and bluish-white, while that of E. f. walkeri is pustuled and brown, with tan mottling. Based on extensive molecular, morphological, and life history data, a population of E. capsaeformis from the Duck River, TN is described and proposed as a separate species, and a population of E. f. walkeri from the upper Clinch River, VA is described and proposed as a separate subspecies. Genetic management guidelines were developed to assess taxonomic status, genetic variation of donor-recipient populations targeted for augmentation, and field and laboratory protocols to maximize genetically effective population size, minimize genetic changes in captive-reared progeny, and prevent the release of juvenile mussels into non-native drainages. A pragmatic approach to species recovery is advocated; one that incorporates the principles of conservation genetics into breeding programs, but prioritizes the immediate demographic needs of critically endangered mussel species.
Nutritional control of gene expression, larval development and physiology in fish
Salze, Guillaume Pierre (Virginia Tech, 2008-09-12)
During preliminary research on cobia (Rachycentron canadum, L.) it became increasingly clear that more in-depth information was required to provide enabling techniques for the cobia aquaculture industry to develop more rapidly. A unifying theme in many of the more important issues facing cobia aquaculture is nutrition. This led to nutritional investigations with larval and juvenile fish highlighting the impacts of dietary ingredients on animal performance. Indeed, nutrition can be viewed as a central lever of action through which many aspects of the physiology and the environmental (water) quality of the animal can be controlled. The first project focused on studying the larval development of cobia, a fish species highly suitable for aquaculture for which the industry is nascent. I described the time-course of development of external sensory organs, gut morphology and relevant digestive enzymes under controlled conditions using electron microscopy, histology and spectrophotometric assays. The developmental sequence of larval cobia could be separated in two phases, with a transition period between 12 and 14 days post hatch (dph). This transition is characterized by the formation of the intestinal loop, the establishment of basic cranial neuromast configuration, leading to the initiation of the onset of pancreatic enzymes and the increase of growth rate. In addition, the effects of dietary taurine supplementation and incorporation of mannan oligosaccharides (MOS) into live feeds on cobia larvae development was examined. Fish fed supplementary MOS did not grow faster but displayed higher microvilli length and density. In addition, MOS-fed fish were more resistant to salinity stress. The dietary supplementation of taurine resulted in a dramatic increase in survival, growth and development rates, and enzymatic activities. The second project aimed at refining cobia juvenile nutrition, assessing fish meal and fish oil replacements. Novel sources, including soy protein and oil, were investigated with and without amino acid and MOS supplementations, yielding promising results. Indeed, both fish meal and fish oil were replaced completely and successfully in feeds for juvenile cobia. In addition, novel ingredients (e.g. marine algae meals and soy protein concentrate) were identified to effectively achieve such replacement. The third and last project dealt with nutrient-gene interactions, specifically centering attention on immunostimulants for which the underlying mechanisms of action remain poorly characterized. Here, dietary MOS, nucleotides and selenomethionine (Se-met) were offered to zebrafish whose transcriptome was analyzed by microarray. The immune system, humoral or cellular, innate or adaptive, exhibited different patterns of response according to the immunostimulating nutrient used. In addition, various genes involved in cell cycle and cytokinesis were concomitantly expressed. An intriguing observation related to the insulinomimetic effect of Se-met. In other words, Se-met impacted pathways normally regulated by insulin, such as the MAPK and PI3K pathways. Some Insulin-like Growth Factors (IGF) and IGF bindgin proteins were up-regulated. Additional research is however necessary prior to advocating for the use of these additives, in order to further investigate their respective pros and cons.
Risk Analysis of Tilapia Recirculating Aquaculture Systems: A Monte Carlo Simulation Approach
Kodra, Bledar (Virginia Tech, 2007-04-06)
The purpose of this study is to modify an existing static analytical model developed for a Re-circulating Aquaculture Systems through incorporation of risk considerations to evaluate the economic viability of the system. In addition the objective of this analysis is to provide a well documented risk based analytical system so that individuals (investors/lenders) can use it to tailor the analysis to their own investment decisions—that is to collect the input data, run the model, and interpret the results. The Aquaculture Economic Cost Model (AECM) was developed by Dr. Charles Coale, Jr. and others from the department of Agricultural and Applied Economics at Virginia Tech. The AECM is a spreadsheet model that was developed to help re-circulating aquaculture producers make strategic business decisions. The model can be used by potential producers interested in investing in re-circulating aquaculture through development of a financial analysis that in turn will help them obtain funding for the enterprise. The model is also useful for current producers who want to isolate inefficient aspects of their operation. AECM model consists of three major sections which include the Data Entry, Calculations and Analysis. The first section requires that the producer conducts background research about their operation to ensure accurate calculation and analysis. The calculation section provides a great deal of information about the operation's finances, while the analysis section provides information about the operation's financial stability. While the AECM is a powerful model, it is based on single, usually mean, values for prices, costs, and input and output quantities. However, market, financial and production uncertainties result in fluctuating prices, costs and yields. An individual who is making management decisions for a re-circulating aquaculture system will be faced with some or all of these uncertainties. By adding simulation to the AECM model to account for these uncertainties individuals will be able to make better management decisions. Information of the varying likelihoods or probabilities of achieving profits will be of crucial interest to individuals who plan on entering into or modifying an existing aquaculture system. Risks associated with six variables were examined in this paper: feed cost, feed conversion, mortality rate, capital interest rate, final weight, and output price. Data for the Interest Rate and output price were obtained from the Federal Reserve System and NMFS website respectively. Expert opinion was the source of data for the other variables. After probability distributions were applied to the random variables to account for the uncertainty the model was simulated for ten thousand iterations to obtain expected returns for three years in advance that the model calculates an income statement. In addition to that, sensitivity analyses were carried out in order to inform the producer which factors are contributing the most to the profitability of the operation. In this way the producer will have a better idea as to which aspects of the operation to monitor closely and consider modifying. The analysis shows that the mean income for the three years will be negative and thus the business would be losing money. The simulated mean net incomes were: -$216,905, -$53,689, -$53,111 for year1 through year3 respectively. Sensitivity analysis confirmed that output price is by far the most significant input that makes the overall bottom line to fluctuate most. Output price was on top of the list for all the three years analyzed in this study. Feed cost and Feed conversion were the next most significant inputs. The other inputs were also significant in explaining the fluctuation of the bottom line; however both their regression and correlation coefficients were small.
Treatment of Wet Fish Sludge with Vermicomposting
Mishra, Sudhanshu (Virginia Tech, 2003-08-29)
Aquaculture, the cultured production of fish, is growing at a rapid pace worldwide. The industry is generating approximately 140,000 cubic meter wastewater per year. For this industry to flourish, viable methods for treating the resulting waste stream must be identified. The various methods were tried by many researchers like sand filtration method, recirculating aquaculture system, intermittent filtration methods. The most of the industries use sand filtration methods for treating aquaculture wastewater and the problems associated: the reduction in hydraulic conductivity, accumulation of solid due to which anaerobic conditions developed. This study investigated possible treatment technologies for wastewater and sludge produced from Blue Ridge Aquaculture (BRA), an indoor, recirculating aquaculture facility where tilapias (Oreochromis) are raised. Research focused on the use of vermicomposting in conjunction with sand bed filtration to filter aquaculture waste and treat the resulting solids. Two experiments were conducted: a feedstock acceptability test and a filter bed test. The feedstock acceptability test evaluated the suitability of the fish sludge (mixed with cardboard) as a feedstock for the worms involved in the vermicomposting process. The results showed that as the percentage of fish sludge in the feed increased from 0 to 50%, there was a corresponding increase in the growth rate of E.fetida biomass. The filter bed test appraised the feasibility and effectiveness of incorporating vermicomposting in sand filter beds to directly treat aquaculture wastewater. Popular in early wastewater treatment systems, sand filtration has seen a resurgence in recent years. To test the potential for even more effective filtration, sixteen sand filter beds were established--twelve that included worms and four that did not. Wastewater (1.5 % total solids) from BRA was applied to the sand beds at loading rates of 400 to 1000 grams of volatile solids/m2/week. Filter beds containing worms exhibited no ponding over the 70-day experimental period. However, all units without worms failed (exhibited ponding) by the 24th day of operation. Removal efficiencies obtained from the filter bed study for total solids (TS), volatile solids (VS), total suspended solids (TSS), chemical oxygen demand (COD), total phosphorus (TP), sulfate, chlorides, and ammonia-N were greater in filter beds with worms than beds without worms. The worms were crucial to maintaining porosity in the filter beds, hence keeping the filters functioning over time. Worm filter beds removed approximately 100% of the TS, VS, TSS and Ammonia-N, 90% of the TP, 50% of the chlorides, 80% of the sulfate and 70% of the COD. Maximum hydraulic conductivity of 35 cm/day was achieved at the maximum application rate. All the worm filter beds therefore had greater hydraulic conductivity than filter beds without worms. The potential impact is to treat the wastewater effectively, to increase the flow of water, and may be to maintain the aerobic conditions on the worm filterbeds.
The use of bioelectrical impedance analysis for estimating the body composition of various fish species
Duncan, Michael Bennett (Virginia Tech, 2008-04-25)
The reliable measurement of growth and condition is vital for effective fisheries assessments. Biologists have long attempted to estimate condition for their assessments, but a reliable method to nonlethally estimate body composition is lacking. Proximate analysis is the most dependable and accurate method for estimating internal composition, but it is lethal, time consuming, and expensive. Recent research has shown bioelectrical impedance analysis (BIA) to be an effective method for estimating proximate composition in some fishes. The technique is quick, inexpensive, and, most importantly, nonlethal, which is vital when examining endangered species or cultured fish. My research focused on developing BIA indices for several new species of fish, using those indices to evaluate the body composition of fish in the field, and determining whether water temperature influenced resistance and reactance measurements. I found that BIA accurately estimated the body composition of bluegill Lepomis macrochirus, redear sunfish Lepomis microlophus, brook trout Salvelinus fontinalis, and northern logperch Percina caprodes (r2 ≥ 0.71, p < 0.0001). I also determined that bluegill and redear regressions were not significantly different (P ≥ 0.10) suggesting they can be used interchangeably during future studies. Laboratory studies revealed that water temperature did not significantly influence resistance and reactance measurements of bluegill, redear, and largemouth bass Micropterus salmoides (P ≥ 0.18). These results, along with previous literature, indicate that BIA may be an accurate and reliable assessment tool for fisheries biologists.
Using computer simulation to reduce costs at a recirculating aquaculture facility
Simon, John (Virginia Tech, 2005-04-26)
The Recirculating Aquaculture System can be considered as a dynamic system in which the system variables change instantaneously during the growing period. This effort uses a combination of discrete and continuous simulation to model this system. Changing the values of a certain set of variables (regressors) result in changes to another set of variables (responses). So the inter relationship between the regressors and responses are first defined. Then the changes to the regressors are defined as a function of time. The computer program then simulates time from the beginning to the end of the growing period. By attaching cost factors, the cost of running the system during the growing period can be obtained. In a real facility, some of the regressors can be changed by the operator, affecting the overall cost. So, in this model, different values for this subset of regressors are tried out using a proprietary heuristic called "Optquest" to arrive at a low cost configuration. Some of the responses are also constrained while trying to minimize the cost, e.g., ammonia level. The output of the model gives a cost savings of about $10,000 over a period of 8 months for a facility with 12 tanks by suggesting optimal values for the water replenishment rate, water recirculation rate, oxygen supply rate and feeds per day.

Browsing by Author "McLean, Ewen W."

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