Browsing by Author "Craig, Steven R."

Now showing 1 - 20 of 21
  • Thumbnail Image
    An Assessment of Suitable Feed Quantity and Quality for Riffleshell Mussels (Epioblasma spp.) Held in Captivity
    Bush, Amy L. (Virginia Tech, 2008-01-30)
    Optimum feed ration was determined for riffleshell mussels (Epioblasma spp.) held in captivity. Mussels were fed one of four rations (0.49, 0.72, 1.28, or 1.73 mg dry wt/l) of algae Neochloris oleoabundans for 2-h trials in spring, summer, fall, and winter. The test ration resulting in the most feed absorbed per hour (net absorption rate, mg/h) was determined to be the optimum feed ration. Mussels absorbed the greatest amount of food when fed the highest ration. Suggested feed rations for captive adult Epioblasma species are 1.73 mg/l when held at moderate temperatures (i.e., 15-19C), and 1.28 mg/l when held at cool temperatures (i.e., near 11C). Seasonal utilization of protein by oyster mussel (E. capsaeformis) and rainbow mussel (V. iris) was examined with O:N ratios. Ratios were determined for mussels fed a low or high-protein diet (0.11, or 0.31 mg protein/mg dry algal feed), and for mussels held in a hatchery or in the Clinch River, in spring, summer, and winter. Significant differences in O:N ratios were not observed between mussels fed a low or high-protein diet (p > 0.05). The O:N ratios were significantly highest in spring and summer, and lowest in winter (p < 0.05). Mussels primarily utilized protein in spring and summer, and conserved protein in winter. A diet high in energy was suggested in spring and summer, and a diet high in protein was suggested in winter.
  • Thumbnail Image
    Biology, Captive Propagation, and Feasibility of Pearl Culture in the Pink Heelsplitter (Potamilus Alatus) (Say, 1817) (Bivalvia: Unionidae)
    Hua, Dan (Virginia Tech, 2005-08-15)
    Pink heelsplitter (Potamilus alatus) mussels collected from Kentucky Lake, TN were held at two bottom locations (0.6 m, 2.5 m) and suspended in pocket nets (at depth about 1.0 - 1.5 m) in a pond at the Freshwater Mollusk Conservation Center (FMCC), Virginia Tech, for 1 yr. Survival of mussels after 1 yr was significantly different, with poorest survival (30 %) in the bottom of the deep end; and no difference between the shallow end (83.3 %) and the suspended pocket nets (63.3 %). Survival of mussels was inversely related to water temperature (r = - 0.72); lowest monthly survival occurred in summer, resulting in a significant difference among the three locations with a similar trend after 1 yr. The glycogen reserves of mussels in captivity for 1 yr differed by pond location, higher in mussels at the shallow end than those in suspended pocket nets and at the deep end. Therefore, the shallow end of pond was more suitable for holding mussels long-term, while the suspended pocket nets are an alternative site for holding captive mussels. Additionally, dissolved oxygen was very low at the deep end (1.9 mg/L) in summer, while it was adequate (range from 5.7 - 6.4 mg/L) at the location of suspended pocket nets, and 5.0 mg/L at the shallow end (24.7 °C). Data for 40 specimens indicated that sexual dimorphism in valve shape occurred in P. alatus. Female mussels had a significantly (p < 0.0001) greater ratio of height (H) to length (L) (52.3 %) and width (W) to length (31.8 %) than males (H/L: 48.4 %; W/L: 28.8 %), respectively. The posterior ends were somewhat round to oval in males and bluntly squared or truncated in females. Female mussels were more inflated than males. These morphological differences can be used to distinguish females from males during field collections. The red drum (Sciaenops ocellatus) was identified as a new fish host for P. alatus, as 48 active juveniles were transformed by this species, which is not a natural host. Four glochidia were observed on the fins versus 2,307 on the gills of five red drum. Freshwater drum also was verified as a suitable host fish, but black crappie (Pomoxis nigromaculatus), banded sculpin (Cottus carolinae), yellow perch (Perca flavescens) and nile tilapia (Oreochromis nilotica) did not support transformation of glochidia to juveniles. Survival and growth of propagated juveniles of P. alatus were assessed regarding the effects of algal diets (Nannochloropsis oculata and Neochloris oleoabundans) and substrate type (fine sediment and sand). Overall, survival of juveniles after 17 d ranged from 23.8 to 66.8 %, with mean of 48.5 %; however, survival dramatically declined during the next 2 wk period to only 5.8 % (range of 1.8 to 7.8 %). Survival rate of juveniles was significantly different (p = 0.027) between substrates, but not in diets (p = 0.520), with the lowest survival rate of 23.8 % in sand substrate and fed N. oculata. Juveniles grew faster in fine sediment (23.0 % increase in shell length) than in sand substrates (10.5 % increase) (p = 0.002). Moreover, mean growth rate of juveniles was 4.9 μm/d during the first 2 wk, but decreased to 0.2 μm/d in the remaining 2 wk. Therefore, fine sediments seemed more appropriate for juvenile culture compared to sands. Both species of algae, N. oculata and N. oleoabundans, can be used to feed juveniles in the laboratory. Adult pink heelsplitters were used to study feasibility of pearl production by using two surgical implants (non-nucleated implant = NNI, and image pearl implant = IPI) in two ponds of different nutrient levels (FMCC pond and Duck pond). NNI and IPI pearls with purple or purplish luster were successfully produced in P. alatus. Pearl weight was not significantly different (p = 0.562) between two ponds. No differences in monthly survival rates of mussels were observed in either pond (p = 0.051), or among mussels with surgical implants and the no-surgery control mussels (p = 0.881). Consequently, P. alatus can be considered a potential species for producing purple pearls in pearl culture. Additionally, mussels in the Duck pond had higher (p < 0.0001) glycogen levels, similar to those in wild collected mussels, than those in the FMCC pond, indicating that this pond environment may be more suited for holding implanted mussels in captivity.
  • Thumbnail Image
    Book Review: Food Intake in Fish
    Craig, Steven R. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2001-06-01)
    As the field of fish nutrition continues to grow and flourish, current reference texts updated with the latest and most relevant references are becoming more important and necessary. Food Intake in Fish, edited by Dominic Houlihan, Thierry Boujard and Malcolm Jobling is an excellent addition to the library of anyone involved in the culture of, or experimentation with fish...
  • Thumbnail Image
    Characterization of Suitable Habitats for Freshwater Mussels in the Clinch River, Virginia and Tennessee
    Ostby, Brett John Kaste (Virginia Tech, 2005-03-08)
    With a new focus on flow regulation by the Tennessee Valley Authority (TVA) in reservoir tailwaters, it is now possible to recover many mussel species that once occurred in these reaches. Before flows can be modified to create habitat for freshwater mussels, suitable microhabitat conditions must be defined. In this study, I used multiple approaches to define suitable microhabitats for species in the free-flowing upper Clinch River, Virginia and Tennessee, where reproducing mussel populations persist. During summer low flows in 2003 and 2004, I measured flow and substrate conditions in over 1000 microhabitat patches (0.25 m² quadrat samples) across five river reaches. Flow characteristics and embeddedness were significantly different between microhabitats occupied and unoccupied by the most abundant species (MRPP, p < 0.05). Comparison of simple and multiple logistic regression models with Akaike's Information Criteria (AIC) demonstrated that increasing Fleisswasserstammtisch (FST) hemisphere number (a measure of shear stress), decreasing degree of embeddedness, and increasing mean column velocity best explained species occurrences in a microhabitat patch. Subtle differentiation in habitat use among species was observed; however, most species appeared to be microhabitat generalists. Species were grouped into three habitat guilds using corresponding canonical analysis and cluster analysis: fast-flow specialists (FFS), fast-flow generalists (FFG), and slow-flow tolerant (SFT). I used the same data set to develop and test transferability of Habitat Suitability Criteria (HSC) for three habitat guilds and seven species of adult freshwater mussels. Nonparametric tolerance limits were used to define the range of suitable and optimal habitat during summer low flows. Optimal habitat was defined as those ranges of FST hemisphere number, mean column velocity, and embeddedness occupied by the central 50% of independent observations for a species or guild, whereas suitable habitat was defined by those ranges occupied by the central 90% of observations. The transferability of criteria to other reaches of the Clinch River was assessed using one-sided Chi-square tests. Criteria developed for the fast-flow specialist (FFS) and fast-flow generalist (FFG) guilds, as well as most criteria for species in those guilds, transferred to destination reaches. In contrast, criteria developed for the slow-flow tolerant (SFT) guild and individual constituent species consistently failed to transfer. Criteria for FFS and FFG guilds and their constituent species should be incorporated into flow simulation models such as PHABSIM to gauge the effect of minimum flows on mussel habitat quality and quantity. These criteria could also be used to determine suitable sites for mussel translocations. However, my criteria require further testing in other rivers before they can be transferred beyond the Clinch River. Behavior and physiological responses to laboratory manipulations of flow velocity and substrate particle size were used to elucidate microhabitat preferences of Actinonaias pectorosa, Potamilus alatus, and Ptychobranchus subtentum. These species appeared less stressed in the fastest flow treatment, demonstrating significantly higher oxygen consumption and oxygen-to-nitrogen (O:N) ratios than in slower flow treatments. Only P. alatus demonstrated a preference for substrate particle size, and consistently selected finer particle sizes. Actinonaias pectorosa and P. subtentum demonstrated preference for fast-flow microhabitats by readily burrowing in those conditions, while abandoning slow-flow conditions. The lack of preference for substrate particle size demonstrated by A. pectorosa and P. subtentum supports conclusions of previous studies that substrate particle size is of little or secondary importance for explaining mussel microhabitat use. These results, along with previous studies in the Clinch River, demonstrate that the stable habitats of riffles and runs; characterized by fast flows during summer low flows, low percent bedrock, and low embeddedness, are the most suitable habitats for mussel assemblages. To create and maintain suitable habitat conditions in tailwaters, releases should maintain flow over riffles at a minimum depth of no less than 30 cm in riffles that provide higher shear stress conditions (FST number > 7) and velocities (> 0.70 m/s). Periodic releases that are sufficient to transport silt and sand, but not high enough to transport larger substrate should be adequate to maintain substrates with a low degree of embeddedness. Doing so would create suitable habitat for all mussels, from the most to least specialized. Additionally, HSC developed for FFS and FFG guilds can be used to determine suitable destination sites for translocations of species belonging to these guilds.
  • Thumbnail Image
    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.
  • Thumbnail Image
    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.
  • Thumbnail Image
    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.
  • Thumbnail Image
    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.
  • Thumbnail Image
    Estimating Metabolism of Fish in Aquacultural Production Systems
    Neill, W. H.; Oborny, E. L. Jr.; Craig, Steven R.; Matlock, M. D.; Gatlin, D. M. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2003-06-01)
    Open-system respirometry offers a practical approach for measuring metabolic rates of fish cultured at high densities in uncovered raceways. Central to this methodology is analysis of a dynamic mass-balance on oxygen supply and demand. Here, we present a validated mass-balance equation, describe minimally disruptive procedures for estimating its parameters, and illustrate its use in estimating the oxygen-uptake rate of fish as a group, in real time and under actual production conditions.
  • Thumbnail Image
    An Evaluation of Adult Freshwater Mussels Held in Captivity at the White Sulphur Springs National Fish Hatchery, West Virginia
    Boyles, Julie L. (Virginia Tech, 2004-02-06)
    Due to the increasing need to provide refugia for freshwater mussels impacted by anthropogenic activities and exotic species, facilities should be identified and protocols developed for holding mussels in captivity. White Sulphur Springs National Fish Hatchery (WSSNFH), White Sulphur Springs, WV, has held freshwater mussels for nearly eight years, and has the potential to become an important refugium and propagation facility for conservation of mussels in the Ohio River Basin and elsewhere. The goal of this study was to determine the feasibility of holding adult freshwater mussels in long-term captivity at WSSNFH by evaluating survival, energy reserves, and gametogenesis of captive mussels in a recirculating pond system. I relocated three mussel species in the summer of 2001 and 10 mussel species in the summer of 2002 to a recirculating pond system (reservoir and raceway) at the hatchery. Water quality parameters of pH, alkalinity, hardness, temperature, and dissolved oxygen; and algal concentrations were measured periodically from summer 2001 to summer 2003. Annual survival rates of 10 species were estimated (August 2002 to August 2003) using the program MARK. Glycogen, protein, and lipid concentrations in mantle tissue of three captive species (Actinonaias ligamentina, Cyclonaias tuberculata, and Tritogonia verrucosa) were compared to those of wild mussels in the New River. Gametogenic activity and synchrony in A. ligamentina and C. tuberculata were compared between captive and wild mussels. Water quality parameters, with the exception of temperature, were within desirable ranges for most of the study. Temperatures of > 28° C were observed for several days during summers 2002 and 2003. Algal concentrations averaged 1903 cells ml-1 in the raceway (range: 300 to 4658 cells ml-1), which is comparable to algal concentrations reported for nearby rivers. The overall survival rate for 10 freshwater mussel species held in the raceway for one year was 77%. Villosa vanuxemensis had the highest survival rate (96%), and Lampsilis cardium had the lowest survival rate (31%). Although there were fluctuations in glycogen, protein, and lipid levels over 2 yr, there were no overall differences in energy substrates between captive and wild mussels at the end of the study. Captivity did not appear to have a negative affect on gametogenesis. Captive C. tuberculata spawned within the expected time frame between January and June, but slightly earlier than their wild counterparts in the New River. Due to the infestation of the gonads of both captive and wild A. ligamentina by digenean trematodes, little gametogenesis was observed. However, captive holding did not appear to have an effect on trematode infestation rates. From these results, I conclude that captive holding conditions in the recirculating pond system at WSSNFH were adequate for long-term holding of a wide range of mussel taxa. I recommend that WSSNFH continue to be used as an adult holding facility. Further research should be conducted to determine food and habitat preferences of freshwater mussel species in captivity so that optimal holding conditions can be provided for each species.
  • Thumbnail Image
    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.
  • Thumbnail Image
    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 μm). 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 μm). 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.
  • Thumbnail Image
    Intensive Marine Finfish Larviculture
    Schwarz, Michael H.; Delbos, Brendan C.; Mclean, Ewen; Craig, Steven R. (Virginia Cooperative Extension, 2009-05-01)
    Provides basic information on marine finfish larviculture including nutritional requirements that must be met and limitations.
  • Thumbnail Image
    Intensive marine finfish larviculture
    Schwarz, Michael H.; McLean, Ewen; Craig, Steven R.; Ovissi, Reza; Delbos, Brendan; Ovissipour, Mahmoudreza (Virginia Cooperative Extension, 2019)
    Marine finfish production is a rapidly expanding field, both in research and industrial aquaculture. They have inherently high value and are a relatively robust prospect for investment. Larvaculture.
  • Thumbnail Image
    A Needs Assessment of Aquaculture Extension Agents, Specialists, and Program Administrators in Extension Programming
    Schwarz, Michael H. (Virginia Tech, 2005-11-18)
    The purpose of this study was to identify continuing education and training needs of aquaculture Extension agents, specialists, and program administrators on the list serve AQUA-EXT. Ten competency areas were evaluated regarding perceived importance, and need for continuing education or training. In addition, 14 resources on the Aquaculture Network Information Center (AquaNIC) website were evaluated from this population for frequency of use and recommended improvements. Lastly, demographic data were collected to determine possible relationships to continuing education and training needs. The survey population was the AQUA-EXT list serve membership (N = 223), of which 174 responded. AQUA-EXT is a Web based mail group established by the Cooperative State Research, Education, and Extension Service as a means of disseminating information to the Extension community with work and interest in aquaculture. Data were collected with an online survey conducted via the interactive and encrypted Web site www.survey.vt.edu. Upon completion, data were exported into, and analyzed via the Statistical Package for the Social Sciences (SPSS). A majority of Extension agents, specialists, and program administrators did not require significant continuing education or training to accomplish their work effectively. However, general agreement among the three groups was for continuing education in the areas of program evaluation, information technologies, and human development. Regarding the AquaNIC website, 52% of Extension agents, 71% of specialists, and 81% of program administrators reported having used AquaNIC, however, use was infrequent. Recommendations to enhance Web site utility focused on requests to update and incorporate more comprehensive and in-depth information for all resource areas. Demographics indicated that mean ages for Extension agents, specialists, and program administrators were 47.9, 50.5, and 51.5 years respectively. Sixty three percent of agents indicated having master's degrees, and 63% and 72% respectively of specialists and program administrators indicated having doctorates. Means for years in their present position were 13.4, 13.2, and 8.4 years respectively for Extension agents, specialists, and program administrators, and 16.6, 16.1, and 15.5 respectively regarding total years in Cooperative Extension or Sea Grant. No statistical relationships between demographics and continuing education and training needs for Extension specialists, specialists, and program administrators were found.
  • Thumbnail Image
    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.
  • Thumbnail Image
    Production of Eicosapentaenoic acid from biodiesel derived crude glycerol using fungal culture
    Athalye, Sneha Kishor (Virginia Tech, 2008-07-07)
    Omega-3 polyunsaturated fatty acids, eicosapentaenoic acid (EPA, C20:5, n-3) and docosahexaenoic acid (DHA, C22:6, n-3), have many medically established benefits against cardiovascular diseases, cancers, schizophrenia, and Alzheimer's. Currently, fish oil is the main source of omega-3 fatty acids, but there are many problems associated with it such as undesirable taste and odor, and heavy metal contamination. As a result, it is necessary to seek alternative production sources based on various microorganisms. In this thesis we have developed a novel microfungal culture process to produce EPA from the crude glycerol byproduct generated in biodiesel industry. This process provides both an alternative source of omega-3 fatty acids and a benefit to the biodiesel industry. Indeed, as oil prices reach historical highs, biodiesel has attracted increasing interest throughout the United States. The disposal of the crude glycerol byproduct has been a challenge faced by the biodiesel producers. Crude glycerol presents a cheap carbon source for growth of many microorganisms. In this thesis, we tested the feasibility of using crude glycerol for producing eicosapentaenoic acid (EPA, 20:5, n-3) by one algal species, Phaeodactylum tricornutum and two fungal species, Mortierella alpina and Pythium irregulare. We observed that the algal growth is inhibited in the crude glycerol while the fungi can grow very well in crude glycerol-containing medium. The fungus M. alpina produced significant amount of ARA but negligible amount of EPA. P. irregulare produced significant amount of biomass as well as a relatively high level of EPA. The maximum dry biomass for the P. irregulare culture was 2.9 g/L with an EPA productivity of 7.99 mg/L-day. Based on these results, we concluded that P. irregulare was a promising candidate for EPA production from biodiesel derived crude glycerol. Further optimization work showed that P. irregulare grown 30 g/L crude glycerol and 10g/L yeast extract results in the highest level of EPA production. A temperature of 20o C is optimal for high fungal biomass and EPA levels. Addition of vegetable oil (at 1%) enhanced the EPA production and almost doubled the amount of biomass reached. Soap inhibits growth as well as EPA production severely even in small amounts. Methanol completely inhibits growth. The final optimized growth conditions for the fungus P.irregulare were a medium with 30g/L of crude glycerol, 10 g/L of yeast extract at a pH of 6 with 1% supplementation of oil, at a temperature of 20o C for a period of 7 days.Thus we have established that the fungus P.irregulare can be used successfully to produce high mounts of EPA from crude glycerol.
  • Thumbnail Image
    Responses of Nitrifying Bacteria to Aquaculture Chemotherapeutic Agents
    Cheatham, Amy Kathleen (Virginia Tech, 2009-01-27)
    As in any animal production industry, disease is inevitable; therefore, it is imperative that aquaculturists are able to effectively manage the disease and maintain their high production levels in an effort to bridge the gap between supply and demand in the seafood industry that has been caused in part by global over-fishing. This management responsibility lies not only in understanding the impact of the treatment on the cultured species, but also in understanding the impact of the treatment to the aquaculture system as an ecosystem. Currently, there is a narrow variety of chemicals approved by either the Food and Drug Administration (FDA) or the Environmental Protection Agency (EPA) for the treatment of disease outbreaks and water quality issues in aquaculture. Approved chemotherapeutants include oxytetracycline, Romet-30®, copper, and formalin. Additionally, a number of chemicals, such as Chloramine-T and potassium permanganate, are used off-label for the treatment of aquaculture systems. In this research, these six more commonly used chemotherapeutants were analyzed for their impacts to the nitrifying bacteria in aquaculture systems. It was found that three of the chemotherapeutants: oxytetracycline, Romet-30®, and chelated copper caused inhibition to the nitrifying bacteria at the whole cell level as demonstrated in the results from water quality and specific oxygen uptake rate analyses. The nitrification process resumed once the chemotherapeutant was removed from the system, either by a mandatory water change or by natural degradation. The other three chemicals: formalin, Chloramine-T, and potassium permanganate did not result in any significant inhibition to the nitrification process. Experiments on laboratory-cultured nitrifying bacteria confirmed these findings. These experiments also resulted in the observation that the expression of amoA was upregulated by the copper exposure and inhibited by oxytetracycline and Romet-30®, but began to resume as the antibiotics degraded. Comprehensively, the findings of these analyses demonstrated that, although nitrifiers are well-known to be sensitive to their environment, the ability of nitrifying bacteria to continue their oxidative processes following exposure to chemical stress is inherent to the bacteria themselves rather than simply occurring under the protection of a biofilm community as has been suggested.
  • Thumbnail Image
    Restoration of the endangered Cumberland elktoe (Alasmidonta atropurpurea) and Cumberland bean (Villosa trabalis) (Bivalvia: Unionidae) in the Big South Fork National River and Recreation Area, Tennessee and Kentucky
    Guyot, Jennifer Ann (Virginia Tech, 2005-12-16)
    The Big South Fork National River and Recreation Area (NRRA), located in Tennessee and Kentucky, has prepared a management plan to include restoration of its mussel fauna to historic levels. Restoration activities include propagation of juvenile mussels and relocation of adults to suitable sites in the Big South Fork of the Cumberland River (BSF) and its tributaries. This study was conducted to identify host fish for Cumberland elktoe (Alasmidonta atropurpurea) and Cumberland bean (Villosa trabalis), to determine suitable juvenile culture conditions for Epioblasma brevidens and V. trabalis, and to locate sites important to future mussel restoration efforts in the NRRA. Host fish identifications and propagation techniques were determined for two of the endangered species in the NRRA, Cumberland elktoe (Alasmidonta atropurpurea) and Cumberland bean (Villosa trabalis). Of seven host species tested, banded sculpin (Cottus carolinae) was the most suitable host fish for propagation of A. atropurpurea. Of five host species tested, fantail darters (Etheostoma flabellare) were the most suitable host fish for propagation of V. trabalis. Culture techniques to raise juvenile mussels in captivity were evaluated, using newly metamorphosed juveniles of V. trabalis and E. brevidens in recirculating systems. No differences in juvenile growth or survival were detected among substrates used (fine sediment, coarse sand, and a mixture of the two). Recirculating system design seemed to affect juvenile growth and survival; however, variable condition of juveniles also seemed to affect results, making it difficult to determine effects from trial treatments. Finally, an assessment of potential sites in the NRRA for restoration activities was conducted using spatial analysis in a geographic information system (GIS) and several measures of conservation value. Mussel restoration sites were assessed for potential threats from adjacent land uses that may negatively affect mussels, including coal mines, oil and gas wells, transportation corridors, agriculture and urban development. Sites were also evaluated on their current conservation value to designate which sites are most important to long-term maintenance of mussel fauna. Several sites were identified that contain relatively few land-use threats, and are appropriate for mussel restoration activities, including Big Island, Station Camp Creek, and Parchcorn Creek sites on the mainstem BSF, as well as sites on Clear Fork and North White Oak Creek. Many of these sites also have high conservation values. Other sites had relatively high land-use threats that need to be addressed before restoration activities take place. Such sites include Leatherwood Ford, Rough Shoals Branch, Blue Heron, and Yamacraw on the mainstem BSF. The dominant threat to most sites came from transportation corridors, whereas some sites in southern and eastern portions of the watershed also were threatened by coal mines, and oil and gas wells.
  • Thumbnail Image
    Understanding Fish Nutrition, Feeds, and Feeding
    Craig, Steven R.; Helfrich, Louis A. (Virginia Cooperative Extension, 2009-05-01)
    Provides basic information about the development of new species-specific diet formulations that support the aquaculture industry as it continues to expand to meet demands.