Journals, Virginia Tech Publishing

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Browsing Journals, Virginia Tech Publishing by Department "Fish and Wildlife Conservation"

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    Characteristics of the Recirculation Sector of Finfish Aquaculture in the United States and Canada
    Delabbio, Juliette L.; Murphy, Brian R.; Johnson, G. R.; Hallerman, Eric M. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2003-06-01)
    In the autumn of 2001, a survey was conducted to examine basic farm production and human resource characteristics of recirculation facilities in the United States and Canada currently growing finfish. An 86% response rate was achieved. The survey data indicate that this sector of aquaculture is quite heterogeneous. The number and pounds of fish produced is quite variable, with presence of small-, medium- and large­ sized farms in this sector. Recirculation technologies are employed to culture a wide variety of both warmwater and coldwater fishes in both saltwater and freshwater situations. The four fishes most commonly grown in recirculation units in the United States and Canada are Atlantic salmon smolts, tilapia, hybrid striped bass and ornamental fishes. A high proportion of facilities using recirculation technologies use pumped groundwater as a primary water source. Over 40% of facilities represented in the survey rely on a single water source to sustain their operation and have no secondary water source as backup. Management personnel of recirculation facilities are highly educated; more than 74% of respondents reported holding at least an undergraduate degree. The majority of personnel managing recirculation facilities are middle-aged individuals who have over 10 years of related work experience. The findings of this study represent the first empirical description of the recirculation sector of finfish aquaculture in the United States and Canada.
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    Hatchery and Grow-out Performance of Sunshine Bass and Backcross Hybrid Striped Bass in Recirculating Aquaculture Systems
    Lindell, S.R.; Delbos, B.; Perham, R.; Goldman, J.; Hallerman, Eric M.; Brenden, T. O. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2004-06-01)
    Previous research has suggested that backcross hybrid striped bass (BX: sunshine bass female x striped bass male) perform as well as F1 hybrid striped bass (sunshine bass: white bass female x striped bass male) for many economically important traits. We conducted trials to compare rearing and growth traits of selected backcross hybrid striped bass with hybrid striped bass (HSB). We spawned and reared larval BX fry in two hatchery cycles, measured fry growth and performance, and compared them to past performance of HSB fry. We conducted a grow-out trial of commercially-available hybrid striped bass versus backcross hybrid striped bass in replicated tanks to phase II fingerling size (approximately lOOg). Compared to HSB, in the hatchery phase, backcross hybrid striped bass exhibited lower fertilization rate, comparable swimbladder inflation rate, shorter time-to-weaning, lower survival, comparable growth, and comparable condition factor. After 60 days, HSB exhibited significantly better growth, survival, and feed conversion efficiency than BX. However, BX may have better potential market acceptance by virtue of having a lower condition factor, appearing longer and less deep-bodied than HSB.
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    Water Quality Impacts of Three Biofilter Designs in Recirculating Aquaculture Systems
    Hall, A. G.; Hallerman, Eric M.; Libey, George S. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2002-06-01)
    Nine recirculating aquaculture systems utilizing three biofilter types were placed on line and stocked with yellow perch, Percaflavescens, fingerlings. Biofilter type differed among systems, and included upflow pulsed bed bead filter, packed tower trickling filter, and rotating biological contactor. Following filter acclimation, a comparative analysis of biofilter performance was conducted, involving measurement of temperature, pH, dissolved oxygen, total ammonia-nitrogen, nitritenitrogen, nitrate-nitrogen, alkalinity, total hardness, carbonaceous biochemical oxygen demand, dissolved organic carbon, and total suspended solids. Filter bed emergence promoted effective carbon dioxide stripping, pH maintenance, and consistent nitrification performance in trickling filters and rotating biological contactors. Higher total ammonia nitrogen mass removal rates were observed in trickling and rotating biological contactor filters than in bead filters. Low total ammonia nitrogen mass removal rates and nitrification efficiencies for all filters resulted from relatively high carbonaceous biological oxygen demand loadings. Analysis of areas under mass removal curves showed that RBC filters were surface area limited. Foam formation in trickling filters effectively removed total suspended solids from the culture water. Filter type did not have a significant effect on median organic water quality parameter values in the production tanks. Although differences in nitrification performance and certain water quality parameters were observed between filter types, the data set did not indicate that one filter type should be considered generally most effective at treating wastewater produced in a recirculating aquaculture system.