Culture Methods for Growth Enhancement and Off-Season Production of Yellow Perch Perca flavescens

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Title: Culture Methods for Growth Enhancement and Off-Season Production of Yellow Perch Perca flavescens
Author: Shewmon, Laura Norkio
Advisors: Dr. John Godwin, Committee Member
Dr. Tom Losordo, Committee Member
Dr. Harry Daniels, Committee Chair
Abstract: The success of the yellow perch Perca flavescens aquaculture industry depends largely on increasing growth efficiency to reduce production costs, and increasing fingerling availability for year-round production. Two characteristics of yellow perch biology pose challenges toward these goals. 1) Yellow perch exhibit sexually dimorphic growth, detected concurrently as the fish enter puberty, with many slower-growing males that may never achieve market size. These growth differences between genders also promote a situation in which cannibalism can quickly deplete a perch population reared under intensive conditions. 2) Yellow perch spawn once a year in the spring, and most producers are limited to a production schedule centered on this event. Two sets of studies were conducted to evaluate culture methods for the inhibiting maturation for promotion of somatic growth, and evaluate the practice of 'cold-banking' for off-season fingerling availability. Four combinations of constant and natural photothermal regimes were used to impose environmental conditions on juvenile fish that inhibited maturation and promoted somatic growth. Immature perch were expected to demonstrate reduced dimorphic growth pattern and overall growth enhancement. Results indicate that a) constant temperature is the strongest promoter of overall growth regardless of photoperiod; b) constant photoperiod also promotes overall growth regardless of temperature; c) natural (decreasing) photoperiod initiates maturation in yellow perch regardless of temperature; d) natural temperature is required for late maturational processes; e) constant temperature and constant photoperiod together confer the best overall growth performance, fully inhibit maturation in both genders, and suppress a sexually dimorphic growth pattern up to 53g average weight. Two studies were conducted evaluating the growth of cold-banked fish and costs associated with commercial application of this culture technique. Perch banked at 10 C on a reduced ration for 60 and 180 days were reared up to 240 and 120 days post-banking respectively. Post-banking culture conditions (and 0 days banked control conditions) were satiation feeding at 22 C. Growth, SGR, and feed conversion did not differ among the 60-day, 180-day treatments and controls up to 120 days post-banking. Growth, specific growth rate (SGR), and feed conversion did not differ between controls and 60-day treatment up to 240 days post-banking. The additional cost of cold banking yellow perch on a commercial scale was evaluated at Deca-J Farms (Clinton, NC) for 4 groups of fish cold banked (11 C, restricted ration) for four different durations (98, 169, 238, and 308 days). Growth was compared to controls (0 days banked, 24 C, satiation feeding) over 60 days post-banking. Growth observations indicated that perch grew during banking and post-banking SGR was negatively correlated with banking duration. Cold banking at Deca-J farms cost an estimated additional $0.15 per fish, with $0.09 per fish attributed to maintenance (variable) costs.
Date: 2005-10-25
Degree: MS
Discipline: Zoology

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