Date Awarded

2011

Document Type

Thesis

Degree Name

Master of Science (M.Sc.)

Department

Virginia Institute of Marine Science

Abstract

One system used for bivalve mollusc culture is flowthrough larval culture, which provides a continuous flow of food and seawater to the tank. Flowthrough culture enables larvae to be reared at stocking densities up to 100 larvae/mL, a characteristic that should recommend it as the culture system of choice for the East coast; however, Eastern oyster larvae have never been tested in flowthrough culture, discouraging implementation of the system. The thesis objectives are designed to address questions regarding the survival, growth, competent period, cell consumption, growth efficiency, and cell selection of oyster larvae reared in flowthrough culture. The objectives are: to describe larval tolerance to metabolic waste products, to determine how stocking densities influence clogging of the banjo screen and how those stocking densities coupled with exchange rate influence survival, growth, duration of the competent period, cell consumption, and cell selectivity, and to examine replication of flowthrough culture and establish data for the variables measured. To obtain a basic understanding of larval tolerance to their metabolic waste, twelve static tanks were set up at the Aquaculture Genetics and Breeding Technology Center’s hatchery at the Virginia Institute of Marine Science. Larvae were exposed to a range of concentrations of ammonia, nitrite, and nitrate and their survival and growth were monitored. Ammonia was the only metabolic waste that caused detrimental effects to larvae at a concentration of 10 mg/L. To address the remaining objectives, six 400 L conical flowthrough tanks were set up at Oyster Seed Holdings, a commercial hatchery. To determine if banjo screen clogging (the cause of tank overflow) was affected by the day and density at which larvae were introduced to flowthrough culture, larvae were introduced at two days old at three different stocking densities. The banjo screen, a circular plastic band with mesh screen on both sides, retains larvae in flowthrough culture while allowing water to exit. The banjo screen was monitored for clogging every 12 hours for 60 hours. Larvae can be introduced to flowthrough culture at two days old at densities as high as 50 larvae/mL without risking banjo clogging. To examine the effects of different flowthrough culture parameters on larval development, larvae were stocked in flowthrough cultures at 10, 20, and 50 larvae/mL and reared at five and ten exchanges of water/day. Five exchanges of water/day and a stocking density between 10 – 20 larvae/mL resulted in the highest survival, fastest growth, and greatest amount of competent larvae harvested. Variation among flowthrough cultures stocked with 10 larvae/mL and reared at five and ten exchanges of water/day was examined. Five exchanges of water/day generally had lower variation, with the smallest being survival and length. The results for survival, length, cell consumption, duration of the competent period, and growth efficiency were characterized as the established values for the thesis’s flowthrough system and were compared with data obtained from the controls in Chapter Three to distinguish anomalous data.

DOI

https://dx.doi.org/doi:10.25773/v5-2s4b-k150

Rights

© The Author

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