Gary D. Pruder

Characterization of organic particles associated with rapid growth in juvenile white shrimp, Penaeus vannamei Boone, reared under intensive culture conditions

Aquaculture ponds possess unique ecological characteristics which contribute significantly to the growth and survival of the target species. In this study, shrimp growth rates were monitored in microcosm tanks containing flow-through water with varying concentrations of organic particles produced autochthonously in an intensive shrimp pond. Rapid growth occurred in unfiltered pond water with a mean particulate organic carbon (POC) concentration of 6.98 mg/l over six sampling days. In contrast, slowest growth occurred in well water with a mean POC concentration of 0.38 mg/l. Within the POC pool, as the percentage of living carbon increased, shrimp growth rates increased. Unfiltered pond water contained more than 45% living carbon, whereas well water had greater than 85% detrital carbon. Living biomass was dominated by pennate and centric diatoms, whereas contributions from bacteria and protozoans were minor. There was a highly significant linear relationship between shrimp growth and POC concentration (r2 = 0.895, p < 0.0001), although there appeared to be a minimum threshold concentration below which shrimp growth was unaffected. Temporal variability in algal cell density (ACD) indicated a bloom and crash cycle, suggesting that the availability of live algal cells to shrimp was sporadic. Further research on pond ecology is needed in order to manipulate organic carbon pools to improve shrimp growth.

The relative enhancement of Penaeus vannamei growth by selected fractions of shrimp pond water

It is generally assumed that shrimp cultured in intensive aquaculture systems receive little or no nutrition from natural pond biota. However, recent experiments indicate that even under intensive growout conditions, shrimp growth is enhanced by unknown growth factors produced autochthonously in an intensive shrimp pond. As part of an ongoing research effort to characterize the growth factors contained in shrimp pond water, an experiment was conducted to compare the effects of pond water, with selected solid fractions removed, on the growth of juvenile white shrimp, Penaeus vannamei. Fractions were removed from pond water by passing the water through a series of mechanical and activated carbon filters. In the presence of water-column solids between 0.5 and 5.0 μm, shrimp growth rates increased by 53% over growth rates attained in clear well water, while solids > 5.0 μm improved shrimp growth by an additional 36%. These solids consisted predominantly of microalgae and microbial-detrital aggregates. Solids <0.5 μm, including dissolved organic carbon, did not appear to contribute to shrimp growth. Water-column solids produced autochthonously in shrimp ponds are also known to improve growth in oysters, brine shrimp, and calanoid copepods. Efforts continue to further characterize these solids and to explore the possibility of their extraction, preservation, and use as feed additives.

The role of CO2 enrichment of aerating gas in the growth of an estuarine diatom

The effect of carbon dioxide concentration on the growth of Thalassiosira pseudonana (Hustedt) Hasle and Heimdal clone 3H was studied at three light intensity levels and two oxygen concentrations. Algal cultures were grown in an enriched artificial seawater medium under constant illumination in 500 ml gas wash bottles. Population density, particulate carbon and particulate nitrogen were measured periodically during exponential growth. Growth rate did not increase as the CO2 concentration was elevated above 16.0 μmole/l. Freshly inoculated algal cultures did not grow in an organic carbon-free medium bubbled with CO2 -free air. The kinetics of inorganic carbon mobilization including concentrations, reaction rates, and CO2 transport, generation and uptake are analyzed.

Mariculture of shellfish in controlled environments: A prognosis

Abstract This paper seeks to define biological specifications for the design of highly controlled cultural systems for oysters and hard clams. Much of the biological information necessary for design either is not available in the literature or is available only in an inferential manner. Particularly lacking are equations describing relationships between size of the animals and their various physiological processes. Equations that estimate some of these relationships are presented, and safe levels of several water quality variables are defined.

A method of economic comparisons for aquaculture diet development

Abstract The benefits that can result from substituting non-living feeds for living feeds in the diets of aquatic animals include improved reliability of the food supply, predictability of diet composition and reduced feed cost. Experimental feeds or supplements will only be used for commercial production of aquatic animals if there is an expectation of increased profit. Many experimental diets are not transferred to commercial use, however, because there is no standard method for aquaculture nutritionists to evaluate relative profitabilities of new diets. We developed a model to assess the profitability of experimental diets, based on economic equations and experimentally determined values for feeding cost, growth rate, growth efficiency and mortality. The model was tested by examining the economic feasibility of substituting yeast for algae in diets for the hard clam, Mercenaria mercenaria (L.), and by examining literature data for feeding studies with carp, Cyprinus carpio L.