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-mu-m, shrimp growth rates increased by 53% over growth rates attained in clear well water, while solids > 5.0-mu-m improved shrimp growth by an additional 36%. These solids consisted predominantly of microalgae and microbial-detrital aggregates. Solids < 0.5-mu-m, 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.