Supplemental Feeding of Oysters with Starch

Abstract

Effects of carbohydrate supplements on shell and tissue (meats) growth of the oysterCrassostrea virginica were evaluated by laboratory studies. During spring, the addition of about 5 ppm cornstarch or wheat flour to York River water flowing at optimum rates had no detectable effect on shell or meat development. Similar studies in fall resulted in a significant increase in tissue weights of oysters but no effect on shell size. Tissue development was inhibited if the water supply was restricted or if the inflowing water was initially passed over a large group of actively feeding oysters, (“pre-filtered”). Under these conditions wheat or cornstarch at about 5 to 32 ppm partially or wholly compensated for effects of reduced flows or pre-filtered water on meat development. Effects on shell size were inconclusive. Concentrations of 2 to 5 mg/l dextrose added to inflowing water had no influence on shell or tissue growth. At 34 mg/l there was a significant effect on meat development, but no detectable effect on shell measurements. The study suggests that under estuarine conditions, tissue weights of oysters may beinfluenced by quantities of starch in planktonic algal cells rather than by the species or volume of plankters ingested.