THE GROWTH RATE OF OYSTERS HELD IN THE INTAKE AND DISCHARGE CANALS OF AN ELECTRIC GENERATING STATION AND IN NATURAL WATERS

Oysters (Crassostrea virginica) were held during the spring of 1976 in the intake and discharge canals at the P. H. Robinson Generating Station, Bacliff, Texas and in Galveston Bay at San Leon, Texas. Oysters in the discharge canal increased in weight significantly faster than in the intake canal or Galveston Bay. There was no significant difference between the weight increases in the intake canal and in Galveston Bay. No clear pattern of increase in length could be detected at the three stations. Although oysters in the discharge canal exhibited some degree of greening, the condition of the oysters from all three stations was good. The level of infection of Labyrinthomyxa was relatively low in oysters from all three stations; however, the incidence of infection was significantly greater in the discharge canal. Fouling organisms increased in weight in the discharge canal at a rate about twice that in the intake canal and Galveston Bay. Fouling could be controlled by exposing the oysters to air once each week for a period of 4–8 hr. Mortality, which was low at all stations, occurred early in the experiment and was probably due to initial culling stress. However, oysters held in the discharge canal beyond the study period died when water temperatures reached 37.5–39°C. The results of this experiment indicate that the growth rate of oysters can be significantly increased in a power plant discharge canal, provided that some means, such as cooling towers, are applied to keep high summer temperatures below lethal values.