The effects of soil and water hardness on growth and survival of red swamp crawfish, Procambarus clarki, were studied in plastic pools. Pools had no soil or Calhoun soil, with water hardnesses adjusted with calcium chloride to 9, 50, 100 or 150 parts per million, or pools had Sharkey soil with water hardnesses of 50, 100, 150 or 200 ppm. Water hardness was the most significant factor affecting growth and survival of crawfish. As water hardness increased, so did the mean weight gain and per cent survival. At 9 ppm water hardness, the presence of soil resulted in similar weight gain per crawfish as in no-soil pools but crawfish survival in pools containing soil was 53 to 77 per cent and only 9 per cent in pools with no soil. Good growth of crawfish occurred in the absence of soil, if water hardness was high. The highest mean weight gain per crawfish and per cent survival were in pools containing Sharkey soil. Average production per acre figures ranged between 28 to 411 pounds per acre with the greatest production from a single pool being 778 pounds per acre. The average growth period was 36 days.
