The result of applying pre-flooding applications of simazine to warm-water hatchery ponds employed in the culture of largemouth bass, bluegill and channel catfish fingerlings is described. Rates of 10 and 15 pounds active simazine per acre appeared to reduce the incidence of algal growths such as Pithophora and Hydrodietyon and inhibited development of submerged rooted weeds. Effects generally persisted for one production period but were not noticeable in succeeding production cycles. Some indication was obtained that phytoplankton development was retarded but fish production was not appreciably lower in treated ponds that that in untreated ones. The development of zooplankton did not appear to be retarded by simazine applications to bass rearing ponds. Some advantages of pre-flooding treatment of warm-water hatchery ponds are discussed.
