ABSTRACT
In the natural aquatic environment, whether fresh water or marine, the first link in the food chain is always planktonic organisms. As has been shown in Chapter 2, phytoplankton (microalgae) represent the start of the planktonic food chain; they are the primary producers. Planktonic filter feeders, including larval molluscs, rotifers, copepods and artemia, and benthic filter feeders (molluscs), are the first level of consumers (herbivores); larval fish or crustaceans which consume rotifers and artemia are carnivores, representing the second level of consumption. The intensive fish hatchery (Part IV, Chapter 4) attempts to model the trophic web, raising each link separately. In extensive culture of fry or adult fish in ponds there is no such separation.
