Fish Ecology and Fisheries - Freshwater Ecology: Concepts and Environmental Applications - page 445

10 6

10 5

10 4

10 3

Mollusks
Crayfish

Shrimp Catfish Trout Tilipia

Carp Milkfish Salmon

FIGURE 21.12 Global production of selected freshwater organisms by aquaculture in 1989;
note the log scale on the y axis (data from Stickney, 1994).

practices including use of disease-free stock must be followed. Some in-
vertebrate parasites are transmitted via intermediate invertebrate hosts,
such as snails and polycheate worms. In this case, disease prevention may
include use of pesticides and pond draining to kill the intermediate hosts.
Perhaps the most ecologically advanced form of aquaculture is the
polyculture of carp in Southeast Asia. This polyculture system was devel-
oped over centuries by fish farmers using close observation of the ponds
and trial and error rather than by academic ecologists. The first topic on
aquaculture was written in Chinese in 460 BC (Fichter, 1988). The systems
were developed to utilize several species with varied food requirements,
and the excretion of one species fertilizes the growth of food for the other
(Zweig, 1985). The dominant fishes in the Chinese systems are common
carp ( Cyprinus carpio, omnivore, benthic), bighead carp ( Hypoph-
thalmichthys nobilis, zooplanktivore), grass carp ( Ctenopharyngodon
idella, herbivore), and silver carp ( Hypophthalmichthys molitrix, phyto-
planktivore). In India, the catla (Catla catla), rohu (Labeo rohita), and mri-
gal (Cirrhinus mrigala) are used. There are about 2.5 million ha of carp
ponds in India and China. In most cases, these ponds are fertilized with
manure, and fish are fed with vegetation or invertebrates. It takes 20 years
of training to become adept at all the techniques of disease control, fish
feeding, manipulation of reproduction, and fertilization associated with
these traditional forms of fish culture (Zweig, 1985).

SUMMARY

1. Biodiversity of fish is related to factors that operate at a variety of
temporal and spatial scales. In general, fish communities are more
diverse in tropical areas, on large landmasses, in older drainage
basins, where greater habitat diversity exists, and where more prey
species exist.