Page 161 - Understanding NCERT Science 09

beyond it. Popular marine fish varieties In such a system, a combination of five or
include pomphret, mackerel, tuna, sardines, six fish species is used in a single fishpond.
and Bombay duck. Marine fish are caught These species are selected so that they do
using many kinds of fishing nets from fishing not compete for food among them having
boats. Yields are increased by locating large different types of food habits. As a result, the
schools of fish in the open sea using satellites food available in all the parts of the pond is
and echo-sounders. used. As Catlas are surface feeders, Rohus
Some marine fish of high economic value feed in the middle-zone of the pond, Mrigals
are also farmed in seawater. This includes and Common Carps are bottom feeders, and
finned fishes like mullets, bhetki, and pearl Grass Carps feed on the weeds, together these
spots, shellfish such as prawns (Fig. 12.5), species (Fig. 12.6) can use all the food in the
mussels and oysters as well as seaweed. pond without competing with each other. This
Oysters are also cultivated for the pearls increases the fish yield from the pond.
they make.

(a)
(b)
Macrobrachium rosenbergii Peneaus monodon
(fresh water) (marine)

Fig. 12.5 : Fresh water and marine prawns
(c)
(d)
As marine fish stocks get further depleted,
the demand for more fish can only be met by
such culture fisheries, a practice called
mariculture.

12.2.3 (ii) INLAND FISHERIES (e)

Fresh water resources include canals, ponds, (f)
reservoirs and rivers. Brackish water
resources, where seawater and fresh water Fig. 12.6: (a) Catla (b) Silver carp (c) Rohu (d) Grass
mix together, such as estuaries and lagoons Carp (e) Mrigal (f) Common Carp
are also important fish reservoirs. While
capture fishing is also done in such inland One problem with such composite fish
water bodies, the yield is not high. Most fish culture is that many of these fish breed only
production from these resources is through during monsoon. Even if fish seed is collected
aquaculture. from the wild, it can be mixed with that of
Fish culture is sometimes done in other species as well. So, a major problem in
combination with a rice crop, so that fish are fish farming is the lack of availability of good-
grown in the water in the paddy field. More quality seed. To overcome this problem, ways
intensive fish farming can be done in have now been worked out to breed these fish
composite fish culture systems. Both local in ponds using hormonal stimulation. This
and imported fish species are used in such has ensured the supply of pure fish seed in
systems. desired quantities.

IMPROVEMENT IN FOOD RESOURCES 149

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