ESTUARINE FISH FARMING
203
suitable sites. Many operators are combining fish farming with the
manufacture of salt.
The greater part of the acreage of brackish-water fishponds was
built in earlier years, in the days of cheap labour. Since the war,
however, labour costs seem to have risen faster than the value oi the
fish obtained from the ponds, so efforts are being made towards an
intensification of culture, to give larger crops in the present ponds,
and so make investment in fishponds more profitable.
I n Hawaii, for instance, research is being done into means of increasing the productivity of the algal pasture which is the basis of the
primary production of the ponds. Hiatt (1944) suggested measures to
eliminate predatory fish, at present able to enter the ponds almost at
will (Malone, 1969). Means to reduce the turbidity of the ponds would
increase algal production.
I n all countries concerned, this increase of algal production is being
sought by the use of fertilizer. For instance while the recorded production of algal pasture at Taiwan, namely, 28 000 kglhectare wet
weight is nearly equal to that of " nori " (Porphyra) in Japan, itself
claimed to be equal to the highest land production of plants, the
experiments with Chlorella show how much further the culture of algae
as pasture can be taken. With this alga, a rate of production of 8-17
tons dry weight of alga per acre per year has been achieved ; or if we
assume that the alga contains 85% of water, the rate of production
of wet weight would be 45-96 tons per acre per annum. While it is
not suggested that these results, obtained under aquarium conditions,
could be equalled in the field and on the commercial scale, they do make
the point that there is still great room for increases in the productivity
of algal biomass, and thence of the fish which feed on algae and their
associated organisms. This is one of the most worth-while lines of
research waiting to be done.
I n India, Pillay (1954) suggested better arrangements for the stocking of the ponds. Selective stocking would give fewer predators in the
crop, and fishing in the shallows near the bheris would provide subsidiary fish and prawn fry. Pakrasi et al. (1964) also had in mind the
lack of a trade in fish fry, through which the ponds could be stocked with
controlled numbers of the desired kinds of fish. Saha et al. (1969) hoped
to replace naturally spawned fish fry with those of the valuable Indian
major carps, provided these could be acclimatized to live in the saline
ponds. Saha et al. (1969) worked out the occurrence and abundance
of the fry of fish valuable for pond stocking. They found, for instance,
that fry of the most popular species, Mugil parsia, was available in
the drains leading to the ponds a t almost all times of the year.
203
suitable sites. Many operators are combining fish farming with the
manufacture of salt.
The greater part of the acreage of brackish-water fishponds was
built in earlier years, in the days of cheap labour. Since the war,
however, labour costs seem to have risen faster than the value oi the
fish obtained from the ponds, so efforts are being made towards an
intensification of culture, to give larger crops in the present ponds,
and so make investment in fishponds more profitable.
I n Hawaii, for instance, research is being done into means of increasing the productivity of the algal pasture which is the basis of the
primary production of the ponds. Hiatt (1944) suggested measures to
eliminate predatory fish, at present able to enter the ponds almost at
will (Malone, 1969). Means to reduce the turbidity of the ponds would
increase algal production.
I n all countries concerned, this increase of algal production is being
sought by the use of fertilizer. For instance while the recorded production of algal pasture at Taiwan, namely, 28 000 kglhectare wet
weight is nearly equal to that of " nori " (Porphyra) in Japan, itself
claimed to be equal to the highest land production of plants, the
experiments with Chlorella show how much further the culture of algae
as pasture can be taken. With this alga, a rate of production of 8-17
tons dry weight of alga per acre per year has been achieved ; or if we
assume that the alga contains 85% of water, the rate of production
of wet weight would be 45-96 tons per acre per annum. While it is
not suggested that these results, obtained under aquarium conditions,
could be equalled in the field and on the commercial scale, they do make
the point that there is still great room for increases in the productivity
of algal biomass, and thence of the fish which feed on algae and their
associated organisms. This is one of the most worth-while lines of
research waiting to be done.
I n India, Pillay (1954) suggested better arrangements for the stocking of the ponds. Selective stocking would give fewer predators in the
crop, and fishing in the shallows near the bheris would provide subsidiary fish and prawn fry. Pakrasi et al. (1964) also had in mind the
lack of a trade in fish fry, through which the ponds could be stocked with
controlled numbers of the desired kinds of fish. Saha et al. (1969) hoped
to replace naturally spawned fish fry with those of the valuable Indian
major carps, provided these could be acclimatized to live in the saline
ponds. Saha et al. (1969) worked out the occurrence and abundance
of the fry of fish valuable for pond stocking. They found, for instance,
that fry of the most popular species, Mugil parsia, was available in
the drains leading to the ponds a t almost all times of the year.