ESTUARINE FISH FARMING
175
carbon dioxide higher than in the unfertilized controls, and (iii), a
sevenfold increase of blue-greens, a fourfold increase of diatoms, and a
3.5-fold increase of green algae over the unfertilized control. There
was no significant increase in the production of zooplankton. Saanin
and Tati Ramelan say that stable manure gives similar results, but high
transport costs make the use of city wastes (presumably night soil) and
stable manure from outside the pond area, uneconomical.
Copra-slime, the residue left after the extraction of the oil, was a
successful fertilizer. This easily decomposable by-product was tested
at dosages of 400-800 lblacre, and gave rise to a very good growth of
blue-greens. Schuster gives a graph which shows that 80 days after
the treatment with copra slime at the rate of 700-1 000 kglhectare, the
crop of algae so increased that the Chanos grew in weight from 20250 g, while in the unfertilized control pond Chanos, stocked at the
same rate, grew from 20 g to only 160 g. Less encouraging results were
obtained by the use of molasses, which were chiefly for the control of
cerithiid snails. Favourable results were got at first, but prolonged use
quickly led to the exhaustion of the soil.
I n Taiwan, organic fertilizers, such as various oilcakes, rice bran,
or pig and chicken manure, may be added to Chanos production ponds
at a time when the good growth of blue-greens, with which the season
began, starts to be cropped down. Some experimental work has been
done in Taiwan on the effectiveness of organic fertilizers in stimulating
algal growth. Lin (1968) quotes Yamamura’s tests with benthic algae,
chiefly Lyngbya spp. He applied fertilizer at a standard rate of 1 800
kglhectare, and each trial lasted 60-80 days. No fish were stocked.
Soybean cake gave the best results, producing 192g/day wet
weight of alga. Then followed a group of fertilizers including fish waste,
coconut cake, rice bran, castor-oil cake, night soil, and pig manure, all
of which gave about the same amount of algal growth, namely, 162172 g/m2 dry weight. Far behind came pineapple waste (115 g) and
potash (105 g/m2/day). This last result could have been expected, for
there is ample potash in brackish and sea water.
I n some commercial Chanos ponds the effect of organic fertilizers
was studied over a period of nine years (1957-1966). The highest fish
crop (1 900 kglhectare), was obtained by fertilizing with 1 000 kg/
hectare of rice bran, 970 of legume seed, and 250 kglhectare of peanut
meal. The next best results (1 700 kglhectare of fish each) were obtained
by fertilizing with 2 000 kg/hectare of rice bran, 800 of legume seed,
100 of peanut meal and 2 000 kglhectare of night soil; and by 1 700
kglhectare of rice bran and 900 kglhectare of night soil, respectively.
The poorest result was obtained (1 200 kglhectare of fish) with 970 kg/
175
carbon dioxide higher than in the unfertilized controls, and (iii), a
sevenfold increase of blue-greens, a fourfold increase of diatoms, and a
3.5-fold increase of green algae over the unfertilized control. There
was no significant increase in the production of zooplankton. Saanin
and Tati Ramelan say that stable manure gives similar results, but high
transport costs make the use of city wastes (presumably night soil) and
stable manure from outside the pond area, uneconomical.
Copra-slime, the residue left after the extraction of the oil, was a
successful fertilizer. This easily decomposable by-product was tested
at dosages of 400-800 lblacre, and gave rise to a very good growth of
blue-greens. Schuster gives a graph which shows that 80 days after
the treatment with copra slime at the rate of 700-1 000 kglhectare, the
crop of algae so increased that the Chanos grew in weight from 20250 g, while in the unfertilized control pond Chanos, stocked at the
same rate, grew from 20 g to only 160 g. Less encouraging results were
obtained by the use of molasses, which were chiefly for the control of
cerithiid snails. Favourable results were got at first, but prolonged use
quickly led to the exhaustion of the soil.
I n Taiwan, organic fertilizers, such as various oilcakes, rice bran,
or pig and chicken manure, may be added to Chanos production ponds
at a time when the good growth of blue-greens, with which the season
began, starts to be cropped down. Some experimental work has been
done in Taiwan on the effectiveness of organic fertilizers in stimulating
algal growth. Lin (1968) quotes Yamamura’s tests with benthic algae,
chiefly Lyngbya spp. He applied fertilizer at a standard rate of 1 800
kglhectare, and each trial lasted 60-80 days. No fish were stocked.
Soybean cake gave the best results, producing 192g/day wet
weight of alga. Then followed a group of fertilizers including fish waste,
coconut cake, rice bran, castor-oil cake, night soil, and pig manure, all
of which gave about the same amount of algal growth, namely, 162172 g/m2 dry weight. Far behind came pineapple waste (115 g) and
potash (105 g/m2/day). This last result could have been expected, for
there is ample potash in brackish and sea water.
I n some commercial Chanos ponds the effect of organic fertilizers
was studied over a period of nine years (1957-1966). The highest fish
crop (1 900 kglhectare), was obtained by fertilizing with 1 000 kg/
hectare of rice bran, 970 of legume seed, and 250 kglhectare of peanut
meal. The next best results (1 700 kglhectare of fish each) were obtained
by fertilizing with 2 000 kg/hectare of rice bran, 800 of legume seed,
100 of peanut meal and 2 000 kglhectare of night soil; and by 1 700
kglhectare of rice bran and 900 kglhectare of night soil, respectively.
The poorest result was obtained (1 200 kglhectare of fish) with 970 kg/