178
C. F. HICKLING
Blanco and Acosta (1958) say that the supplementary foods for grey
mullet in the small subsistence ponds on Luzon consist of boiled
" camote )', rice bran, and corn meal, on which the fish grow fast. I n
the Russian limans, the overwintering grey mullet are fed with bloodworms, Daphnia, etc. and in Israel, where the grey mullet are grown
in ponds (in this case, fresh water or very slightly brackish water) in
company with common carp and species of Tilapia, they share with
these other fish the supplementary foods such as oilcakes and grains
which are given on a large scale t o achieve the very high rates of fish
production now customary in Israel. I n Japan, where grey mullets are
grown together with carp or eels, they share the supplementary foods
given to these other fishes, but probably feed mainly on the residues
and faeces which fall to the pond bottom (Asia Kyokai, 1957).
With the intensive rearing of the yellowtail and the Kuruma prawn
in Japan, the whole of the food supplied is supplementary food, since
the fish and prawns being cultivated are far too densely stocked for
natural foods to play any part in their growth. Success must depend
on finding a reliable source of food a t a price, delivered and dispensed
to the fish, which will enable the finished fish to be sold at a profit. I n
Taiwan, I was told that suitable trash fish could be bought in the market
for $2 per Ib, that the conversion rate when fed t o eels was 13 to 1, and
that the eels sold a t the luxury price of $80 per lb. At such prices,
there is a margin of profit, especially as the ponds also contain fish, such
as grey mullet, which feed on the food residues, and add to earnings
without adding to the cost.
VI. MANAGEMENT OF BRACKISH-WATER FISHPONDS
A. Tilapia
Tilapia, is the only fish cultivated in brackish-water fishponds
which will breed naturally there. I n fresh water it is a disappointing
subject for fish culture because in captivity it runts down to a small
and commercially valueless size. Various stratagems have to be
applied to avoid this runting and get marketable fish (Hickling, 1963).
However, in brackish water, maturity seems to be delayed somewhat,
so that Tilapia grown there include a larger proportion of saleable fish.
Schuster (1952) describes the first appearance of this East African fish
in Javanese waters in 1939, and by the end of World War I1 it was found
t o be firmly established in the Javanese fishponds. It proved a blessing
in those distressful days when the customary cultivation of Chanos was
almost at a standstill. Because there could be no maintenance of the
pond systems during the war, they had largely reverted to the appear-
C. F. HICKLING
Blanco and Acosta (1958) say that the supplementary foods for grey
mullet in the small subsistence ponds on Luzon consist of boiled
" camote )', rice bran, and corn meal, on which the fish grow fast. I n
the Russian limans, the overwintering grey mullet are fed with bloodworms, Daphnia, etc. and in Israel, where the grey mullet are grown
in ponds (in this case, fresh water or very slightly brackish water) in
company with common carp and species of Tilapia, they share with
these other fish the supplementary foods such as oilcakes and grains
which are given on a large scale t o achieve the very high rates of fish
production now customary in Israel. I n Japan, where grey mullets are
grown together with carp or eels, they share the supplementary foods
given to these other fishes, but probably feed mainly on the residues
and faeces which fall to the pond bottom (Asia Kyokai, 1957).
With the intensive rearing of the yellowtail and the Kuruma prawn
in Japan, the whole of the food supplied is supplementary food, since
the fish and prawns being cultivated are far too densely stocked for
natural foods to play any part in their growth. Success must depend
on finding a reliable source of food a t a price, delivered and dispensed
to the fish, which will enable the finished fish to be sold at a profit. I n
Taiwan, I was told that suitable trash fish could be bought in the market
for $2 per Ib, that the conversion rate when fed t o eels was 13 to 1, and
that the eels sold a t the luxury price of $80 per lb. At such prices,
there is a margin of profit, especially as the ponds also contain fish, such
as grey mullet, which feed on the food residues, and add to earnings
without adding to the cost.
VI. MANAGEMENT OF BRACKISH-WATER FISHPONDS
A. Tilapia
Tilapia, is the only fish cultivated in brackish-water fishponds
which will breed naturally there. I n fresh water it is a disappointing
subject for fish culture because in captivity it runts down to a small
and commercially valueless size. Various stratagems have to be
applied to avoid this runting and get marketable fish (Hickling, 1963).
However, in brackish water, maturity seems to be delayed somewhat,
so that Tilapia grown there include a larger proportion of saleable fish.
Schuster (1952) describes the first appearance of this East African fish
in Javanese waters in 1939, and by the end of World War I1 it was found
t o be firmly established in the Javanese fishponds. It proved a blessing
in those distressful days when the customary cultivation of Chanos was
almost at a standstill. Because there could be no maintenance of the
pond systems during the war, they had largely reverted to the appear-