196
C . F. HICKLING
tolerated by Chanos. Growth ceases in winter and the Chanos have t o
be overwintered in specially protected ponds. Because of this, the
technique in Taiwan differs from that in Java and the Philippines,
where there is no winter, and where the growth of the fish is continuous
all year round. But in spite of there being only eight growing months in
the year in Taiwan, the rate of production is high for three reasons.
Firstly, care is taken to ensure a good algal pasture throughout the
growing period, secondly, the fish are given a supply of supplementary
food, especially if there is a threat of overgrazing of the algal pasture,
and thirdly, the method of mixed stocking.
The overwintering of Chanos has been described. To get the best
results when the fertilized ponds are stocked in April, when the water
temperature rises above 22OC, the rate of stocking with overwintered
fingerlings is 4 000-5 000 fish of 10-100 g per hectare. I n addition
5 000-8 000 new fry of the year are stocked over the period May t o
September as and when they become available. The larger overwintered
fish will grow fast to give a crop in July of about 1 300 kglhectare, at the
time of year when prices are high. They are selectively fished for sale as
they grow, so that increased space and food become available to speed
the growth of the remaining smaller fish. The best-grown of the new fry
of the year will be of marketable size by autumn, and can add 800 kg/
hectare of fish of an average weight of 200 g . Thus, the total weight
of Chanos for sale will be about 2 100 kglhectare, plus enough fry of the
year, not large enough to be marketable, to provide the stock to restart the next year's production.
Lin sums up as follows: with an average water temperature of
25°C in April, 31OC in May to August, and 27OC from September to
early November, the overwintered fingerlings, stocked in the rearing
ponds in April, will grow to a weight of 350g in 50-70 days at a
survival rate of 95%. The smaller overwintered fingerlings will grow
t o 300-450 g in 90-120 days, also with a 95% survival. The new fry
of the year stocked in May and June will grow to 200 g or more in
120-150 days, with an 85% survival; and of the late new fry of the
season, stocked June, one half can be expected to grow to 150-200 g
by October and November at a survival rate of 80%. The remainder
of the years' fry go t o the overwintering ponds, where, a t weights from
10-lOOg, they are confined in small ponds in very congested conditions for four months, during which, in spite of careful feeding, they
may lose 10-17~0 of their weight, and have a survival rate of 60-95y0
depending on the condition of the fish and the oxygen supply.
Tang (1967) adapted these methods to the Philippines, where there
is no winter cessation of growth, so that Tang allows for a daily rate
C . F. HICKLING
tolerated by Chanos. Growth ceases in winter and the Chanos have t o
be overwintered in specially protected ponds. Because of this, the
technique in Taiwan differs from that in Java and the Philippines,
where there is no winter, and where the growth of the fish is continuous
all year round. But in spite of there being only eight growing months in
the year in Taiwan, the rate of production is high for three reasons.
Firstly, care is taken to ensure a good algal pasture throughout the
growing period, secondly, the fish are given a supply of supplementary
food, especially if there is a threat of overgrazing of the algal pasture,
and thirdly, the method of mixed stocking.
The overwintering of Chanos has been described. To get the best
results when the fertilized ponds are stocked in April, when the water
temperature rises above 22OC, the rate of stocking with overwintered
fingerlings is 4 000-5 000 fish of 10-100 g per hectare. I n addition
5 000-8 000 new fry of the year are stocked over the period May t o
September as and when they become available. The larger overwintered
fish will grow fast to give a crop in July of about 1 300 kglhectare, at the
time of year when prices are high. They are selectively fished for sale as
they grow, so that increased space and food become available to speed
the growth of the remaining smaller fish. The best-grown of the new fry
of the year will be of marketable size by autumn, and can add 800 kg/
hectare of fish of an average weight of 200 g . Thus, the total weight
of Chanos for sale will be about 2 100 kglhectare, plus enough fry of the
year, not large enough to be marketable, to provide the stock to restart the next year's production.
Lin sums up as follows: with an average water temperature of
25°C in April, 31OC in May to August, and 27OC from September to
early November, the overwintered fingerlings, stocked in the rearing
ponds in April, will grow to a weight of 350g in 50-70 days at a
survival rate of 95%. The smaller overwintered fingerlings will grow
t o 300-450 g in 90-120 days, also with a 95% survival. The new fry
of the year stocked in May and June will grow to 200 g or more in
120-150 days, with an 85% survival; and of the late new fry of the
season, stocked June, one half can be expected to grow to 150-200 g
by October and November at a survival rate of 80%. The remainder
of the years' fry go t o the overwintering ponds, where, a t weights from
10-lOOg, they are confined in small ponds in very congested conditions for four months, during which, in spite of careful feeding, they
may lose 10-17~0 of their weight, and have a survival rate of 60-95y0
depending on the condition of the fish and the oxygen supply.
Tang (1967) adapted these methods to the Philippines, where there
is no winter cessation of growth, so that Tang allows for a daily rate