ESTUARINE FISH FARMING
165
These two fish share the following features, (i) small and toothless
mouth, (ii) shovel-like lower jaw, (iii) absence of all masticating teeth,
(iv) a pharyngeal sieving mechanism, including gill rakers, (v) an
anterior thin-walled stomach for food storage, (vi) a very muscular
bird-like gizzard of rather uncertain function and (vii) a very long
intestine, relatively shorter in juveniles. Several different accounts
have been given of the food and feeding of Chanos and grey mullet but
the food in fact is so similar that Hiatt (1944) could say, of the Hawaiian
fishponds where both fish occur together, that competition for food was
greater than had been supposed. Schuster agrees, but adds that if the
competing grey mullet are of a species which grows to a large size, the
fish farmer has nothing to worry about, since the mullet grow as fast,
as the Chanos and fetch the same price. I n fact, however, the two fish
have different geographical distributions so that competition is
limited. For example, the southern coast of Taiwan is warm enough
for the culture of Chanos, but the west coast is too cold so that grey
mullet are cultivated in the ponds instead, and by the same methods.
There is some difference of opinion about the food of the growing
Chanos. Fish have been found feeding on different materials in the
same pond. There is general agreement that blue-green algae and
diatoms represent a high proportion of the food, and that they are
preferred to green algae. Thus Schuster found that Chanos grown in
a pond with a dense growth of green algae had eaten proportionately
more blue-greens and less green algae than would be expected. Comparing two populations of Chanos, one in a pond well-grown with bluegreens, and one in a green-alga pond, it was found that in the latter 49
out of 66 stomachs were empty, whereas, in the former, only 20 out
of 75 were empty. It would seem that many Chanos would rather go
hungry than feed on green algae. Even so, there was a higher proportion of blue-green than green algae and a much higher proportion of
detritus in the stomachs of Chanos from the green alga pond (Schuster,
1952).
Larger Chanos, however, seem able to flourish on green algae,
especially when it has begun to decay. Even parts of higher plants,
such as the leaves of Ruppia, are eaten, though the statement that
Chanos, transplanted to fresh-water reservoirs in India, controlled the
vegetation, must await confirmation, as the fish has no provision for
masticating higher plants. As Schuster (1952) writes, Chanos is morphologically adapted to consume great quantities of soft and smallgrained food, and to digest it quickly. The same is true of grey mullet.
I n the Philippines, " lumut " or filamentous green algae are considered suitable food for larger Chanos, and are cultivated for the
165
These two fish share the following features, (i) small and toothless
mouth, (ii) shovel-like lower jaw, (iii) absence of all masticating teeth,
(iv) a pharyngeal sieving mechanism, including gill rakers, (v) an
anterior thin-walled stomach for food storage, (vi) a very muscular
bird-like gizzard of rather uncertain function and (vii) a very long
intestine, relatively shorter in juveniles. Several different accounts
have been given of the food and feeding of Chanos and grey mullet but
the food in fact is so similar that Hiatt (1944) could say, of the Hawaiian
fishponds where both fish occur together, that competition for food was
greater than had been supposed. Schuster agrees, but adds that if the
competing grey mullet are of a species which grows to a large size, the
fish farmer has nothing to worry about, since the mullet grow as fast,
as the Chanos and fetch the same price. I n fact, however, the two fish
have different geographical distributions so that competition is
limited. For example, the southern coast of Taiwan is warm enough
for the culture of Chanos, but the west coast is too cold so that grey
mullet are cultivated in the ponds instead, and by the same methods.
There is some difference of opinion about the food of the growing
Chanos. Fish have been found feeding on different materials in the
same pond. There is general agreement that blue-green algae and
diatoms represent a high proportion of the food, and that they are
preferred to green algae. Thus Schuster found that Chanos grown in
a pond with a dense growth of green algae had eaten proportionately
more blue-greens and less green algae than would be expected. Comparing two populations of Chanos, one in a pond well-grown with bluegreens, and one in a green-alga pond, it was found that in the latter 49
out of 66 stomachs were empty, whereas, in the former, only 20 out
of 75 were empty. It would seem that many Chanos would rather go
hungry than feed on green algae. Even so, there was a higher proportion of blue-green than green algae and a much higher proportion of
detritus in the stomachs of Chanos from the green alga pond (Schuster,
1952).
Larger Chanos, however, seem able to flourish on green algae,
especially when it has begun to decay. Even parts of higher plants,
such as the leaves of Ruppia, are eaten, though the statement that
Chanos, transplanted to fresh-water reservoirs in India, controlled the
vegetation, must await confirmation, as the fish has no provision for
masticating higher plants. As Schuster (1952) writes, Chanos is morphologically adapted to consume great quantities of soft and smallgrained food, and to digest it quickly. The same is true of grey mullet.
I n the Philippines, " lumut " or filamentous green algae are considered suitable food for larger Chanos, and are cultivated for the