ESTUARINE FISH FARMING
153
Chanos, the young soon seek shallow and less saline water, and generally
tend to congregate where a stream of less saline or fresh water enters
the sea. It is in such places that the fry are caught commercially.
During their growth they can acclimatize completely to fresh water.
As an extreme case, specimens were caught at the Dennison Dam on
the Red River in Texas, 500 miles upstream from the sea at the mouth
of the Mississippi (Riggs, 1957). They enter many fresh-water lakes
and rivers, and have been successfully transferred t o the Sea of Galilee.
In Israel, they are cultivated with carp and Tilapia in fresh-water fish
farms, and have become an important farm fish there.
But not all grey mullets have this breeding pattern. The whereabouts of the breeding grounds of Crenimugil labrosus (Risso), the
commonest English grey mullet, are still unknown, though in April,
1969, a newly-spawned female still releasing a few eggs on pressure
of the abdomen, was caught in the Isles of Scilly. One species of grey
mullet, at first thought to be Mugil cephalus but now believed to be a
different species, has been found spawning in the estuary of the Yung
San River in Korea (Yang and Kim, 1962). The eggs of the grey mullet
Liza macrolepis were found abundantly in the stomachs of the predatory fish Ambassis at the entrance to the Chilka Lake on the east coast
of India (Natarajan and Patnaik, 1967).
Eels are cultivated in Japan and Taiwan (Anguilla japonica) and
in the Mediterranean ( A . anguilla). I n both areas the young are caught
as elvers or as young fish, several centimetres long. The astonishing
life-history of these fish is well enough known, thanks t o Johs Schmidt.
The elvers ascend the estuaries and rivers in great numbers, overcoming
all obstacles. I n the estuary of the River Severn, in Gloucestershire,
England, there is a fishery for the freshly ascending elvers, which are
eaten as a delicacy, and there used to be a fishery €or live elvers that
were theii exported to Germany to stock the eastern fresh waters,
which did not receive enough young eels naturally via the Baltic. The
elvers acclimatize very easily to fresh water, and withstand a low
oxygen tension, as also do the adults.
Salmon and sea-trout acclimatize themselves to sea water on their
downstream migration as smolts or kelts, and in the reverse direction
they spend enough time in the estuaries to acclimatize to fresh water
before ascending the rivers. But the brothers Vik showed how they
could be artificially acclimatized to fresh water from sea water and the
reverse. The writer has amused himself by having in his cubicle two
aquaria, one containing grey mullet, a marine fish. in tap water, and
the other containing rainbow trout, a fresh-water fish, in sea water.
According to Frost (1 968) the acclimatization of rainbow trout to sea
153
Chanos, the young soon seek shallow and less saline water, and generally
tend to congregate where a stream of less saline or fresh water enters
the sea. It is in such places that the fry are caught commercially.
During their growth they can acclimatize completely to fresh water.
As an extreme case, specimens were caught at the Dennison Dam on
the Red River in Texas, 500 miles upstream from the sea at the mouth
of the Mississippi (Riggs, 1957). They enter many fresh-water lakes
and rivers, and have been successfully transferred t o the Sea of Galilee.
In Israel, they are cultivated with carp and Tilapia in fresh-water fish
farms, and have become an important farm fish there.
But not all grey mullets have this breeding pattern. The whereabouts of the breeding grounds of Crenimugil labrosus (Risso), the
commonest English grey mullet, are still unknown, though in April,
1969, a newly-spawned female still releasing a few eggs on pressure
of the abdomen, was caught in the Isles of Scilly. One species of grey
mullet, at first thought to be Mugil cephalus but now believed to be a
different species, has been found spawning in the estuary of the Yung
San River in Korea (Yang and Kim, 1962). The eggs of the grey mullet
Liza macrolepis were found abundantly in the stomachs of the predatory fish Ambassis at the entrance to the Chilka Lake on the east coast
of India (Natarajan and Patnaik, 1967).
Eels are cultivated in Japan and Taiwan (Anguilla japonica) and
in the Mediterranean ( A . anguilla). I n both areas the young are caught
as elvers or as young fish, several centimetres long. The astonishing
life-history of these fish is well enough known, thanks t o Johs Schmidt.
The elvers ascend the estuaries and rivers in great numbers, overcoming
all obstacles. I n the estuary of the River Severn, in Gloucestershire,
England, there is a fishery for the freshly ascending elvers, which are
eaten as a delicacy, and there used to be a fishery €or live elvers that
were theii exported to Germany to stock the eastern fresh waters,
which did not receive enough young eels naturally via the Baltic. The
elvers acclimatize very easily to fresh water, and withstand a low
oxygen tension, as also do the adults.
Salmon and sea-trout acclimatize themselves to sea water on their
downstream migration as smolts or kelts, and in the reverse direction
they spend enough time in the estuaries to acclimatize to fresh water
before ascending the rivers. But the brothers Vik showed how they
could be artificially acclimatized to fresh water from sea water and the
reverse. The writer has amused himself by having in his cubicle two
aquaria, one containing grey mullet, a marine fish. in tap water, and
the other containing rainbow trout, a fresh-water fish, in sea water.
According to Frost (1 968) the acclimatization of rainbow trout to sea