ESTUARINE FISH FARMINU
149
111. THE SPECIES CULTURED
A. Selection of organisms by salinity
As Vatova (1962) said of the Adriatic lagoons, from the moment
they enter the ponds, the organisms are selected for those forms which
can stand the rigorous environment, not only of extreme and rapid
changes of salinity, but also of temperature (0-31°C in Italy, 8-37°C
in Taiwan) and dissolved oxygen (49-212% saturation in Italy). The
fauna so selected are few in species but rich in individuals, as would
be expected from fertile ponds. The fish which enter such ponds are
either species which make true anadromous migrations, staying for
one or more years (eels and to some extent grey mullets, sparids, and
flounders) or temporary dwellers which enter in spring and summer
for feeding, attracted by the warm water and plentiful food. All such
fish must be euryhaline, and they are predominantly marine fish.
Beadle has pointed out that most fresh-water animals are unable
to maintain a blood hypotonic to the external water and, with few
exceptions, they ara restricted to salinities below lo%,. d’Ancona
expresses the same thing by saying that the fish fauna of brackishwater is chiefly of marine origin, since many marine fish can support
the dilution of sea water, while few fresh water species can tolerate an
increase in salinity.
Doroshev (1963) tested this in the brackish-waters of the Sea of
Azov and the Aral Sea, using two species of fresh-water herbivorous
fish, native to the rivers flowing eastward to the Pacific. There are
vast stocks of vegetable food in these two seas which are used little or
not at all because the fish fauna of those waters do not include herbivorous fish. I n the hope that some of the unused plant production
might support a fishery for herbivorous fish, Doroshev tested the
salinity tolerance of two large and valuable members of the carp
family-the Grass Carp or White Amur, (Ctenopharyngodon idella Val.)
and the Silver Carp or- White Tolstolobik (Hyiophthalmichthys molitrix
Val.).
Doroshev found that the Grass Carp could survive without ill
effects six weeks to two months in Sea of Azov water with salinities up
to 9%,, if gradually acclimatized. I n Aral Sea water, grass carp would
tolerate even 12%, after acclimatization. The silver carp (a phytoplankton feeder) would survive in Sea of Azov water of up to 7 . ~ 5 % ~
after
acclimatization, and in Aral Sea water up to 10-5%,. They did best
when slowly acclimatized to the change. Above these salinities, a
breakdown of salt metabolism, illness, cessation of growth, and a high
mortality were observed. Doroshev concluded that the salinity of the
A.P.H.-8
n
149
111. THE SPECIES CULTURED
A. Selection of organisms by salinity
As Vatova (1962) said of the Adriatic lagoons, from the moment
they enter the ponds, the organisms are selected for those forms which
can stand the rigorous environment, not only of extreme and rapid
changes of salinity, but also of temperature (0-31°C in Italy, 8-37°C
in Taiwan) and dissolved oxygen (49-212% saturation in Italy). The
fauna so selected are few in species but rich in individuals, as would
be expected from fertile ponds. The fish which enter such ponds are
either species which make true anadromous migrations, staying for
one or more years (eels and to some extent grey mullets, sparids, and
flounders) or temporary dwellers which enter in spring and summer
for feeding, attracted by the warm water and plentiful food. All such
fish must be euryhaline, and they are predominantly marine fish.
Beadle has pointed out that most fresh-water animals are unable
to maintain a blood hypotonic to the external water and, with few
exceptions, they ara restricted to salinities below lo%,. d’Ancona
expresses the same thing by saying that the fish fauna of brackishwater is chiefly of marine origin, since many marine fish can support
the dilution of sea water, while few fresh water species can tolerate an
increase in salinity.
Doroshev (1963) tested this in the brackish-waters of the Sea of
Azov and the Aral Sea, using two species of fresh-water herbivorous
fish, native to the rivers flowing eastward to the Pacific. There are
vast stocks of vegetable food in these two seas which are used little or
not at all because the fish fauna of those waters do not include herbivorous fish. I n the hope that some of the unused plant production
might support a fishery for herbivorous fish, Doroshev tested the
salinity tolerance of two large and valuable members of the carp
family-the Grass Carp or White Amur, (Ctenopharyngodon idella Val.)
and the Silver Carp or- White Tolstolobik (Hyiophthalmichthys molitrix
Val.).
Doroshev found that the Grass Carp could survive without ill
effects six weeks to two months in Sea of Azov water with salinities up
to 9%,, if gradually acclimatized. I n Aral Sea water, grass carp would
tolerate even 12%, after acclimatization. The silver carp (a phytoplankton feeder) would survive in Sea of Azov water of up to 7 . ~ 5 % ~
after
acclimatization, and in Aral Sea water up to 10-5%,. They did best
when slowly acclimatized to the change. Above these salinities, a
breakdown of salt metabolism, illness, cessation of growth, and a high
mortality were observed. Doroshev concluded that the salinity of the
A.P.H.-8
n