REARING OF BIVALVE MOLLUSKS
7
Ultraviolet treatment of sea water for purification of shellhh has
been described by several workers in Japan (Sato, 1964; Satoh, 1960)
and Wood (1961) in England. As is the practice in our laboratory,
Waugh (1958) also used ultraviolet-treated sea water for rearing larvae
of the European oyster, 0. edulig. Several of these authors have
described the equipment used but, because of certain considerations,
we constructed our own units, a description of whioh is offered here.
The ultraviolet water treatment unit consisfs of a 1)-in inside
diameter PVC pipe, 30 in long, threaded at each end for caps (Fig. 2).
A small ring of PVC is cut to fit inside of each end of this pipe and
reamed to act as a spacer for a 26-mm Vycor tube. A squeeze gasket
is wed to make a water-tight seal between the Vycor tube and the end
of the PVC pipe. An inlet tube is located on the side at one end of the
PVC pipe and an outlet tube is located on the opposite side at the other
end. The 33-in-long, slimline ultraviolet tube lays free in the 324411long Vycor tube and extends slightly beyond at each end.
In practice we use two such units connected in a series so that the
water passes the length of both tubes. Since there is only about a
4-in layer of water surrounding the Vycor tube, this apparatus, when
used with filtered sea water, should give practically sterile water at
the rate of flow of about 10 gal per min. With unfiltered sea water
the efficiency is not expecid to be as great, but our experience has
shown that even then the treatment is of considerable help in reducing
mortality of juvenile clams and in preventing fouling by tunicates,
worms and bryozoa.
To condition mollusks for out-of-season spawning it is necessary to
keep them in running sea water at temperatures of 18" to 20°C or
sometimes higher. Warm sea water is also needed for rearing larvae and
juveniles during the cold season. Since the water must not contact
toxic metals, conventional water heaters cannot be used. Therefore, to
heat the water we use a type of heat exchanger (haanoff, 1949). The
sea water is heated as it passes through a coil of lead pipe immersed in
hot fresh water, which fills the tank of a conventional gas water
heater that has had the top removed to permit insertion of the lead
coil (Fig. 3). However, because the thermostatic controls of a conventional water heater are not sufficiently accurate, the gas flame is controlled through a solenoid gas valve by a Minneapolis-Honeywell
thermostat (T415A323XA3). The thermostat-sensing bulb is e n c d
in a lead well in the warm sea water line and maintains the temperature
at 37°C f 0-5"C.
By mixing varied amounts of cold and heated sea water any temperature between that of the unheated water and 37°C can be main-
7
Ultraviolet treatment of sea water for purification of shellhh has
been described by several workers in Japan (Sato, 1964; Satoh, 1960)
and Wood (1961) in England. As is the practice in our laboratory,
Waugh (1958) also used ultraviolet-treated sea water for rearing larvae
of the European oyster, 0. edulig. Several of these authors have
described the equipment used but, because of certain considerations,
we constructed our own units, a description of whioh is offered here.
The ultraviolet water treatment unit consisfs of a 1)-in inside
diameter PVC pipe, 30 in long, threaded at each end for caps (Fig. 2).
A small ring of PVC is cut to fit inside of each end of this pipe and
reamed to act as a spacer for a 26-mm Vycor tube. A squeeze gasket
is wed to make a water-tight seal between the Vycor tube and the end
of the PVC pipe. An inlet tube is located on the side at one end of the
PVC pipe and an outlet tube is located on the opposite side at the other
end. The 33-in-long, slimline ultraviolet tube lays free in the 324411long Vycor tube and extends slightly beyond at each end.
In practice we use two such units connected in a series so that the
water passes the length of both tubes. Since there is only about a
4-in layer of water surrounding the Vycor tube, this apparatus, when
used with filtered sea water, should give practically sterile water at
the rate of flow of about 10 gal per min. With unfiltered sea water
the efficiency is not expecid to be as great, but our experience has
shown that even then the treatment is of considerable help in reducing
mortality of juvenile clams and in preventing fouling by tunicates,
worms and bryozoa.
To condition mollusks for out-of-season spawning it is necessary to
keep them in running sea water at temperatures of 18" to 20°C or
sometimes higher. Warm sea water is also needed for rearing larvae and
juveniles during the cold season. Since the water must not contact
toxic metals, conventional water heaters cannot be used. Therefore, to
heat the water we use a type of heat exchanger (haanoff, 1949). The
sea water is heated as it passes through a coil of lead pipe immersed in
hot fresh water, which fills the tank of a conventional gas water
heater that has had the top removed to permit insertion of the lead
coil (Fig. 3). However, because the thermostatic controls of a conventional water heater are not sufficiently accurate, the gas flame is controlled through a solenoid gas valve by a Minneapolis-Honeywell
thermostat (T415A323XA3). The thermostat-sensing bulb is e n c d
in a lead well in the warm sea water line and maintains the temperature
at 37°C f 0-5"C.
By mixing varied amounts of cold and heated sea water any temperature between that of the unheated water and 37°C can be main-