40
J. E. SHELBOURNE
Bidtrix (1902), Dannevig (1910a) and many other marine fish culturists.
Direct aeration has the effect of driving buoyent eggs into regions of
least water movement, and, unless very gentle indeed, can cause
heavy mortalities among delicate, newly-hatched larvae. Oxygen
release by Enteromorpha and diffusion from the atmosphere was
sufficient to meet larval demands during the pelagic phase; after
metamorphosis, direct aeration was of definite value in deep, wellpopulated tanks.
3. Larval food production and the feeding technique
The efforts of early pioneers to rear marine fish were hampered
by inadequate and unsuitable larval food supplies. Rollefsen (1939)
first demonstrated the value of Artemia salina (brine shrimp) nauplii
as a food source. The brine shrimp is not indigenous to Britain, but
its eggs can be imported in bulk from America, at a reasonable price.
They hatch within 42 h at temperatures between 20" and 23"C, in
normal sea water, and can readily be cultured to the metanaupliar and
adult stages in the laboratory, for feeding to larger fish. There is one
drawback-the nauplius is rather large for " first-feeding " plaice
larvae. The nrtuplii of BaEanus balun&
are much smaller and it
wm our early practice to offer these during the first week or so of
feeding, until larval survivors are large enough to live and grow on
Artemia alone. Barnacle nauplii are easily obtained in spring by
stripping adults from intertidal surfaces and covering them with sea
water in glass tanks. The nauplii are immediately released and, being
strongly phototactic, can be concentrated by unidirectional light.
The use of Balanw as a first food was a purely empirical measureits praotical value has not yet been proved beyond doubt.
In 1967-69 the feeding technique was as follows: About 5 days
after the first egg hatched in each tank, a small ration of washed
barnacle nauplii was offered. Daily increments were maintained for
3 days before adding the first Artemia nauplii, which were hatched in
beakers in a water bath, and separated from egg shells and unhatched
eggs by exploiting their phototactic behaviour. High Artmia concentrations were gradually built up and Balanw increments tapered off.
Rations of Artemia nauplii were subsequently offered every
morning, in quantities suffioient to maintain a residual food population
after 24 h of larval feeding. Following metamorphosis, the diet was
varied with the oligochaetes Enchytraew albidw and E. bueholzii, both of
which are r e d l y cultured on damp pent enriched with pre-cooked meal.
Dead and partly digested Artemia nauplii form a pink carpet of autolysed tiesue an the bottoms of tanks, and should be regularly removed.
J. E. SHELBOURNE
Bidtrix (1902), Dannevig (1910a) and many other marine fish culturists.
Direct aeration has the effect of driving buoyent eggs into regions of
least water movement, and, unless very gentle indeed, can cause
heavy mortalities among delicate, newly-hatched larvae. Oxygen
release by Enteromorpha and diffusion from the atmosphere was
sufficient to meet larval demands during the pelagic phase; after
metamorphosis, direct aeration was of definite value in deep, wellpopulated tanks.
3. Larval food production and the feeding technique
The efforts of early pioneers to rear marine fish were hampered
by inadequate and unsuitable larval food supplies. Rollefsen (1939)
first demonstrated the value of Artemia salina (brine shrimp) nauplii
as a food source. The brine shrimp is not indigenous to Britain, but
its eggs can be imported in bulk from America, at a reasonable price.
They hatch within 42 h at temperatures between 20" and 23"C, in
normal sea water, and can readily be cultured to the metanaupliar and
adult stages in the laboratory, for feeding to larger fish. There is one
drawback-the nauplius is rather large for " first-feeding " plaice
larvae. The nrtuplii of BaEanus balun&
are much smaller and it
wm our early practice to offer these during the first week or so of
feeding, until larval survivors are large enough to live and grow on
Artemia alone. Barnacle nauplii are easily obtained in spring by
stripping adults from intertidal surfaces and covering them with sea
water in glass tanks. The nauplii are immediately released and, being
strongly phototactic, can be concentrated by unidirectional light.
The use of Balanw as a first food was a purely empirical measureits praotical value has not yet been proved beyond doubt.
In 1967-69 the feeding technique was as follows: About 5 days
after the first egg hatched in each tank, a small ration of washed
barnacle nauplii was offered. Daily increments were maintained for
3 days before adding the first Artemia nauplii, which were hatched in
beakers in a water bath, and separated from egg shells and unhatched
eggs by exploiting their phototactic behaviour. High Artmia concentrations were gradually built up and Balanw increments tapered off.
Rations of Artemia nauplii were subsequently offered every
morning, in quantities suffioient to maintain a residual food population
after 24 h of larval feeding. Following metamorphosis, the diet was
varied with the oligochaetes Enchytraew albidw and E. bueholzii, both of
which are r e d l y cultured on damp pent enriched with pre-cooked meal.
Dead and partly digested Artemia nauplii form a pink carpet of autolysed tiesue an the bottoms of tanks, and should be regularly removed.