13. EUPHAUSIIDS IN THE MARINE ECONOMY
389
proposition. The euphausiids were supplied as bait and as additional
food in the farming of rainbow trout and salmon. According to Nemoto
(1968a) Euphausia pacifica is used in Japan to feed rainbow trout and as
fertilizer for agricultural land. These kind of fisheries can only be
carried out in fjord regions where deep water, required by the adult
euphausiids, is present close to the shore. The use of light lures fixed to
a floating buoy in regions of weak surface currents might attract dense
swarms of euphausiids that could be harvested by a net which formed
a ring round the swarm and closed underneath it. Such " ring nets "
might also be worked from boats in the Antarctic to obtain maximum
catches of surface swarms of E . superba.
A series of studies-Burukovskiy
and Yarogov (1967), Sedov
(1967), Burukovskiy (1967), Il'ichev (1967), Stasenko (1967), and
Osochenko (1967)-have been made by Russian expeditions on the
suitability and methods of harvesting Euphausia superba in the
Antarctic. The surface swarms were most commonly present in the
areas of the Scotia Sea where the Weddell Sea waters approach closely
to the warmer waters of the West Wind Drift. Commercial concentrations of krill appear to be confined to the upper 50 m layer but the
densest concentrations occur in the upper 1 0 m layer. The swarms
occur most commonly in the latter half of the summer and in the early
autumn in surface waters of temperature between 1-5 and 1.9"C.
Preliminary investigations of methods of processing krill for animal
foodstuffs and of preparing canned foodstuffs were made but the rate of
spoilage is high and all processing had to be done within 48 hr of
catching the animals. Experiments using krill as feed for domestic
animals gave encouraging results. The expeditions also tried various
methods of catching the krill (Stasenko, 1967)-mid-water trawl, a
side-trawl with a fish pump, the uses of artificial coloured lights as
lures, and preliminary experiments on the possible reactions of euphausiids to electrical fishing methods. The 31 m mid-water trawl and the
side-trawl were both effective but losses of euphausiids through the
35-40 mm meshes were experienced. The experiments with artificial
coloured lights, red lights being the best, suggested that freely drifting
sets of light buoys might be dropped by the parent ship which would
then return at a later time and net the krill accumulated around each
buoy.
Jackson (1954) has reviewed the economic aspects of harvesting
plankton in general and some of his remarks are pertinent to the
harvesting of krill. He concludes that none of the proposed methods of
harvesting plankton are economic because the probable economic price
would have to be in the region of 22 000 to g3 000 per dry ton plankton.
389
proposition. The euphausiids were supplied as bait and as additional
food in the farming of rainbow trout and salmon. According to Nemoto
(1968a) Euphausia pacifica is used in Japan to feed rainbow trout and as
fertilizer for agricultural land. These kind of fisheries can only be
carried out in fjord regions where deep water, required by the adult
euphausiids, is present close to the shore. The use of light lures fixed to
a floating buoy in regions of weak surface currents might attract dense
swarms of euphausiids that could be harvested by a net which formed
a ring round the swarm and closed underneath it. Such " ring nets "
might also be worked from boats in the Antarctic to obtain maximum
catches of surface swarms of E . superba.
A series of studies-Burukovskiy
and Yarogov (1967), Sedov
(1967), Burukovskiy (1967), Il'ichev (1967), Stasenko (1967), and
Osochenko (1967)-have been made by Russian expeditions on the
suitability and methods of harvesting Euphausia superba in the
Antarctic. The surface swarms were most commonly present in the
areas of the Scotia Sea where the Weddell Sea waters approach closely
to the warmer waters of the West Wind Drift. Commercial concentrations of krill appear to be confined to the upper 50 m layer but the
densest concentrations occur in the upper 1 0 m layer. The swarms
occur most commonly in the latter half of the summer and in the early
autumn in surface waters of temperature between 1-5 and 1.9"C.
Preliminary investigations of methods of processing krill for animal
foodstuffs and of preparing canned foodstuffs were made but the rate of
spoilage is high and all processing had to be done within 48 hr of
catching the animals. Experiments using krill as feed for domestic
animals gave encouraging results. The expeditions also tried various
methods of catching the krill (Stasenko, 1967)-mid-water trawl, a
side-trawl with a fish pump, the uses of artificial coloured lights as
lures, and preliminary experiments on the possible reactions of euphausiids to electrical fishing methods. The 31 m mid-water trawl and the
side-trawl were both effective but losses of euphausiids through the
35-40 mm meshes were experienced. The experiments with artificial
coloured lights, red lights being the best, suggested that freely drifting
sets of light buoys might be dropped by the parent ship which would
then return at a later time and net the krill accumulated around each
buoy.
Jackson (1954) has reviewed the economic aspects of harvesting
plankton in general and some of his remarks are pertinent to the
harvesting of krill. He concludes that none of the proposed methods of
harvesting plankton are economic because the probable economic price
would have to be in the region of 22 000 to g3 000 per dry ton plankton.