376
THE BIOLOGY OF EUPHAUSIIDS
Finisterre, in the regions of the Straits of Gibraltar, the southern part
of the East China Sea, and off southern Ceylon. Curl (1962a) on the
other hand, examining the plankton of the continental shelf waters of
the western Atlantic south of New York, found that euphausiids only
represented more than 25% of the total volume of plankton at a few
stations and Grice and Hart (1962) showed that euphausiids were not
important in the sea area between New York and Bermuda, representing
only about 5% by volume of the plankton samples. Bigelow and Sears
(1939) reviewed previous estimations of plankton volumes of the North
Atlantic and found that they ranged between 0.01 and 1.9 ml/m3
dependent upon the geographical location and season. They found
that a t certain of their stations euphausiids constituted as much
as 20-30y0 of the total volume of zooplankton, and occasionally more,
but in general represented only a few per cent by volume of the whole
sample.
Ponomareva (1966) attempts to calculate the standing stocks of
euphausiids in the Pacific Ocean and suggests that there are about
28 million tons of euphausiids distributed throughout all the oceans.
Taking the total area of the oceans from Table XXXIII, this weight
of euphausiids represents about 0.08 g under 1 m2 of ocean. This is a
very conservative estimate and not borne out by her data on the
numbers of euphausiids per 1 0 0 0 m3 of water in the upper 100 m
layer of the Pacific Ocean (Fig. 133). As can be seen in this figure, the
average density of euphausiids must lie between 100 and 500 animals
per 1 000 m3. There is a wide range of size and weight between different
species of euphausiids (Fig. 110) but if a conservative figure of 0.05 g
is taken as the body weight of one individual then a total weight of
0.5-2-5 g is present under 1 m2 of the surface layers of the Pacific.
This is a very conservative estimate for the water column and Brinton
(quoted by Lasker, 1966) suggests that the biomass of Euphausiapacifica
alone, throughout its geographical range, is about 1 g per square metre.
What probably emerges more accurately from Ponomareva's work, and
that of other investigators, is that the biomass of euphausiids is greatest
in the North Pacific, North Atlantic and Antarctic Oceans and least in
tropical and subtropical areas. This is substantiated, for plankton in
general, by Foxton (1956) who advancesrather tentative figures for standing crops of zooplankton in different latitudinal areas. The ratio of standing crops tropic : subtropic : subantarctic : Antarctic is roughly 1 : 1.3 :
2.7 : 3.3. The sampling method used by Foxton did not sample euphausiids efficiently because he used the " Discovery ) ) pattern 70 cm vertical
closing net (N70V) and not the larger 1 m net. He instances one haul in
the Weddell Drift when a horizontal tow with a 1 m net caught
THE BIOLOGY OF EUPHAUSIIDS
Finisterre, in the regions of the Straits of Gibraltar, the southern part
of the East China Sea, and off southern Ceylon. Curl (1962a) on the
other hand, examining the plankton of the continental shelf waters of
the western Atlantic south of New York, found that euphausiids only
represented more than 25% of the total volume of plankton at a few
stations and Grice and Hart (1962) showed that euphausiids were not
important in the sea area between New York and Bermuda, representing
only about 5% by volume of the plankton samples. Bigelow and Sears
(1939) reviewed previous estimations of plankton volumes of the North
Atlantic and found that they ranged between 0.01 and 1.9 ml/m3
dependent upon the geographical location and season. They found
that a t certain of their stations euphausiids constituted as much
as 20-30y0 of the total volume of zooplankton, and occasionally more,
but in general represented only a few per cent by volume of the whole
sample.
Ponomareva (1966) attempts to calculate the standing stocks of
euphausiids in the Pacific Ocean and suggests that there are about
28 million tons of euphausiids distributed throughout all the oceans.
Taking the total area of the oceans from Table XXXIII, this weight
of euphausiids represents about 0.08 g under 1 m2 of ocean. This is a
very conservative estimate and not borne out by her data on the
numbers of euphausiids per 1 0 0 0 m3 of water in the upper 100 m
layer of the Pacific Ocean (Fig. 133). As can be seen in this figure, the
average density of euphausiids must lie between 100 and 500 animals
per 1 000 m3. There is a wide range of size and weight between different
species of euphausiids (Fig. 110) but if a conservative figure of 0.05 g
is taken as the body weight of one individual then a total weight of
0.5-2-5 g is present under 1 m2 of the surface layers of the Pacific.
This is a very conservative estimate for the water column and Brinton
(quoted by Lasker, 1966) suggests that the biomass of Euphausiapacifica
alone, throughout its geographical range, is about 1 g per square metre.
What probably emerges more accurately from Ponomareva's work, and
that of other investigators, is that the biomass of euphausiids is greatest
in the North Pacific, North Atlantic and Antarctic Oceans and least in
tropical and subtropical areas. This is substantiated, for plankton in
general, by Foxton (1956) who advancesrather tentative figures for standing crops of zooplankton in different latitudinal areas. The ratio of standing crops tropic : subtropic : subantarctic : Antarctic is roughly 1 : 1.3 :
2.7 : 3.3. The sampling method used by Foxton did not sample euphausiids efficiently because he used the " Discovery ) ) pattern 70 cm vertical
closing net (N70V) and not the larger 1 m net. He instances one haul in
the Weddell Drift when a horizontal tow with a 1 m net caught