13. EUPHAUSIIDS IN THE MARINE ECONOMY
375
Some of these species, however, are much more important than
others because species like Thysanoessa inermis or Euphausia superba
ar0 important over a wide geographical range while a species such as
Nyctiphanes australis is only important in its rather restricted area of
occurrence off southeastern Australia. Consequently, the following can
be listed as of primary importance :
Meganyctiphanes norvegica; Euphausia superba, E. pucijica, E.
crystallorophias; Thysanoessa inermis, T . raschii, T . macrura,
T . 1ongipeslT. inspinata.
A second group consists of species of importance in relatively
restricted geographical areas and/or at certain seasons to certain
predators :
Nyctiphanes couchii, N . capensis, N . australis; Pseudeuphausia
latifrons; Euphausia vallentini, E. similis; Thysanoessa spinifera.
A third group contains species that are occasionally important as
Euphausia recurva, E. lucens, E. hemigi66a) E. spinifera;
food in certain areas at certain times :
Thysanoessa gregaria; NematosceEis megalops.
What is the biomass of euphausiids present in different sea areas!
This is an extremely difficult question to answer because of the sampling
problems involved and also because these animals swarm a t certain
times of the year and these aggregations disperse a t other times.
Zelikman (1 958a) estimated the biomass of euphausiids, mainly
Thysunoessa inermis and T . raschii, in the upper layers of the Barents
Sea to be between 70 and 114 mg per cubic metre ; this compares with
300 mg and represents a density of approximately one euphausiid per
cubic metre. Euphausiid eggs and larvae contributed significantly to
the plankton biomass off western and northwestern Norway and in the
Barents Sea in the spring and early summer (Wiborg, 1954; Zelikman,
1958a) and the same is true in the Clyde Sea area where they can
represent as much as l0-20% of the volume of the spring zooplankton.
Jespersen (1 924), studying the quantitative distribution of the plankton
throughout the Mediterranean, concluded that the density of Meganycticonsiderably affects the total quantity of macroplankton ". This was
further borne out by his later data (Jespersen, 1935) from the world
cruise of the " Dana " ; euphausiids represented substantia1 portions of
the total volumes of plankton caught in areas such as the Azores to Cape
a mazimm fipring plankton (ezduding euphau&%$ bioiomam of about
phanes wruegica pxeaent '' . . . in %seat p a x t ~ of tkc Me&te..xane.an
13
A.?d.B.-7
375
Some of these species, however, are much more important than
others because species like Thysanoessa inermis or Euphausia superba
ar0 important over a wide geographical range while a species such as
Nyctiphanes australis is only important in its rather restricted area of
occurrence off southeastern Australia. Consequently, the following can
be listed as of primary importance :
Meganyctiphanes norvegica; Euphausia superba, E. pucijica, E.
crystallorophias; Thysanoessa inermis, T . raschii, T . macrura,
T . 1ongipeslT. inspinata.
A second group consists of species of importance in relatively
restricted geographical areas and/or at certain seasons to certain
predators :
Nyctiphanes couchii, N . capensis, N . australis; Pseudeuphausia
latifrons; Euphausia vallentini, E. similis; Thysanoessa spinifera.
A third group contains species that are occasionally important as
Euphausia recurva, E. lucens, E. hemigi66a) E. spinifera;
food in certain areas at certain times :
Thysanoessa gregaria; NematosceEis megalops.
What is the biomass of euphausiids present in different sea areas!
This is an extremely difficult question to answer because of the sampling
problems involved and also because these animals swarm a t certain
times of the year and these aggregations disperse a t other times.
Zelikman (1 958a) estimated the biomass of euphausiids, mainly
Thysunoessa inermis and T . raschii, in the upper layers of the Barents
Sea to be between 70 and 114 mg per cubic metre ; this compares with
300 mg and represents a density of approximately one euphausiid per
cubic metre. Euphausiid eggs and larvae contributed significantly to
the plankton biomass off western and northwestern Norway and in the
Barents Sea in the spring and early summer (Wiborg, 1954; Zelikman,
1958a) and the same is true in the Clyde Sea area where they can
represent as much as l0-20% of the volume of the spring zooplankton.
Jespersen (1 924), studying the quantitative distribution of the plankton
throughout the Mediterranean, concluded that the density of Meganycticonsiderably affects the total quantity of macroplankton ". This was
further borne out by his later data (Jespersen, 1935) from the world
cruise of the " Dana " ; euphausiids represented substantia1 portions of
the total volumes of plankton caught in areas such as the Azores to Cape
a mazimm fipring plankton (ezduding euphau&%$ bioiomam of about
phanes wruegica pxeaent '' . . . in %seat p a x t ~ of tkc Me&te..xane.an
13
A.?d.B.-7