2
THE BIOLOGY O F EUPHAUSIIDS
animals. Marr (1962), in his magnificent monograph on the main
Antarctic species, Euphausia superba Dana, describes the extent of the
predation of the baleen whales on this organism. Hickling (1927) stressed
the importance of Meganyctiphanes norvegica to the hake fishery in the
southern Irish Sea and Poulsen (1926) showed that this crustacean was
essential to the fisheries of Skagerrak, especially for herring and mackerel.
Both M . norvegica and Thysanoessa raschii are important, in certain
coastal areas, to herring and mackerel. I n their account of whaling and
fishing in the North Atlantic, Hjort and Ruud (1929) repeatedly mention the importance of euphausiids, especially Meganyctiphanes
norvegica and Thysanoessa inermis as whale food and in the economy of
northern seas. The pilchard and mackerel shoals in the English Channel
(Lebour, 1924) feed to a large extent on Nyctiphanes couchii (Bell).
Other euphausiids are important in the Pacific Ocean mainly as food
of whales. Euphausia paciJica Hansen around Japan, Thysanoessa
inermis and T . longipes Brandt in the northern Pacific and T . macrura
G. 0. Sars and Euphausia crystallorophias Holt and Tattersall, along
with E . superba, constitute the food of the Antarctic whales.
It is not their numbers alone that render euphausiids so important
in the food chains of higher marine animals. What is so valuable to
their predators is their habit of living in great concentrations or swarms,
that migrate vertically as well as horizontally in response to light,
food, temperature, salinity, and many other factors of their environment. This swarming habit is particularly suitable for the feeding
mechanism of the baleen whales whose feeding has already been
described in the account by Scoresby. The great blue whale, the
largest animal ever to have existed, lives exclusively on euphausiids and
Collett (1911-12) has told how it swims back and forth in a swarm of
them with its mouth wide open, often turning on its side or back to
swallow the catch, which may amount to 1 200 1. in volume and weigh
over a ton. Ingebrigtsen (1929) described two methods of catching krill
employed by the humpback whale :
" One was to lie on its side on the surface and swim round in a circle
a t great speed, while it lashed the sea into a foam with flukes and tail
and so formed a ring of foam. The frightened ' krill ' gathered together
in the circle. This done the humpback dived under the foam ring and
a moment later came up in the centre to fill its open mouth with
' krill ' and water, after which it lay on its side, closed its mouth, and
the catch was completed.
" The other method was to go a short distance below the surface
of the water, swimming in a ring while at the same time it blew off.
The air rose to the surface like a thick wall of air bubbles and these
THE BIOLOGY O F EUPHAUSIIDS
animals. Marr (1962), in his magnificent monograph on the main
Antarctic species, Euphausia superba Dana, describes the extent of the
predation of the baleen whales on this organism. Hickling (1927) stressed
the importance of Meganyctiphanes norvegica to the hake fishery in the
southern Irish Sea and Poulsen (1926) showed that this crustacean was
essential to the fisheries of Skagerrak, especially for herring and mackerel.
Both M . norvegica and Thysanoessa raschii are important, in certain
coastal areas, to herring and mackerel. I n their account of whaling and
fishing in the North Atlantic, Hjort and Ruud (1929) repeatedly mention the importance of euphausiids, especially Meganyctiphanes
norvegica and Thysanoessa inermis as whale food and in the economy of
northern seas. The pilchard and mackerel shoals in the English Channel
(Lebour, 1924) feed to a large extent on Nyctiphanes couchii (Bell).
Other euphausiids are important in the Pacific Ocean mainly as food
of whales. Euphausia paciJica Hansen around Japan, Thysanoessa
inermis and T . longipes Brandt in the northern Pacific and T . macrura
G. 0. Sars and Euphausia crystallorophias Holt and Tattersall, along
with E . superba, constitute the food of the Antarctic whales.
It is not their numbers alone that render euphausiids so important
in the food chains of higher marine animals. What is so valuable to
their predators is their habit of living in great concentrations or swarms,
that migrate vertically as well as horizontally in response to light,
food, temperature, salinity, and many other factors of their environment. This swarming habit is particularly suitable for the feeding
mechanism of the baleen whales whose feeding has already been
described in the account by Scoresby. The great blue whale, the
largest animal ever to have existed, lives exclusively on euphausiids and
Collett (1911-12) has told how it swims back and forth in a swarm of
them with its mouth wide open, often turning on its side or back to
swallow the catch, which may amount to 1 200 1. in volume and weigh
over a ton. Ingebrigtsen (1929) described two methods of catching krill
employed by the humpback whale :
" One was to lie on its side on the surface and swim round in a circle
a t great speed, while it lashed the sea into a foam with flukes and tail
and so formed a ring of foam. The frightened ' krill ' gathered together
in the circle. This done the humpback dived under the foam ring and
a moment later came up in the centre to fill its open mouth with
' krill ' and water, after which it lay on its side, closed its mouth, and
the catch was completed.
" The other method was to go a short distance below the surface
of the water, swimming in a ring while at the same time it blew off.
The air rose to the surface like a thick wall of air bubbles and these