12. PREDATORS AND PARASITES
361
The importance of euphausiids as food of herring in Icelandic waters
was demonstrated by Jespersen (1932), Fridriksson (1933-1937),
Saemundsson (1937), Stephensen (1938), and Jakobsson (1958). Across
the Atlantic, Moore (1898) stated that Meganyctiphanes norvegica was
the most important food of herring off the east coast of America and
later Bigelow and Welsh (1925) found that the herring in the Gulf of
Maine fed on copepods and euphausiids but when both were present
they selected the euphausiids in preference to the copepods. Rudakova
(1959) studied the food of the Atlantic Scandinavian herring over a
period of several years and concluded that they feed primarily on
euphausiids during the months February to April, on the copepods
Calanus Jinmarchicus and C. hyperboreus Krayer and species of the
amphipod genus Themisto during the summer, and on euphausiids,
Calanus species and Themisto species in the autumn. The euphausiids
consumed are Meganyctiphanes norvegica, Thysanoessa inermis, T .
raschii and Nematoscelis megalops.
I n European seas the cod, Gadus morhua L., is even more important
economically then the herring and the extent of its predation on
euphausiids is often considerable. It is quite evident from the literature
that cod feed on euphausiids but these are only predominant in the diet
on certain occasions, in certain sea areas, and in certain size classes of
fish. Thus, Saemundsson (1937) found Meganyctiphanes norvegica in
large numbers in the stomachs of cod off southeast Iceland but Meschkat
(1936) found the species to be relatively unimportant as food for the
populations of cod near the Westermann Islands ; Schmidt (quoted by
Einarsson, 1945) found that Thysanoessa inermis was the main food of
cod taken off north and east Iceland. Brown and Cheng (1946) found
Meganyctiphanes norvegica only in the stomachs of Icelandic cod and
not in those of cod from Bear Island or the Murman coast where
Thysanoessa inermis was an important item of the diet. On the other
hand, Zelikman (1958b) did find Heganyctiphanes norvegica along with
much larger numbers of Thysanoessa inermis, T . raschii, and T .
longicaudata in the stomachs of Murman cod. I n the Skagerrak,
Meganyctiphanes norvegica was definitely the principal food of the cod
(Poulsen, 1926) and Popova (1962) estimated that 20% of the food of
the cod in the Newfoundland Banks was M . norvegica. Cod in the Gulf
of St. Lawrence feed to some extent on Thysanoessa raschii and
T . inermis (Jolicoeur and Brunel, 1966).
Another important European food fish is the haddock, Helanogrammus aegleJinus (L.), but this species does not seem to prey on
euphausiids to the same extent as cod. I n fact, Zenkevich (1931)
reported that Dektereva found zooplankton to be unimportant in the
361
The importance of euphausiids as food of herring in Icelandic waters
was demonstrated by Jespersen (1932), Fridriksson (1933-1937),
Saemundsson (1937), Stephensen (1938), and Jakobsson (1958). Across
the Atlantic, Moore (1898) stated that Meganyctiphanes norvegica was
the most important food of herring off the east coast of America and
later Bigelow and Welsh (1925) found that the herring in the Gulf of
Maine fed on copepods and euphausiids but when both were present
they selected the euphausiids in preference to the copepods. Rudakova
(1959) studied the food of the Atlantic Scandinavian herring over a
period of several years and concluded that they feed primarily on
euphausiids during the months February to April, on the copepods
Calanus Jinmarchicus and C. hyperboreus Krayer and species of the
amphipod genus Themisto during the summer, and on euphausiids,
Calanus species and Themisto species in the autumn. The euphausiids
consumed are Meganyctiphanes norvegica, Thysanoessa inermis, T .
raschii and Nematoscelis megalops.
I n European seas the cod, Gadus morhua L., is even more important
economically then the herring and the extent of its predation on
euphausiids is often considerable. It is quite evident from the literature
that cod feed on euphausiids but these are only predominant in the diet
on certain occasions, in certain sea areas, and in certain size classes of
fish. Thus, Saemundsson (1937) found Meganyctiphanes norvegica in
large numbers in the stomachs of cod off southeast Iceland but Meschkat
(1936) found the species to be relatively unimportant as food for the
populations of cod near the Westermann Islands ; Schmidt (quoted by
Einarsson, 1945) found that Thysanoessa inermis was the main food of
cod taken off north and east Iceland. Brown and Cheng (1946) found
Meganyctiphanes norvegica only in the stomachs of Icelandic cod and
not in those of cod from Bear Island or the Murman coast where
Thysanoessa inermis was an important item of the diet. On the other
hand, Zelikman (1958b) did find Heganyctiphanes norvegica along with
much larger numbers of Thysanoessa inermis, T . raschii, and T .
longicaudata in the stomachs of Murman cod. I n the Skagerrak,
Meganyctiphanes norvegica was definitely the principal food of the cod
(Poulsen, 1926) and Popova (1962) estimated that 20% of the food of
the cod in the Newfoundland Banks was M . norvegica. Cod in the Gulf
of St. Lawrence feed to some extent on Thysanoessa raschii and
T . inermis (Jolicoeur and Brunel, 1966).
Another important European food fish is the haddock, Helanogrammus aegleJinus (L.), but this species does not seem to prey on
euphausiids to the same extent as cod. I n fact, Zenkevich (1931)
reported that Dektereva found zooplankton to be unimportant in the