12. PREDATORS AND PARASITES
365
(1912b), however, states that during the Clare Island Survey off the
west coast of Ireland M . norvegica was the principal component of the
diet of salmon, trout, herring and mackerel in the spring.
Euphausiids have been recorded in the diets of fish from the North
Pacific. The Pacific herring feed heavily on Thysanoessa inermis and
Euphausia pacijim (Ponomareva, 1963). Likewise, the Pacific mackerel
in the northwest and the Sea of Japan and the Atka mackerel feed
predominantly on euphausiids, on many occasions on E. pacijca
(Nemoto, 1959; Ponomareva, 1963 ; Komaki, 1967a). Pacific cod,
Gadus macrocephulus Tilesius, off the Alaskan coast feed on Thysanoessa
raschii; no other species of euphausiids were eaten (Banner, 1954).
According to observations quoted by Ponomareva (1 963) euphausiids
are only consumed by codling in the northwestern Pacific and do not
feature to any great extent in the diet of adult cod. Euphausiids are of
great importance in the diet of the Alaska pollack (Banner, 1954;
Nemoto, 1959 ; Ponomareva, 1963), the species consumed in the North
Pacific being T . raschii, T . inermis, Euphausia pacijica, and Tessarabrachion oculatum. The humpback, chum, chinook and coho salmon also
feed on euphausiids (Ponomareva, 1963). Euphuusia pacijca is a
dominant food item of the sardine and mackerel in the Yellow Sea and
the southern region of the Sea of Japan and Komaki (1967a) records
the sand eel, Ammodytes personatus Girard, as an important predator
in Japanese coastal areas ; farther south, Pseudeuphausia Zatifrons
replaces Euphausia pacijica in the diets of planktivorous fish.
Nath (1966) studied the food of fish off the Travancore coast and
found that Pseudeuphausia latifrons was important in the diets of
Russell’s scad, Decapterus russelli (Ruppell), and the frigate mackerel,
Auxis thazard (Lacephde), but was not important in the diet of the
Japanese thread f k bream, Nemipterus japonicus (Bloch).
The stomach contents of South African fish were examined by
Davies (1949). He reports the presence of Euphausia similis, a species
of Thysanopoda which he names T . distinguenda, and Nyctiphanes
ccvpensis which he calls N . australis. Later authors, Boden (1954) and
Nepgen (1967), do not comment on these identifications and since
Thysanopoda distinguenda is not a valid species there is some doubt
as to the true identity of this species. The Cape stockfish, Merluccius
capensis (Castelnau), feeds predominantly on Euphuusia similis and
Thysanopoda distinguenda (? ) throughout the year, these organisms
constituting more than half of its general diet. These euphausiids
are also eaten by Myctophum humboldti (Risso), Maurolicus pennanti
(Walbaum), and Coelorhynchus fasciatus (Gunther), especially by
the young of the last species. The Cape John Dory, Zeus capensis
365
(1912b), however, states that during the Clare Island Survey off the
west coast of Ireland M . norvegica was the principal component of the
diet of salmon, trout, herring and mackerel in the spring.
Euphausiids have been recorded in the diets of fish from the North
Pacific. The Pacific herring feed heavily on Thysanoessa inermis and
Euphausia pacijim (Ponomareva, 1963). Likewise, the Pacific mackerel
in the northwest and the Sea of Japan and the Atka mackerel feed
predominantly on euphausiids, on many occasions on E. pacijca
(Nemoto, 1959; Ponomareva, 1963 ; Komaki, 1967a). Pacific cod,
Gadus macrocephulus Tilesius, off the Alaskan coast feed on Thysanoessa
raschii; no other species of euphausiids were eaten (Banner, 1954).
According to observations quoted by Ponomareva (1 963) euphausiids
are only consumed by codling in the northwestern Pacific and do not
feature to any great extent in the diet of adult cod. Euphausiids are of
great importance in the diet of the Alaska pollack (Banner, 1954;
Nemoto, 1959 ; Ponomareva, 1963), the species consumed in the North
Pacific being T . raschii, T . inermis, Euphausia pacijica, and Tessarabrachion oculatum. The humpback, chum, chinook and coho salmon also
feed on euphausiids (Ponomareva, 1963). Euphuusia pacijca is a
dominant food item of the sardine and mackerel in the Yellow Sea and
the southern region of the Sea of Japan and Komaki (1967a) records
the sand eel, Ammodytes personatus Girard, as an important predator
in Japanese coastal areas ; farther south, Pseudeuphausia Zatifrons
replaces Euphausia pacijica in the diets of planktivorous fish.
Nath (1966) studied the food of fish off the Travancore coast and
found that Pseudeuphausia latifrons was important in the diets of
Russell’s scad, Decapterus russelli (Ruppell), and the frigate mackerel,
Auxis thazard (Lacephde), but was not important in the diet of the
Japanese thread f k bream, Nemipterus japonicus (Bloch).
The stomach contents of South African fish were examined by
Davies (1949). He reports the presence of Euphausia similis, a species
of Thysanopoda which he names T . distinguenda, and Nyctiphanes
ccvpensis which he calls N . australis. Later authors, Boden (1954) and
Nepgen (1967), do not comment on these identifications and since
Thysanopoda distinguenda is not a valid species there is some doubt
as to the true identity of this species. The Cape stockfish, Merluccius
capensis (Castelnau), feeds predominantly on Euphuusia similis and
Thysanopoda distinguenda (? ) throughout the year, these organisms
constituting more than half of its general diet. These euphausiids
are also eaten by Myctophum humboldti (Risso), Maurolicus pennanti
(Walbaum), and Coelorhynchus fasciatus (Gunther), especially by
the young of the last species. The Cape John Dory, Zeus capensis