192
THE BIOLOQY OX EUPHAUSIIDS
variations which are related to the seasonal variations in the occurrence
of planktonic crustaceans. Similar seasonal fluctuations in the occurrence of dinoflagellates in the stomachs of the euphausiids are related
to the changing density of these organisms in the plankton (Fig. 69).
Fisher and Goldie examined the seasonal occurrence of species of
Ceratium, Dinophysis, Peridinium, Prorocentrum, and Phalacroma and
M. norvegico
T mschii
60
20
100
a,
v 0
c 0 )
-
0 60
2c
i ' L
B
-
801
, .
i n
u
S'O'N'D'J 'F'tdA;A;M'J 'J 'A'S'O'N'D'J'F'M'A'M'J '
n
n
1 .n
1956
1957
1958
1962
1963
1964
FIG. 69. Seasonal variation in the percentages of Meganyctiphanes nowegica and
Thysanogssa raschii with (A) food present in their stomachs (shaded portion equals
percentage with stomach more than half full), (B) crustacean remains present
(shaded portion equals percentage with stomach containing fragments of compound
eyes) and (C) dinoflagellates present. (After Fisher and Goldie, 1959; Mauchline,
1966a).