. 146 40 40 50 159 IOC 32 164 40 40 171 146 318 40 36 III 40 207 122 287 40 904 86 539 lOO 818 186 82 lOO lOO IOC 100 118 Fig. 14. Length frequencies of krill from the plankton and from whales' stomachs compared, both stomach samples and plankton samples having been collected on the same, or approximately the same dates. The number of older (O) and younger (Y) krill measured is given for each sample. The remarkable exclusiveness of the diet of the southern whales is paralleled among many far- eastern fishes, the Pacific cod for example, with over lOo abundant species to choose from, consistent
. 146 40 40 50 159 IOC 32 164 40 40 171 146 318 40 36 III 40 207 122 287 40 904 86 539 lOO 818 186 82 lOO lOO IOC 100 118 Fig. 14. Length frequencies of krill from the plankton and from whales' stomachs compared, both stomach samples and plankton samples having been collected on the same, or approximately the same dates. The number of older (O) and younger (Y) krill measured is given for each sample. The remarkable exclusiveness of the diet of the southern whales is paralleled among many far- eastern fishes, the Pacific cod for example, with over lOo abundant species to choose from, consistently selecting only four or five (Moiseev, 1957). As a result of the 2-year life-cycle of the krill the feeding-stuff available to the whales consists of two distinct broods, a younger, rising yearling or yearling class, and an older near-mature or 2-year old breeding stock that is reaching, or shortly about to reach, the end of its natural span. The whales feed indiscriminately on both. Sometimes the young brood is present in the stomachs, sometimes the old, or, as often happens, both broods may be present in the same stomach. In Fig. 14 I have plotted in 4-mm. groups the length frequencies of samples taken from whales' stomachs and compared them with samples taken directly from the plankton on the same, or approximately the same, dates (not
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