-llnaturally occurring radionuclide, these are the fallout radionuclides which are most likely to be present in biological samples.
With fish samples there was a question about the presence
of cobalt-57 and cerium-144,
or both,
since the gamma photopeaks
for these two radionuclides are similar.
Previous radiochemical
analyses have shown that cobalt-57 is found in the internal
organs of marine fish and invertebrates and that radiocerium
is not
(Lowman et al.,
1957 and 1960),
thus it was assumed that
only cobalt-57 was present.
The levels of strontium-90 in a few samples of water and
fish were determined by a radiochemical method which combines
standard wet chemical techniques and the technique of ion-excharge
chemistry
(Kawabata and Held,
1958).
Since the time elapsed between collection and counting may
be as great as six months, errors in estimating activity in shortlived radionuclides,
such as iodine-131,
are large.
RESULTS
Fish
In Table 3 the data on the radionuclide content of three
tissues of yellowfin tuna,
summarized.
A total of
during Cruises
56,
57,
based on the date of collection,
107 yellowfin were
and 59.
This
caught,
most
species accounted
are
of them
for
63
per cent of the total number of specimens collected and analyzed.