- 15 fishes with a correspondingly great variation in feeding
habit make this a very difficult area in which to summarize results.
In general,
habit
the fishes may be divided by feeding
into three groups:
carnivores.
algae,
the herbivores,
omnivores and
Since the herbivores feed directly on the
the radioisotopes concentrated from the water by
the algae are passed on directly to the fish,
the fish to the animal eating the fish.
and from
The herbivores,
represented by such fishes as the surgeonfish and
parrotfish, have the greatest amount of radioactivity
of the three major groups.
Omnivorous fish such as the damselfish have less
contamination than have the herbivorous fish,
for they
feed on more complex organisms.
The herbivorous and omnivorous fish tend to
concentrate the same isotopes found in the plankton
except for the radioisotopes which are taken up only
in trace amounts by these animals.
zn°> usually accounts
for 50 percent or more of the total radioactivity in the
organs of these fish and Fe? >? comprises a major part
of the remaining activity.
The radioactive isotopes of
cobalt account for 7 to 20 percent of the radioactivity
and Mn°* 2 to 6 percent.
The minimum concentrations of radioactive material
are found in the carnivores,
for these fishes,
like the
reef-dwelling groupers,
or the roaming carnivores,
the tuna and barracuda,
obtain their
like
“tag" of radio-
active material only after it has been passed through a
number of living forms which select,
various radioisotopes.
retain,
or reject
With the passage of time