65
The fact that the decline in the radioactivity was less
in the liver than in the muscle tissue would indicate that
the longer-lived transition element radioisotopes tended to
accumulate in the liver, while the shorter-lived fission
products accumulated in the muscle.
This does not seem
unreasonable as liver is known to be rich in iron and zinc,
and muscle is rich in potassium.
In mineral assemblages potas-
sium is often associated with the lanthanide elements which
constitute a sizeable proportion of the fission-product isotopes.
The greater decline of radioactivity in omnivorous than in
carnivorous fish (after 100 days after shot) suggests that the
longer-lived radioactive transition elements are somehow more
readily available to the carnivores than to the omnivores.
The high coefficient of variation of radioactivity measure-
ments in goatfish and mullet with respect to 10 other families of
reef fish,
considered in the light of the wider range of movement
of the former than is common for the other families,
that fallout radioisotopes
suggests
in the water of the lagoon had not
become effectively mixed by the time the fish were collected,
further,
and
that among different taxonomic groups of fish there are
probably differences with respect to selectivity for radioactive
materials.