-14but when goatfish and mullet are excluded the average ts
53 per cent.
Comparison of the Decline of Radioactivity by Species
A comparison of the decline of radioactivity in two specles with different feeding habits is made in Figures 3 and 4.
Surgeonfish, with herbivorous habits and grouper, with carnivorous habits, were selected as representing the conditions that
probably prevailed in the fish in the vicinity of Belle Island.
Por comparisons of other species, reference may be made to Pigures 7 through 10, which depict the decline in goatfish and
mullet tissues.
As has been pointed out, goatfish and mullet,
because of their movement along the reef from island to island,
are not strictly comparable to Belle Island "resident" fish,
and the decline trends apparently reflect these differences.
Surgeonfish and groupers were obtained fairly regularly
throughout the period of investigation.
The former feed prin-
cipally on filamentous algae (Dawson, et al., 1955), whereas
the groupers feed principally on fishes.
The radioactivity in
the surgeonfish, Figure 3, declines at a greater rate than that
of the groupers, Figure 4, for all tissues for the first 50 to
100 days safter the shot.
For example, muscle tissue of surgeon-
fish contained approximately four times as much radioactivity
as that of the grouper immediately after the shot, but by 125
days the two species contained similar amounts.
Comparison of the Decline of Radioactivity in Fish with that of
with
In Pigure 5 the radioactivity in surgeonfish viscera is