Evert though this method was applied for many years by local
Î;
Fisher—men, its detailed description in given here for the rst time.
The idea of using oats came from fishermen and personal
observations that C. hzppurus prefers shade casts of boats, ships and
.
floats. In this study, the two types of floats were employed.
The collected specimen were opened and the stomach contents
were
preserved in 10% formal in immediately to holt any further
digestion of food items. The food items were identied to the lowest
toxonomic levels. The following references were used as keys for
_
identication
of food
items EIEDL
(1970),. LŸTHGOE and
LYTHOE (1971), and FÏSHER (1973).
index of relative importance (HU) for each prey item for each
year was calculated using the Pinkas, Oliphant, and Everson's (1971)
formula :
lR1=(% N+ %V) . % EQ
_
Where, %N = Percent number of prey item.
%V = lts..percent volume
‘
and %FO. = its frequency of occurence.
The appliquation of 1.R.l. was prefered in this study to give
more
information about the importance of food items in the stomache_
,
content
analyses. HYSLOP (1980) indicated that according to
MNDELË (1971) indices combining values are more representative
for the assessement of dietary importance in shes.
The percent similarity index (PSI) for the presence of food
items in the stomachs of C. hz‘ppurus between to two years (1981 and
1982) was eastimated following ODUM (1991) :
.
2
PSI :
——Ç—
(100)
-
A + B
.
where, A,= the number of food items in 1981.
B = the number of food items in 1982.
C= the number of food items cummon in both years.
—60—
'