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International Journal of Marine Science 2014, Vol.4, No.46, 1-12
http://ijms.biopublisher.ca
3
Quantitative analysis of trawl catch data collected
during the present study revealed a meagre
contribution from elasmobranchs (0.42 and 0.97 % by
abundance and weight, respectively). Subsequently,
the above data was assorted to represent
‘pre-monsoon’ and ‘post-monsoon’ seasons. The
temporal trends revealed no marked differences
between the seasons
(Figure 1a, b). Further, analysis
of elasmobranch abundance and weight data between
the two sites (North Goa and South Goa) revealed
significant variations in both abundance (α = 0.001,
P
= 0.000191) and weight (α = 0.001,
P
= 2.14E-08).
Similarly, annual landings of Goa (2006–2010;
Directorate of Fisheries, Government of Goa; Figure 2)
indicated greater contribution from South Goa (α =
0.01,
P
= 0.00295).
Figure 1 Seasonal variations in elasmobranch abundance (a) and weight (b)
Figure 2 Elasmobranch landings along North Goa and South
Goa) during 2006-2010
1.2.2 Size class and life stages
The observations on the size and their comparison
with L
m
values (Froese and Pauly, 2011) indicated that
72% specimens were juveniles, whereas only 28%
were adults (Table 1). Species wise data indicated that
S. laticaudus, H. walga, A. flagellum
and
R. obtusus
were dominated by juveniles,
C. griseum
was represented
equally by juveniles and adults, and the other five
species were represented exclusively by juveniles (Table 1).
1.2.3 Diet analysis
Among the 165 guts examined, 27.27, 26.06 and
46.67% were empty, partially filled and gorged,
respectively. The percentage of empty stomachs in
S.
laticaudus
,
C. griseum
and
H. walga
was found to be
17, 31 and 31, respectively. Analysis of their stomach
contents revealed 13 prey items (Table 2). The order
of prey importance for all the observed specimens was
teleosts (45.95%
I
RI
) followed by crustaceans (40.19%
I
RI
) and molluscs (13.83%
I
RI
). The Indian Oil sardine,
Sardinella longiceps
was the most important prey item
of the elasmobranchs (Table 2). Further, analysis of
the stomach contents revealed that crustaceans
(58.85%
I
RI
), teleosts (81.50%
I
RI
) and cephalopod
molluscs (55.79%
I
RI
) dominated the diets of
S.
laticaudus, C. griseum
and
H. walga,
respectively (Table 2).
Gut content analysis of different size groups of
S.
laticaudus
(Table 3) revealed that crustaceans
(96.65 %
I
RI
) were the major prey item of small
individuals (15–25 cm). Medium sized individuals fed
on a mixed diet of crustaceans (60.05%
I
RI
), teleosts
(33.14%
I
RI
) and molluscs (6.79 %
I
RI
). The diet of
large individuals was dominated by teleosts (94.72%
I
RI
), whereas crustaceans were absent.