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International Journal of Marine Science 2014, Vol.4, No.46, 1-12
http://ijms.biopublisher.ca
2
elasmobranchs’ exploitation seems to be highly
unsustainable as there are serious concerns owing to
drastically declining populations (Séret et al., 2010).
In response to global concerns over dwindling stocks
of elasmobranchs as a result of overexploitation,
studies pertaining to the biological traits of
elasmobranchs (Cortés, 2000; Ebert et al., 2008;
Abdurahiman et al., 2010), their population dynamics
(Walker and Heessen, 1996; Walker and Hislop, 1998),
status of exploitation (Compagno, 1990; Bonfil, 1994)
and its effects on their stocks (Stevens et al., 2000;
Stobutzki et al., 2002) have received attention of
fisheries researchers recently (Stevens et al., 2000).
Rapid changes in demersal fishing effort as well as
catch trends in the recent years along with alterations
in water quality in the coastal waters and increased
removal of elasmobranchs and their prey species have
exacerbated the deleterious effects on the
elasmobranchs populations. Hence, it was pertinent to
evaluate the status of elasmobranch populations
through continuous monitoring. Moreover, the
elasmobranchs catch and their prey items would
enable to assess the changes in their populations and
its dependence on prey items. Against this background,
an attempt have been made to provide baseline
information on species composition, spatio-temporal
variations in occurrence, size class and diet of
dominant elasmobranch species collected from the
fishing grounds of Goa in this communication. Further,
an attempt has also been made to provide a better
insight into the status of exploitation and utilization of
these resources based on elasmobranch landings of
Goa during 1969–2004.
1 Results
1.1 Environmental variables
Sea Surface Temperature (SST) range during the
entire study period was 26.02 – 31.03
℃
with a
mean value of 28.86 ±1.14
℃
.
1.2 Biological aspects
1.2.1 Species composition
A total of 10 elasmobranch species (Table 1) were
observed in the inshore trawl catches. Among these,
only three namely
C. griseum, H. walga
and
S.
laticaudus
were found to occur in 16, 15 and 10 % of
the trawl hauls, respectively (Table 1) indicating a
sizeable contribution of these species to the total
elasmobranch catch. However, the contribution of the
other seven species was negligible (<0.05 %; Table 1)
highlighting the rarity of their occurrence. Further,
only seven species namely
S. laticaudus, C. griseum,
H. walga, Himatura gerrardi
(Gmelin, 1789),
Aetobatus flagellum
(Bloch and Schneider, 1801),
Glaucostegus granulatus
(Cuvier, 1829) and
Rhinobatus
obtusus
Müller and Henle, 1841 were found to occur
off both North and South Goa; two others namely
Neotrygon kuhlii
(Müller and Henle, 1841),
Pastinachus
sephen
(Forskål, 1775)
were found off North and
Himantura uarnak
(Gmelin, 1789) was found only off
South Goa.
Table 1 Species composition, occurrence and size range of elasmobranch species examined during the present study
Sr.
No.
Species
N
Frequency of
occurrence (%)
Size range
(cm)
Lm (cm)* Juveniles
(n)
Adults (n)
1
Chiloscyllium griseum (Müller & Henle, 1838)
62
16.00
11 – 581
30.6–55.01 31
31
2
Scoliodon laticaudus (Müller & Henle, 1838)
10
15.00
15–571
32.6–58.41 84
24
3
Himantura walga (Müller & Henle, 1841)
63
10.00
5–372
19.8–35.42 45
18
4
Aetobatus flagellum (Bloch & Schneider, 1801) 10
0.05
20–1052
29.9–53.72 06
04
5
Himantura gerrardi (Gmelin, 1789)
07
0.03
9–282
73.8–132.4 07
00
6
Glaucostegus granulatus (Cuvier, 1829)
06
0.03
9–251
99.3–128.2 06
00
7
Rhinobatus obtusus Müller & Henle, 1841
05
0.04
20–301
37.5–67.31 03
02
8
Himantura uarnak (Gmelin, 1789)
03
0.02
22–352
73.8–132.4 03
00
9
Pastinachus sephen (Forskål, 1775)
01
0.01
352
68.2–1242 01
00
10 Neotrygon kuhlii (Müller & Henle, 1841)
01
0.01
142
29.2–52.42 01
00
Note: 1 total length 2 disc width