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International Journal of Marine Science 2014, Vol.4, No.46, 1-12
http://ijms.biopublisher.ca
1
A Letter Open Access
Biological Aspects and Catch Trends of Elasmobranchs in the Inshore Waters of
Goa, West Coast of India
M. R. Hegde, V. P. Padate, C. U. Rivonker
Department of Marine Sciences, Goa University, Taleigao Plateau, Goa 403206, India
Corresponding author email
Tel. +91-9881345259
International Journal of Marine Science, 2014, Vol.4, No.46 doi: 10.5376/ijms.2014.04.0046
Received: 09 May, 2014
Accepted: 13 Jun., 2014
Published: 11 Aug., 2014
Copyright
©
2014 Hegde et al., This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article:
Hegde et al., 2014, Biological Aspects and Catch Trends of Elasmobranchs in the Inshore Waters of Goa, West Coast of India, International Journal of Marine
Science, Vol.4, No.46 1
-
12 (doi: 10.5376/ijms.2014.04.0046)
Abstract
Despite being the top predator, elasmobranchs are dwindling due to excessive fishing pressure. However, very few studies
along Indian coasts have focused on their eco-biological aspects. The present investigation during 2006–2010 and comprising 158
trawl samples (220 h effort) along the nearshore fishing grounds of Goa revealed that the elasmobranch population comprised 10
species (2 sharks, 6 rays and 2 skates). Analysis of spatial variation revealed significant variations between the regions (abundance, α
= 0.001,
P=
0.000191; weight, α = 0.001,
P
= 2.14E-08) suggesting high catches along southern region, owing to lesser fresh water
discharge due to absence of major estuarine system. Assessment of size class indicated that juveniles dominated the elasmobranch
population with few stray occurrences of adults. Dietary analysis of the three commonly observed species revealed the dominance of
teleosts (45.95%
I
RI
), followed by crustaceans (40.19%
I
RI
). Analysis of the catch trends (1969–2004) of elasmobranchs in this region
indicated meagre contribution (0.05–5.04%) to the total marine fish landings of Goa. Further, the catch trends displayed decrease in
recent times suggesting reduction in trophic level of the regional fishery perhaps caused by fishing out of carnivores coupled with
increased catches of low trophic level fishes as evidenced in the present study. These findings have implications for the trophic web
dynamics of the coastal waters, which in turn affect the coastal fisheries of the region.
Keywords
Shark fisheries; Spatial variation; Temporal variations; Diets; Goa; India
Background
Goa situated on the central west coast of India with
105 km long coastline and about 10,000 km
2
shelf
areas (Kurup et al., 1987) supports a wide array of
demersal and pelagic ichthyofaunal diversity
including elasmobranchs. Traditionally, the elasmobranch
fisheries of Goan coast consisted of catches taken with
beach seines (inshore), gill nets and hook-and-line
(offshore). Mechanization of fishing vessels (1963)
led to exploitation of bulk of the elasmobranchs as
by-catch of bottom trawlers operating in the nearshore
and offshore waters off Goa. Published literature (Raje
et al., 2007) suggests that 38 species including 26
species of sharks, nine species of rays and three
species of skates have contributed to the elasmobranch
fishery of Goa during 1969–2004 (CMFRI, 1979;
Kurup et al., 1987; Srinath et al., 2006) with an
average annual landing of 461.78 mt
per annum.
Amongst the commercially exploited elasmobranchs,
Scoliodon laticaudus
(Müller and Henle, 1838)
and
Sphyrna zygaena
(Linnaeus, 1758)
attract lucrative
markets for dried products (Hanfee, 1997), however
only large sized batoids are locally consumed.
Large-scale discarding of elasmobranch juveniles and
small sized individuals by trawlers might be the
reason for the inaccurate estimation of species
abundance and diversity.
Elasmobranchs being top predators play a major role
in regulating the population size and dynamics of
lower trophic level (LTL) fishes (Wetherbee and
Cortés, 2004; Séret et al., 2010). Targeted fishing for
elasmobranchs due to high demand for their meat, fins,
liver and other products has resulted in increased
global landings to the tune of 760,000 mt per annum
(Stevens et al., 2000). Further, intrinsic biological
traits such as slow growth rate, low fecundity (Holden,
1974; Jennings et al
.
, 1998; Ebert et al., 2008), high
fishing mortality coupled with juvenile discard push
some species to depletion, while endangering others
(Stevens et al., 2000). Although elasmobranchs have
been traditionally exploited, the present rate of