International Journal of Marine Science 2015, Vol.5, No.48: 1-7
3
Survey of India (SoI) topographic map nos. 82 O/11,
82O/12, 82 O/15, 82 O/16, 82P/9, 82P/10, 82P/11,
82P/12, 82P/13, 82P/14, 82P/15, 82P/16, 83M/5 and
83M/9 on 1:50,000 scale. The satellite Images LISS
III were collected from the NRSC Hyderabad, India,
Bhuvan and also from USGC. The present study is
confined to both the plain and hill areas because
drainage anomalies in the plains and hills indicate the
influence of subsurface structures, which are active in
nature (Saha et al.,
2006; Saders and Tabuchi, 2000;
Das et al., 2014 b
).
4 Results and Discussion
River Siang, a hill-Stream of 1
st
order river; had
colluvial (landslide from adjacent hill slopes delivering
sediments and organic matter) valley segment and
pool-riffle type of reach. This reach type was most
commonly associated with small to mid-size streams
and was a quite prevalent type of reach in the rheophilic
zones. On the other hand, runs were generally laminar
flow of water with sandy substratum. Pools, riffles and
runs were generally found to dominate the micro-habitat
type with frequent occurrence of trench pools. River
Siang was said to be more entrenched based on
V-shaped valley segment. The substrate type had been
found to be dominated by boulders, gravels and cobbles
with frequently-occurring quite large number of boulders
and some bed rocks. This kind of habitat with concomitant
physico-chemical characteristics of water was said to
be a suitable feeding and breeding ground for
Tor
spp.
and
Neolissochilus
spp.
The substrate of River Siang was dominated by
boulders. The level of embeddedness was high for
large boulders and low for small cobbles. About 57%
of the sample site was covered by boulders, 18% by
thick layer of cobble, sand and gravel 24% each and
remaining by silt and clay particles 1% showed in
Figure 2. The boulders and cobbles provided hiding
and spawning place for many hill stream fish species.
The riparian type was generally mesoriparian while
the riparian vegetation type is generally deciduous
trees with some amount of shrubs and grasses.
Different types of fish covers had been recorded in
River Siang ranging from undercut bedrock to
bottom-free big boulders and pools. Riparian land use
pattern mainly involves human habitation and some
amount of agriculture through ‘Jhum’ cultivation.
Field observations revealed differences in habitat prefer-
Figure 2 The Substrate Composition of River Siang
ences among the fishes of different size groups.
Nevertheless, the fishes in River Siang seem to prefer
deep pools as one of their favourable habitats in view
of depth, providing strong cover to them. However,
they also make use of covers like bottom-free big
boulders, undercut banks,
etc
. (Table 1). Riparian
vegetation did not seem to provide much cover to
these fishes.
Habitat Inventory of River Siang, in the province of
Arunachal Pradesh, was studied in six sectors, two
sectors each in the upstream, mid-stream and
downstream stretches. The study revealed differences
in valley segment among the different sectors of the
River Siang. In the plain region of the river, the valley
segment was alluvial; while, in the true hill stream
stretches
i.e.
in the upstream regions of the river, the
valley segment was colluvial. The latter makes the
habitat colonisable for the rheophilic fishes, most of
which had developed adhesive apparatus on the
ventral surface of the body in order to withstand the
fast torrent of the river. Further, colluvial valley
segment provides a diversity of micro-habitats while
the alluvial valley segment generally showed only
regime type of reach. Moreover, the River Siang was
generally wider where there was alluvial valley
segment. The fish covers in the studied river had been
found to be mostly turbulence and depth. In some
regions, fish cover was dominated by overhanging
vegetation. The substrate type in the hilly portion of
the River Siang was found to be dominated by gravels,
cobbles, boulders and bedrocks; while, in the plain
portion of the river, the substrate type mostly consists
of fines. It was mesoriparian in the River Siang. But
the riparian vegetations vary from shrubs to trees in
the different regions of the river. Signs of erosion had
been predominantly visible in all the studied segments
of the River Siang.
