FISH SPECIES AROUND RIVERBANK PROTECTION STRUCTURE AT SIRAJGANJ
Presented By:
Mahmud Hasan Tuhin
Research Assistant
IWFM
BUET
Presentation outline
Background
Study area
Structure around Sirajganj town
Methodology
Results
Conclusion and Recommendation
2
Background
Construction of bank protection structures have modified the flow
regime.
Changes in river flow regimes are well recognized as a cause of
changes to river geomorphology and habitat.
Change in flow regime and also change the river habitat and biota.
The change in flow regime might introduce alien species, have had a
dramatic, negative impact on native fishes.
3
Background
4
Different erosion protection
structures such as Groyen, Spur,
Revetment, Hardpoint are common.
River Jamuna has all of these
structures makes it as a highly
trained river
The right bank have the
maximum numbers of the
structures.
Figure: Schematic Diagram of structures
of Jamuna River
Study Area
5
Jam
un
a R
iver
Sirajganj Hardpoint
Bangabandhu Bridge
Guide Bund
Sirajganj Town
Sirajganj Hardpoint is situated at the east
side of the Sirajganj town and the right bank
of the Jamuna river.
Bangabandhu Bridge is located 7 kilometer
south (Downstream) of the hard point.
Figure: Sirajganj town and Jamuna river
6
Study Area
Sirajganj Hardpoint from different view point
Upstream termination of Hardpoint from upstream side
Upstream termination of Hardpoint from downstream side
Revetment work of Hardpoint Revetment work of Hardpoint
Methodology
7
Social analysis(Primary data)
Ecological analysis (Primary data)
Technical analysis(Primary data and Secondary data)
Socio-eco-technical approach
Focus Group Discussion (FGD) with
fishers
Key informants interview (KII)
On spot species identification
On spot species change information
collection
Aquatic Doppler current profiler (ADCP)
data
Bathymetric data
On site float track data
Results
9
Flow pattern near the Sirajganj hard point
Figure : Primary vortex and secondary vortex in scour hole around Sirajganj hard point
The flow pattern continuously changes due to changing morphology of sand bars,
roughness and the configuration of the bank protection structure.
The velocity adjacent to the hard point is doubled of the approach flow velocity. It
is also evident that the deep scour hole is located near the upstream of hard point.
Clock wise and anti clock wise vortices creates deep scour hole near the
structure.
(Source: Modified from Nazim et. al, 2010)
Results
10
Analysis of float data of Sirajganj hard point
Figure: Flow velocity near Sirajgonj hard point
GPS float track data
It is seen that the water velocity
suddenly increased (>2.5 m/s) at
the upstream of the hard point
marked by the dotted arrow .
High velocity was observed up
to one kilometer downstream from
the upper termination
After one kilometer down stream
of the upper termination, the
velocity decreased (between 1 to
2.5 m/s) and marked by the solid
arrow.
(Source: Field Study, 2010)
Results
11
Analyses of bathymetric data of Sirajganj hard point
Figure: Rapid formation of scour holes near hard point
Deep scour hole formed near the upper termination of the hard point. Along
the revetment work, several deep scour holes were found in several places.
10 day interval bathymetric data shows that, deep scour hole formed. These
scour holes also moved with time and with the change of the river flow.
(Source: BWDB Field Survey, 2010)
Date: 6 June, 2010) Date: 17 June, 2010)
No Scour Hole Deep Scour Hole formed
Results
12
Change in fish habitat
Causes of fish species change
Change in flow pattern, river bathymetry, water velocity, formation of
deep scour hole etc. affect the natural habitat of the river.
Species like small and carp prefer low velocity for their grazing,
migration and wandering.
Some species like Catfish, prefer high velocity and deep scour holes
for their resting, grazing and drifting.
After construction of the hard point, the velocity of the river near the
adjacent of structure have increased.
Deep scour holes formation, shifting of river bed and other
morphological changes directly affect the fish habitat.
(Source: Field Study, 2010)
Results
13
Change in fish species for habitat change
(Source: Field
Study , 2010)
Name of dominant species
Position after construction before construction
*1Air (Sperata aor) Rui (Labeo rohita)
2Baghair (Bagarius bagarius) Catol (Catla catla)
3 Kalbaus (Labeo calbaus) Ilish (Tenualosa ilisha)
4Pangas (Pangasius pangasius) Air (Sperata aor)
5Boal ( Wallagu attu) Baghair (Bagarius bagarius)
6Mrigal (Cirrhinus mrigala) Boal ( Wallagu attu)
7 Rita (Rita rita) Puti (Puntius sophore)
8Khorsula (Rhinomugil corsula) Kajuli (Ailia coila)
9 Ilish (Tenualosa ilisha) Mrigal (Cirrhinus mrigala)
10Ghaura (Clupisoma garua)
Chingri (Shrimp) (Macrobrachium
rosenbergii)
11 Gang Tengra (Gagata cenia) Bailla (Awaous guamensis)
Table : Major fish species found near the Sirajganj hard point
Change in Fish composition before and after construction of the hardpoint
AvailabilityHigh
AvailabilityLow
Results
14
Change in fish species for habitat changeChange in Fish composition
Figure : Change in fish composition near hard point (Source: Field Study, 2010)
Available fishes are divided into four major groups
Catfish group containing Air (Sperata aor), Baghair (Bagarius bagarius), Pangas
(Pangasius pangasius), Boal (Wallagu attu), Rita (Rita rita), Ghaura (Clupisoma garua),
Gang Tengra (Gagata cenia);
Carp fish group containing Rui (Labeo rohita), Catol (Catla catla) Mrigal (Cirrhinus
mrigala);
Small fish group containing Puti (Puntius sophore), Kajuli (Ailia coila), Chingri (Shrimp)
(Macrobrachium rosenbergii), Bailla (Awaous guamensis), Khorsula (Rhinomugil corsula);
Ilish (Tenualosa ilisha) as an independent group
Results
15
Some Catfish species caught around the hardpoint
Air
Boal
Kalbaus
Rita
Baghair
(Source: Field Study, 2010)
Results
16
Local fishers knowledge about habitat change near Sirajganj hard point
Low water velocity of the river was observed before the bank protection
structure, because the river was wider and deeper with fewer sandbars.
After the construction of hard point, formation of high sand bars (Char land) has
increased. “Ulta oure” (back flow), “Ghona” (deep hole / scour hole), “Dhar” (High
velocity) etc. have also increased than earlier time.
Large cat fish species prefer deep places of river bed for resting, so they take
rest inside the Ghona.
Small fish cannot swim against the high velocity near the hard point and they
trapped inside the strong return flow. At that time large catfish species hunt them.
Some time a good number of large fishes is caught by the fisher near the hard
point, but it doesn’t indicate that the place is fish friendly habitat but rather a
natural trap for fishes.
(Source: Field Study, 2010)
Conclusion and Recommendation
17
Riverine structure induced morphological and hydraulic changes
modify the natural fish habitat of the river.
For such alteration of the habitat, available species are also
changed.
After construction of Sirajganj hard point, cat fish species like Air,
Baghair and Kalbaus have replaced the previously common carp
species like Rui and Catol.
The availability of predator fish species has also increased near
the hard point area.
The design and planning of future interventions would need to be
modified in order to maintain natural fish habitat.
Fish friendly and eco friendly bank protection structures should
introduced for the river training works.
Top Related