3. Introduction
Geographical location
21⁰-23⁰ N latitude
88-89⁰E longitude
West Bengal
Largest estuarine ecosystem in India, with an area
8029 km2
• It forms world’s largest delta (sundarban), endowed
with largest mangrove vegetation (4,264 km2)
4. Cont…
Distributary of the river Ganga
Positive, mixohaline in nature
Average tidal elevation is 5.7m
5. Different zones
For estimating fish landings, CIFRI divided this
estuarine system into the following zones:
zone 1-Nabadwip to Konnagar (upper zone of the freshwater
zone)
Zone 2- Konnagar to Diamond harbour (middle zone of the
Hoogly estuary or the ‘gradient zone’)
Zone 3- Diamond Harbour to the mouth of the estuary
including entire lower Sunderbans (lower or marine zone of
the system)
Zone 4- includes river Rupnarain.
Zone 5- includes river Matlah around port canning.
6.
7. Physico-chemical parameters of the estuary
Soil texture
Temperature
7.8- 8.8
Salinity
0.5- 32.5
DO
•
16 0 C – 330 C
pH
•
mostly clay silty loam
4.8- 8.9
Temperature and salinity are the most significant factors that determining
the fishery.
The maximum and minimum temperatures recorded in the pre-monsoon
and post-monsoon respectively, in all zones except Zone 4 ,where the
maximum temperature prevails during monsoon
9. Fishery resources
172 species recorded,73- freshwater and 99 occupy the
saline zone
Fish fauna classified into:
- residents (mullets, threadfins, sciaenids, sea bass)
- migratory or transient (Hilsa, Pama pama, pangasius,
rosenbergii)
Dominated fish spp.
T. ilisha
51%
H. nehereus
11.3%
Pama pama
5.7%
Setipinna phasa
4.7%
Trichiurus spp.
4.2%
Penaeds prawn
4.35%
10. Cont…
Other important fish species :
Polynemus paradiseus, P.indicus, Eleutheronema
tetradectylum, Lates calcarifer, Pangasius pangasius, Liza
parsia, L.tade, Rhinomugil corsula, Pampus argenteus ,Coilia
dussumeiri, Mystus spp. , Johnius dussumeiri , Clupisoma
garua, Wallago attu, Sperata seenghala, Ompok bimaculatus
and Rita rita etc.
Prawns: Penaeus monodon, P. indicus, Metapenaeus
brevicornis, M. monoceros ,Parapenaeopsis sculptilis, P.
stylifera, Macrobrachium spp.
Crabs : S. serrata, P. pelagicus
11. Fish production
The average annual prawn and fish yield increased from
3,204 t (1960-63) to 117,639 t in 2010-11.
12. Cont….
• Maximum average catch (82%) is obtained during winter
months of Nov-Jan
• Minimum average catch (3.5%) is during the summer months
of Mar-June
• Zone-wise total annual catch (92 to 95%) comes from ZoneIll, while, Zone 1, II and IV together contribute 5 to 8%
only
13. Hilsa fishery
The average hilsa production have been increased from
1427 t (1957-74) to 10,083t (2003-04)
About 80-90% hilsa are captured during July- Oct.
The peak spawning period is noticed during Sep- Nov.,
although this species is prolific spawner
Winter migratory Bag net fishery: The fishermen migrate to the
lower zone of estuary and they remain engaged in fishing during the
end of Oct. to middle of Feb. The total landing of this fishery with an
avg. 28536.7 tones. This fishery contributed 60-65% of total yield of the
estuary. The net used is locally known as been jal (a migratory bag net).
14.
15.
16. Source of seed
• A potential source of cultivable fish and prawn seed which are
being used as stocking material for brackish water
aquaculture
P. monodon (Bagda), P.indicus, Metapenaeus. monoceros, M.
brevicornis, Liza spp. Lates calcarifer , M. rosenbergii, Hilsa
etc.
17. Threats
Deteriorating ecological characters due to anthropogenic
pressure
Overexploitation of faunal resources
Destruction of mangroves
Siltation and formation of sand bar
Flood and shortage of fresh water discharge
Hydraulic structure (dams, barrages, weirs)
wanton destruction of juvenile hilsa
18. Conclusion
• There is a urgent need to protect estuarine
envt. From pollution hazards (Agri., Industrial.
and Domestic effluents).
• Estuarine envt. should be judicially exploited
so that the fish, prawn and their recruits are
not destroyed
• Mangrove preservation
• Intensive seed collection should be stopped
