Government of IndiaDepartment of Ocean DevelopmentIntegrated Coastal and Marine

Area Management Project Directorate, Chennai

April 2002ICMAM-

PD

About Cochin Backwaters

Islands of Cochin

Ecological importance

Geomorphology

Landuse / Landcover

Biodiversity of Cochin Backwaters

Fishery Resources

Mangroves

Major threats to Cochin Backwaters

Management suggestion

Conclusion

Programme

Physico-Chemical Parameters

Water quality parameters - comparison

CONTENTS

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• This information system has been developed by the ICMAM Project Directorate of DOD under the project "Environment Management Capacity Building" funded by the International Development Association. Primary data on Physico-chemical and biological parameters were collected by School of Marine Sciences, Cochin School of Marine Sciences, Cochin

University of Science and Technology, CochinUniversity of Science and Technology, Cochin during

1998-99.

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The major objective of this study is to create an information system on the resources of Cochin Backwaters in order to help decision makers in effective monitoring and management of the biological wealth of this area.

Critical habitat information system for Cochin Backwaters is developed using relational-hybrid Geographical Information System (GIS).

A relational hybrid GIS uses the power of GIS to portray the geometry and topology of spatial objects while utilising the strong capabilities of the commercially available RDBMS (like Oracle, Informix, etc) to store voluminous attributes of the spatial data.

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The major components in the creation of the information system are

A. REMOTE SENSING :A. REMOTE SENSING : IRS IC LISS III data of June 1998 were used and analysed using ERDAS-IMAGINE 8.4 image processing software to study the landuse of this region.

B.FIELD SURVEYB.FIELD SURVEY: : Data on physico-chemical and biological parameters were collected in seven stations along the estuarine and neritic zones.

C. RELATIONAL DATABASE MANAGEMENT SYSTEMS C. RELATIONAL DATABASE MANAGEMENT SYSTEMS (RDBMS) :(RDBMS) : RDBMS is the acronym for “Relational Database Management Systems”. All the attribute data collected from the various sources were stored as separate tables in the Oracle database.

D. GEOGRAPHICAL INFORMATION SYSTEM (GIS) :D. GEOGRAPHICAL INFORMATION SYSTEM (GIS) : Geographical Information System (GIS) is a system for capturing, storing, checking, manipulating, analysing and displaying data which are spatially referenced to the earth.

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• The Cochin Backwaters is part of a long chain of lakes and canals extending between 9• 40' 12" and 10• 10' 46 N and 76• 09 52' and 76• 23' 57"E with its northern boundary at Azheekodu and southern boundary at Thannirmukham bund.

• Rivers, Periyar and Muvattupuzha discharge into the backwaters. The Thannirmukham bund regulates the flow from four rivers namely, Meenachil, Manimala, Achankovil and Pamba.

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• The islands off Cochin considered for study are Vypeen, Vallarpadam, Bolghatty . The total area of three islands is 56.95 sq.km (SOI toposheet, 1981) with a population of 1,88,251 (1991 census). The population density of these islands is 2158 sq.km. The main occupation of the islanders is fishing and agriculture.

VYPEEN ISLAND

VALLARPADDAM ISLAND

BOLGATTY ISLAND

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Vypeen island is the biggest

island and is bound by the Arabian Sea

on the Western side and the Cochin

Backwaters on the eastern side. The

total area of the island is about 1.49

sq.km.The inter-island accessibility is

only through boats. However, bus

services are available within the island.

VALLARPADAM ISLAND

BOLGATTY ISLAND

VYPEEN ISLAND IN COCHINBACKWATERS

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Vallarpadam lies between Vypeen

and

Bolghatty islands and covers an

area of

about 2.8 sq.km.

VALLARPADDAM ISLAND

BOLGATTY ISLAND

VALLARPADDAM ISLAND IN COCHINBACKWATERS

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The Bolghatty island is a long narrow

palm fringed island and is easily

accessible from the mainland by boats.

The Bolghatty palace is situated here

amidst 15 acres of lush green lawns built

by the Dutch. The total area of the

island is 2.61 sq.km.

VALLARPADAM ISLAND

VYPEEN ISLAND

BOLGATTY ISLAND IN COCHINBACKWATERS

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• The Salinity gradient in the Cochin Backwaters supports diverse species of flora and fauna

according to their tolerance for salinity.

• This tropical estuary with high productivity acts as a nursery ground for many marine and

estuarine finfish, molluscs and crustaceans.

• The low-lying swamps and tidal creeks with sparse patches of mangroves provide shelter to

juveniles of many important species.

• The areas of backwaters with fine sediments and rich organic matter support abundant and

diverse benthic fauna.

• The changes in the hydrology of the backwaters controlled by the seas play an important

role in regulating the migrant fauna of the estuary.

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The Cochin Backwaters is a coastal plain and

topographically a low lying area. It is

characterised by its long axes running parallel

to the coast and is separated from the sea

by barrier spits interrupted by tidal passes. It

has a free permanent connection with the sea.

It has three dredged channels namely the

approach channel oriented along east-west

direction and the two inner channels located on

either side of the Willingdon Island.

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The area around Cochin Backwaters comprises

a variety of landuse/landcover classes such as

Agriculture, aquaculture, plantations,

wasteland, human settlement, etc. Agriculture

is one of the major occupations in this region.

Coconut plantation is the dominant vegetation,

with paddy, red gram, groundnut, maize,

millets, tapioca, cereals, banana and papaya

are grown successfully as intercrops. It also supports intense shrimp farming

activities. The traditional system of shrimp farming is carried out on paddy fields

adjacent to the Vembanad lake (Pokkali fields).

Major Landuse categories as classified using IRS ID

Reclamation of Cochin Backwaters over the decades

Landuse/Landcover around Cochin

Backwaters

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The major landuse categories as classified using IRS ID satellite imagery are tabulated below.S.no Landuse / Landcover Area (sq.km)

1. Backwater 132.02. Built-Up area 133.03. Beach 4.54. Aquaculture 31.05. Fallow Land 7.07. Settlement & Vegetation Mixed 854.08. Agriculture (Paddy field) 4.59. Agri.Plantation 132.010. Waste land 12.011. Wetland 65.0

The results from the present study showing reduction in the Backwaters and increase in island areas are shown below.Toposheet Satellite data

(SOI, 1981) (IRS IC, LISS III)

Backwaters 157.00 132.00Vypeen island 51.49 56.02Vallarpadam 2.85 4.23Bolghatty 2.61 2.34TOTAL 213.95 194.59

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Cochin Backwaters has been experiencing high level of anthropogenic pressure during the last five decades. The area of Backwaters in 1912 was 315 sq.km which has shrunk to 157 sq.km during 1989 (SOI Toposheet). As per the satellite data of 1998 it has reduced to 132 sq.km. Large areas have been reclaimed for harbour and urban development. The reclamation of Cochin Backwaters over the decades for various purposes is given below.

PERIOD AREA RECLAIMED PURPOSE (ha)

1834-1903 2227 Agriculture1912-1931 5253 Agriculture1920-1936 364 Willington Island1941-1950 1325 AgricultureTill 1970 5100 Paddy-cum-shrimp Culture1970-1984 800 Paddy-cum-shrimp culture1975 6900 Bunding at Thannirmukham1978 11 Fishing harbour1981-1985 142 Vallarpadam-Ramanthuruthu, Candle Island1981-1985 142 Southern extension to Willington Island1981-1985 24 Urban development1981-1985 12 Cochin Shipyard and tanker berth

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TEMPERATURETEMPERATUREThe average atmospheric temperature ranged from 23.8° C to 34.52° C with minimum and maximum values in January and May respectively.

HUMIDITYHUMIDITYThe average relative humidity values varied from 77.09% in January to 93.66% in September.

RAINFALLRAINFALLThe climate is typical of tropical areas. The average monthly rainfall (south-west monsoon) during 1998 ranged from 5 mm in March to 649 mm in September and the rainfall from the north-east monsoon was negligible.

TIDESTIDESCochin estuary has a perennial connection with the Arabian sea near the main entrance of Cochin harbour. This region is subjected semi-diurnal tidal influencewith a maximum range of about 1m.

CURRENTCURRENTThe maximum speed of the flood current varied from 1 to 1.5 knots, while the ebb current always have a greater intensity and during the monsoon months it varies from 2.5 to 3.5 knots.

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The salinity in Cochin Backwaters varied

across three distinct periods in an year (i) a

period of low salinity (June-September), (ii)

a period of gradual rise in salinity (October

-January) and (iii) a period of high salinity

(February to May). The low values were

observed in Backwater region and high

values in neritic zone (near barmouth).

During south-west monsoon, the entire

Backwaters became a freshwater zone

barring the barmouth. In neritic zone (near barmouth) there was a

stratification in the surface layer with a low salinity and bottom layer with a high salinity, showing an increase in

salinity with depth.

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The dissolved oxygen content of thesurface water did not show much

fluctuation though realtively higheroxygen values were found during themonsoon season. DO in the surfacewaters varied from 3.9 to 5.27 mg/l

(pre -monsoon), 3.59 to 5.39 mg/l

(monsoon) and 3.44 to 5.59 mg/l (post

monsoon).

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The water column has maximum

suspended materials during the

monsoon period, but this quantity

declines progressively during the

post-

monsoon and pre-monsoon months.

Short-term changes induced by the

tidal currents are quite large and

during the pre-monsoon and post-

monsoon months the total material

transported from sea into the

backwater amounts

approximately to 900 tonnes/day.

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Nitrite

The nitrite concentration ranged from 0.20 to 1.63 in pre-monsoon, 0.14 to 1.27 µmol/l in monsoon and 0.07 to 0.4 in post- monsoon season.

Nitrate

Nitrate content in water varied from 5.25 to 11.8 in pre-monsoon, 0.80 to 7.86 umol/l in monsoon, and 0.92 to 19.16 in post-monsoon. The concentration of nitrate was high in estuarine zone compared to neritic environment due to fresh water input in the backwater region.

Phosphate

Phosphate content varied from 1.02 to 4.92 umol/l in pre- monsoon, 1.84 to 17.7 µmol/l in monsoon and 0.44 to 3.29 in post-monsoon season.

Silicate

Silicate content varied from 62.87 to 410.78 µmol/l in pre-monsoon, 139.6 to 717.4 in monsoon and 5.7 - 51.0 in post-monsoon period.The concentration of nitrate, nitrite, phosphate and silicate exhibited pronounced

seasonal variation and also indicated large inputs from industrial units, sewage waste and agricultural run offs. On the northern parts of the estuary high values during monsoon suggests the presence of an external input source.

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Petroleum hydrocarbon values recorded

in the Cochin Backwaters ranged from

0.09 – 70.23 gm/l in monsoon season

and 6.65 – 17.9gm/l in the post-

monsoon season. The maximum values

were recorded during monsoon season

at the barmouths of Cochin (42.92

gm/l) and Azheekodu region (70.23

gm/l). This is associated with shipping,

fishing vessel operation, transportation,

urban run-off, accidental spillages

during tanker operations, etc.

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As per the Environmental (Protection) Act, 1985 (29 of 1986), the Cochin Backwaters have been classified under the “Ecologically Sensitive Zone. In the following table the water quality of Cochin Backwaters is compared against the standards set for the SW-I waters by Ministry of Environment

and Forests.S.No

1.

2.

3.

4.

5.

Hydrological Parameters

pH range

Dissolved Oxygen

Suspended Solids

Lead

Cadmium

Standards setby MoEF

6.5 – 8.5

3.5 – 5.0 mg/l

None from sewage and industrialeffluents

0.01 g/l

0.01 g/l

In CochinBackwaters

6.5 – 8.6

3.44 to 5.59 mg/l

3.3 – 35.16 mg/l

0.008 g/l

1.26 g/l

Remarks

Within permissible limits

Within permissible limits

High values observed due to Sedimentation, sewageand industrial effluents predominantly in theCochin Barmouth area

Very high values observed in the Cochin Harbour area

Very high values observed in the Cochin Harbour area

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Cochin Backwaters support diverse species of flora and fauna. Totally 685 species of flora and fauna comprising 194 species of Phytoplankton, 135 species of zooplankton,199 species of benthos, 150 species of fishes and 7 species of mangroves were recorded between 1958 and 1997.

BIODIVERSITY – REVIEW OF LITERATURE

GROUP No. of species recorded

(1958-1997) PHYTOPLANKTON 194 ZOOPLANKTON

Coelenterata 39Cladocera 4Copepoda 47Ostracoda 7Mysidacea 2Cumacea 2Tanaidacea 2Isopoda 1Amphipoda 7Decapoda 16Chaetognatha 5Tunicata 1Molluscan larvae 2

GROUP No. of species recorded

(1958-1997)

BENTHOS Foraminifera 52 Coelenterata 6 Polychaeta 64 Crustacea 48 Mollusca 29

PISCES 150

MANGROVES 7

TOTAL 685

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In the current study (1998-99), 123 species of phytoplankton were recorded, comprising 89 species of Bacillariophyceae, 31 species of Dinophyceae, 2 species of Chlorophyceae and one species of Cyanophyceae. The density of phytoplankton varied from 33 to 10275 cells/l in estuary and 34 to 395 cells/l in neritic zone. The species diversity of Phytoplankton varied in estuarine and neritic regions. The dominant species were Asterionella japonica, Bacteriastum delicatalum, B.elongatum, B. hyalinum, Biddulphia mobiliensis, Pleurosigma sp, Thalassiosira sp, Chaetoceros, Coscinodiscus, Dinophysis, Fragilaria, Noctiluca, Oscillatoria, Pediastrum and Volvox. During pre-monsoon, the phytoplankton production in the estuary was high and fairly stable. During monsoon the flora was mostly freshwater species of the genera Pedorina, Volvox, Pediastrum and Desmedium. During post-monsoon gradually the freshwater species disappear coinciding with the predominance of marine forms.

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-

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In the present study (1998-99), 24 species of Zooplankton were recorded, comprising 14species of Calanoida, 2 species of Cladocera, 3 species of Cyclopoida, one species each of

Amphipoda, Aphragmophora, Cydippida, Decapoda, and Myodocopina. The copepodsconstitute one of the dominant taxa of zooplankton. Both diversity and abundance of thezooplankton were high during pre-monsoon and post-monsoon seasons. The dominant

speciesof copepods are Sapphirna, Eucalanus, Acartia, Acrocalanus, Classocalanus, Oithona,

Pseudodiaptomus, Paracalanus and Limura, sp.

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In the present study (1998-99), 24 species of benthic organisms were recorded in estuarine and neritic zones of Cochin Backwaters. The qualitative distribution of macrobenthos is given below:

Groups Monsoon Post-Monsoon Pre-Monsoon OverallEstuarine Neritic Estuarine Neritic Estuarine Neritic

Crustacea 2 - 4 - 3 1 5Polychaeta 7 5 9 9 9 10 16Bivalves - - - 1 1 2 2Echinoidea - - - - 1 - 1

In the past, 92 species were recorded, comprising 33 species of polychaetes, 28 sp. of crustaceans and 15 species of molluscs. The nature of substratum is another important factor in the distribution of macrofauna where clay bottom (organic matter 1.5-6%) supports poor fauna, whereas areas with sand, silt and clay in equal proportions support dense and diverse benthic populations. However, during the present study restricted to only one year, only a few species were recorded.

Distribution of benthic fauna in Cochin BackwatersDistribution of benthic fauna in Cochin Backwaters

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• Totally 150 species of fishes belonging to 100 genera under 56 families were identified from Cochin Backwaters. The fish which inhabit the different zones of the estuary are oligohaline (23 species) and the truly estuarine fishes (38 species). Fishery Resources as recorded from the landing centres is given in the Table.

(Catches in Kg)

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Fishing in the Cochin Backwaters is done by using an incredibly complex array of fishing gears. The operation of different types of gear starts from post-monsoon season and attains its peak during the pre-monsoon season. Stake nets and

dipnets accounted for 73% of the total landings. The contribution from gill

nets, seines, castnets and other indigenous fishing methods are 10%,

4%, 2% and 11%

respectively. Stake nets and dipnets are almost

confined to the northern sector (Cochin

estuary). The major part of the landings is

obtained from gill nets (34%), seines (25%)

and cast nets (19%).Chinese dipnet

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Shrimps form a major constituent of themarine fish landing in India. Of this, a

majority of penaeid shrimp is harvestedfrom the Kerala coast. In the estuarine and

backwaters of Kerala, M.dobsoni is thedominant species contributing to the

capture as well as the traditional culturefisheries. The following species of shrimps

are common. They are Metapenaeus dobsoni, M. affinis, M. monoceros,

Penaeusindicus, P.semisulcatus, P.monodon ,

P.canaliculatus, Acetes indicus and

A.erythraeus.

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Cochin Backwaters also support rich crab

fisheries. The economically importantspecies are Scylla serrata (mud crabs),

Portunus pelagicus and P.sanguinolentus,

which constitute 4% of the exploitedfishery resources of Cochin Backwatersyielding an annual production of 25.5,22.01 and 10.5 tonnes, respectively.

Crabs are obtained as by-catch in shoreseines, boat seines, gill nets, cast nets,

drag nets and stake nets used for finfishes.

Scylla serrata

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The molluscan fishery of the CochinBackwaters is exclusively sustained by theblack-clam Villorita cyprinoides. The other

dominant species like V.cyprinoides var Cochinnensis, V.cyprinoides var

delicatula,V.cornulopia, Meretrix meretrix, M.casta var

ovum and Paphia malabarica are also distributed in the Cochin Backwaters. The

peak clam landing is registered during the months of May and October.

However, the exploited clam resources show a declining trend over theyears; This is attributed to the increased and

indiscriminate fishing practices resulting in

disturbances in spat settlement, mass removal

of the undersized clams, and pollution hazards

from coconut husk retting grounds andindustrial pollutants.

Meretrix meretrix

Villorita cyprinoides

Paphia malabarica

Katelysia opima

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In Kerala, the mangrove vegetation isfound in Cochin, Vembanad, Quilon,

Trivandrum, Cannanore, Kozhikode andKottayam covering an area of 16 sq.km,of which 6.9 sq.km is in and around the

Cochin Backwater region. Mangrovespecies occur sparsely on the islands ofVypeen, Vallarpadam, and Bolghatty.

The dominant mangrovespecies in Cochin Backwaters are

Avicennia marina, A.officinalis, Exoecariaagallocha, Clerodentron sp., Aegicerascorniculatum, Rhizopora apiculata and

Acanthus ilicifolius.

Mangroves

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1.Reclamation of backwaters for various developmental purposes

2. Construction of Thannirmukham bund

3. Siltation

4. Sewage disposal

5. Pollution due to coconut husk retting activities

6. Industrial pollutants

7. Over-exploitation of resources.

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For conservation and management of these habitats and sustainable development of resources , the following are recommended :

•Strict enforcement of the fisheries regulation to cover the seasonal and mesh size restrictions.

•To regulate and monitor industrial pollution in Periyar river bed.

•To ban the collection of natural shrimp seed and under sized clam.

•Sea ranching of commercially threatened species like clams (Villorita cyprinoides and Paphia malabarica) for sustainable utilisation.

•Conducting of training and awareness programmes to coastal communities for community based resource management.

•To update the fishery regulation from time to time on scientific basis.

•To control the reclamation activities & sewage disposal in and around the backwater region.

•To regulate and monitor coconut husk retting activities in the Cochin Backwaters.

This Information system can be used as a baseline to conduct monitoring of biodiversity in future. Studies show that there is a decrease in the backwater area and floral and faunal diversity due to anthropogenic

effect and increased human activities like construction of dams, barriers, reclamation etc. However, long-term

studies on shore-line changes, bathymetry and biodiversity, etc need to be carried out using effective

standard methodology to supplement the basic information provided in the information system. This information system developed using remote sensing and GIS has demonstrated that these scientific tools

could be effectively used for monitoring and management of coastal resources of the Cochin

backwaters.

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