Sewagefed aquaculture system

SEWAGE FED AQUACULTURE SYSTEM MR. MONJIT PAUL & MRS. MUKTI CHANDA

[email protected]

Sewage fed aquaculture system Mr. Monjit Paul & Mukti Chanda

Asutosh College, Kolkata

GLOSSARY:

Batam cake: Local fish feed or nut oil cake.

Bati: Vessel used for measuring quantities of hatchlings.

Bheri: Earthen pond used for fish production.

Dallal: Agents and fish availability/quality informants used in

establishing and securing the transactions of fish of all life stages between

two parties.

Earthen hapa: Small shallow earthen pond used for holding fish.

Golder: Trader who transports large quantities of fish seed by truck

(owned or hired).

Golder employee: Sometimes permanent but usually seasonal employees

of golders involved in husbandry of fish seed during transportation in

truck and from truck to purchasers’ facilities.

Hapa: Nylon net cage used for holding fish.

Mahua cake: Distillation residue of the fruit (Manileara indica) used as a

natural pesticide in pond preparation.

Hundi: Small aluminum vessel used for transporting fish (also known as

patil in Bangladesh).

Patil Wallah: Independent trader who transports small quantities of live

fish and seed in hundies, usually on foot, bicycle / rickshaw or public

transportation (buses / trains).



INTRODUCTION:

The fish farmers of Kolkata developed a unique technique of

utilization of domestic sewage for fish culture long back in 1930s. The

early inspiration of utilizing the sewage for fish culture emerged from the

waste. Stabilization pond used as water source of vegetable fields. This

technique is considered to be the largest operational system in the world

to convert the waste in consumable product.

The growing fish demand of the metro city Kolkata is widely

met by this technique. In the course of time the area under sewage-fed fish

culture reached up to 12,000 ha. But recently due to rapid and

indiscriminate urbanization it has come down to 4,000 ha (approx)

resulting in crisis of livelihood of rural people. There are appeals to

Government to declare the existing sewage-fed aquaculture area as

sanctuaries.

However, even today, a considerable amount of fish consumed

in Kolkata city is produced from this system. There are appeals to

Government to declare the existing sewage fed aquaculture area as

sanctuaries and to protect them from further encroachment by the rapidly

expanding population of Kolkata city. The waste recycling system that has

evolved in Kolkata city involves garbage based vegetable farms,

wastewater fed fishponds, paddy fields using fish pond effluent and

sewage fed brackish water aquaculture.

The system is based on domestic sewage mainly and it is an

extensive or semi intensive type of aquaculture. The farmers generally

utilize treated sewage water to culture the organisms. No fertilization or

feeding in the culture pond is practiced, because the raw sewage is

nutrient rich and can enhance the growth of plankton production.

The culture system is also integrated type with duck, hen,

goat, pig or buffalo farming to meet the protein demand in the city.

Production of vegetables and flower is also done based on the raw sewage.



OBJECTIVES OF OUR TRAINING PROGRAM

This study was primarily undertaken to describe and analyze the

current production of freshwater fish in West Bengal, India by wetland

culture practices and its distribution within the state. Important

objectives of the work were to assess current practices, trends and

constraints within the system and to identify areas of improvement to

enhance the prospects of its future sustainable development and to

enhance our skills in the area of practical field. Industrial Fish and

Fisheries is a part of natural science, which needs practical exposure.

The study also help to improve the knowledge on fish culture

practice, sustainable development of our state and also our country by fish

production, utilization of wetlands for protein production, and

improvement of socio-economical condition of the weaker sections of the

community (fish farmers) through cheap and semi intensive methods of

fish farming by organizing a cooperative society. We gather all the

knowledge about the above, but theoretically all the college lectures, but it

is not enough for natural science. So at the end of 3rd Year we gather

knowledge about them practically. This training program also helps to

give the idea about the culture method by simple applied theory.

The wetland culture practice is the unique feature of Kolkata. The

wetlands area to the east of Calcutta is a large consumer of fish seed and

makes a significant contribution to food-fish supplies for local city and

rural populations.



PURBA KOLKATA MATSYAJIBI SAMABAYA SAMITY LTD.

The “Purba Kolkata Matsyajibi Samabaya Samity Ltd.” is one of the

cooperatives started in 2005 with the support of the government. The

society is situated in Eastern Kolkata, Tiljala, in South 24 Parganas

behind the building of Ruby Hospital and Srachi Tower (Emami Tower).

This society is formed by the weaker section of fish farmer who can not

earn by investing their own money.

The Society has 120 members with 3 female members. A

Management committee consisting of nine members manages the Society.

Elections are held once in three years. The Secretary of the Society can

work in that position for only 3 years. This demonstrates the high-level of

confidence created by the leaders through their completely transparent

system of management and provision of equal benefits to all members.

Every member of the society takes part actively in the work and activities

of the society and thereby conflicts are avoided.

The Society owns water area covering about 48 ha or 360 bigha of

land, with total number of 108 ponds. The society has 28 nursery pond and

80 stocking pond. The Society has a number of assets like nets, boats and

trucks, which are required for the efficient operation of the farm.

The farm earns Rs. 10,000/day. Each member receives a financial

benefit of Rs. 2,000 - 2,500 /month or Rs. 80/day along with a weekly paid

holiday, annual festival bonus and special holidays. Members are also

given limited medical reimbursement facilities. The annual transactions of

the Society are large in magnitude with financial transaction. This is a

huge sum in the local context and there is lot to learn from these

successful cooperatives.

The Society uses its own labor force for harvesting fishes and

marketing them in live condition. Several aquaculture management

practices are adopted by the Society.



The major expenditure of the farm is on some sewage fed farms also

integrate with pig farming, goat farming, buffalo, duck farming and hen

farming. Though due to the bird flue disease outbreaks in recent days, the

duck and hen farming is avoided. The farm is also integrated with

horticulture and vegetable culture.

The sewage fed system is threatened by the increasing

urbanization. Note the multistoried commercial complexes behind the fish

ponds. Procurement of seeds from hatcheries since the farm produces only

common carp and tilapia seed on site.

Fish are harvested continuously almost three times everyday

throughout the year, except for a month break in the whole year.



The Farm (Purba Kolkata Matsyajibi Samabaya Samity Ltd)



CHAPTER I:

SEWAGE:

Definition of Sewage:

Sewage is defined as a cloudy fluid arising out of domestic,

municipal and industrial waste, containing mineral and organic matter in

solution or having particles of solid matter floating, in suspension, or in

colloidal and pseudo-colloidal form in a dispersed state. Sludge differs

from sewage in that it is the solid portion of waste and does not include

fecal matter urine.

Fish and Sewage:

Wastes, including sewage and waste water produced by human

community hold high potentials for boosting fish production. The usual

high density of plankton and consequent die-off in sewage water ponds is

controlled and water quality improved by stocking with fish which graze

upon and utilize the dense plankton population in such ponds. Thus,

increasing importance is recently being given to enhance aquaculture

production through sewage utilization. Very high productions have been

obtained in India.

Composition of sewage:

Sewage may vary considerably in composition and strength from

place to place. The strength of sewage is determined by the amount of O2

required to oxidize completely the organic matter and ammonia present in

it. There is also variation in composition between domestic and industrial

sewage, the later containing more pollutants in terms of heavy metals and

bacterial load and other toxic ingredients. While the sewage is very rich in

anaerobes when it is raw but gradually transforms to an enriched

freshwater when it undergoes treatment. Sewage contains living matter

especially bacteria and protozoa. The water content of sewage may be 98 –

99.9 %, rest being dry solid matter. Domestic sewage has been reported to



contain about 250 – 400 ppm of organic carbon and 80 – 120 ppm of total

nitrogen, thus giving the C and N ratio of around 3:1.

Common characteristics of Kolkata city (raw) sewage:

pH: 6.8 – 7.8, CO2: 10 – 140 ppm, Dissolved O2: almost zero, Total

alkalinity: 170 – 490 ppm, Nitrates-N2: 0.01 – 0.6 ppm, Nitrite- N2: 0 –

0.08 ppm, Free ammonium- N2: 12 – 63.6 ppm, Albuminoidal ammonium-

N2: 1.1 – 16 ppm, BOD: 100 – 500 ppm, Phosphate (as P2O5): 0.12 – 14.5

ppm, Suspended solids: 160 – 420 ppm, Settle-able solids: 1.6 – 2.8 ppm,

Organic Carbon: 24 – 88.8 ppm. Gases like CO2, H2S, and NH3 etc. are in

dissolved state. The raw sewage is detrimental to fish and to make it

suitable for aquaculture or for usual disposal to the river, treatment is

necessary.

TREATMENT OF SEWAGE:

1. Primary treatment: This is mostly the physical removal of solids by

mechanical means. The solid material is removed by screening (for

larger coarse particles), skimming (for floating solids) and

sedimentation (for suspended particles whose density is greater than

that of liquid) techniques.

2. Secondary treatment: Soluble organic and inorganic matter, namely

the carbohydrates, proteins, fats, hydrocarbons and other nitrogenous

materials which are degraded mostly biologically, using

microorganisms into the smaller constituents i.e. CO2, H2O, NO3, NO2,

SO4, PO4 etc. which can be easily disposed. Sometimes chemical and

physical removals of substances are combined with this to increase the

effectiveness. There are three basic methods for secondary treatments:

activated sludge (flocculation), biological filtration and waste

stabilization. In the activated sludge or flocculation process, the

sewage is aerated by diffused air or by mechanical means. The

activated sludge (or biological floc) contains the microorganisms that

remove the soluble and insoluble organic matter in the sewage by a



combination of adsorption and oxidation or assimilation. Aeration

supplies the sludge microorganisms with oxygen and keeps the floc in

suspension. After a suitable contact time (1 – 20 hrs) the sludge is

separated from the sewage effluent in a settling tank. Some of the

settled sludge is returned for aeration along with new sewage but

most of it is treated separately in a sludge treatment plant.

3. Tertiary treatment: This is biological and chemical removal of soluble

products of partial or complete oxidation. For example, removal of

NO3, NO2, SO4, PO4 etc.

4. Quaternary treatment: Physical or chemical removal of refractory

organic or other substances which may be unpleasant and even toxic.

Chemical treatment comprises of (a) Coagulation or chemical

precipitation (e.g. by alum) (b) Deodorization (by Cl2, FeCl3) and (c)

disinfections or sterilization (by Cl2, CuSO4, liming etc.).

The process generally adopted for the use of sewage treatment before

release in fish ponds are:

(1) Sedimentation (2) Dilution and (3) Storage

(1) Sedimentation: The function of sedimentation is to remove suspended

solids from sewage to the maximum possible extent. It is done by letting

sewage into a pond/tank at a high velocity of flow. Sedimentation results

due to sudden drop in velocity when sewage enters a large pond from

sewage channel. Sedimentation is best carried out by in two successive

stages i.e. primary and secondary. The primary stage is intended to settle

down most of the heavier solids while the secondary stages serve two

purposes: (a) Provision of additional period to help to mix and homogenize

variations in the flow and (b) Promotion of natural purification process. It

has been estimated that about 33% BOD is got rid of by sedimentation

process, which may effect with 90% settlement of suspended solids and

about 25% reduction in albuminoid ammonia.



(2) Dilution: Before introduction of sewage into any fishery its dilution by

freshwater should be so effected that a positive dissolved oxygen balance

(1:1 or 1:2) is maintained and the concentration of unwholesome

ingredients such as CO2, H2S, NH3 etc. kept below lethal limit. The oxygen

required for biochemical reaction is obtained from fresh water used for

dilution and through green algae, and other vegetation in the water body.

Sewage is stored here for few days.

(3) Storage: The biological processes carried out by microorganisms

present in the raw sewage oxidize it.

Use of oxidation ponds (waste stabilization ponds) for sewage-fed

fish culture has been suggested by many several workers. The term waste

stabilization ponds is applied to a body of water artificial or natural

employed with the intention of retaining sewage or organic waters until

wastes are rendered inoffensive for discharge into receiving waters or on

land through physical, chemical and biological process (self purification).

This pond is suitable in India because of plentiful of sunshine. These are

also cheap to construct and easy to operate. Organic matter contained in

the waste is stabilized and converted in the pond into more stable matter

in the form of algal cell, which find their way into the effluent. These

ponds are of three types:

a. Anaerobic ponds: It is pretreatment digester and requires no

dissolved oxygen. These are designed to take on higher organic

loading so that anaerobic condition prevailed throughout the pond.

Such ponds are 2.5 – 3.7 m deep. Ends products are CH4, H2S, and

NH3.

b. Aerobic ponds: These are shallow, depth is 0.3m or less, so designed

that growth of algae through photosynthetic action is maximized.

Waste material is stabilized through microorganisms only and

aerobic condition is always maintained. Ends products are CO2,

H2O, NO3, SO4, PO4 etc.



Sewage Canal

Sewage Treatment (Mechanical Process)

Biological Treatment of Sewage



c. Facultative ponds: These are 0.9 – 1.5 m deep and are aerobic

during day hours as well as for some hours at night. Only for few

remaining hours of night, bottom layer become anaerobic. Aerobic,

anaerobic and facultative may all be found in a facultative pond. In

India, most of the waste stabilization ponds are of facultative type.

The village ponds and natural depressions in rural areas are

example of waste stabilization ponds.

A conventional oxidation pond retains the settled sewage at a depth

of 1 to 2 m (facultative ponds) for a period of 25 to 30 days. This pond

contains the algal-bacterial cultures, which oxidizes the organic matter

into CO2, H2O, H2S, NH3 and other decomposition products that are used

as nutrients (e.g. NO3, SO4, PO4). If this type of ponds are designed well

and operated effectively, well over 90% of the BOD is removed and the

micro flora is much reduced.

Simple Flow Chart of the Treatment of sewage:

Fish Culture with Sewage



Sluice Gate to prevent the entry of wild fishes and prevents the escape of cultured fishes

in pond

Open channel through which sewage is flown in the pond.



Draining of Pond by pumping

Drying of Pond

Silt is removed at least once in three years



Aquatic Weeds (It can be used as biological filters)

Dried water hyacinth is kept in heaps in the ponds for decomposition (manuring)



CHAPTER II:

SEWAGE-FED SYSTEM:

The sewage fed ponds, which are locally called “Bheries”. Although

these sewage-fed ponds are generally shallow and vary from 50 cm to

150cm in depth.

This system covers some 3000 hectares and comprises of 154

fisheries (bheries) which produce 13000 tonnes of food-fish per year, of

mainly IMC and tilapia, which are sold in nearby Calcutta markets,

representing 16% of fish sales in the municipality (Bunting et al., 2001).

The environmental ‘setting’ and system utilized for production in the ‘East

Calcutta Wetlands’ is quite unique; fisheries utilise some 550000m3 of

untreated wastewater per day (Edwards & Pullin, 1990), of primarily fecal

polluted surface water and sewage water from Calcutta, via canals and a

series of tributary channels. These wastewater nutrifies ponds, enhancing

natural phytoplankton, zooplankton and benthic fish food sources, having

economic benefits. Despite this input, inadequate wastewater supply has

been identified as a limiting factor (Bunting et al., 2001) with 15% of bheri

owners perceiving it as a problem (Kundu, 1994). Authority control over

wastewater distribution to the wetlands, pumping station maintenance

problems and sluice gate operation regulation problems result in

unpredictable sewage supplies, (Bunting et al., 2001) which are

compounded by the siltation of urban drainage systems and lead to

competition between those exploiting the resource (Kundu, 1994).

Species Cultured:

Although both Indian and exotic carps are grown, farmers have

specific preference for the Indian carps, namely catla (Catla catla), rohu

(Labeo rohita), mrigal (Cirrhinus mrigala) and bata (Labeo bata) with

bulk of the stocking consisting of mrigal. Exotic fish like silver carp

(Hypophthalmichthys molitrix), grass carp (Ctenopharyngodon idella) and

common carp (Cyprinus carpio) are stocked as a small percentage.



However, the popularity of tilapias (Oreochromis niloticus and

O.mossambicus) is increasing and they constitute 5-30% of the species

stocked with different ponds. There is also a tendency for some farmers to

stock Pangasius hypophthalmus to control mollusc populations and some

are attempting to culture high value species like giant freshwater prawn,

Macrobrachium rosenbergii.

Culture Technique:

The fish farmers of Kolkata operating sewage-fed fish fisheries,

however generally use raw sewage, relying on intuition and experience for

regulating its application. This practice is not only unhygienic but also

harmful since the sediment organic matter besides raising the bed level of

pond being highly oxidisable in character may undergo decomposition and

cause negative oxygen balance causes mortality. But sewage partly or

fully decomposed contains a high percentage of nitrogen, phosphorus, Ca,

K etc. These nutrients together with adequate alkalinity contribute

largely to a high productivity in sewage water and for this reason

fertilization of fishpond is sometimes carried out with raw sewage.

Channel feeding bheries with slick of black sewage, just discernible



The following techniques were adopted by the farmers:

1. Preparation of ponds

2. Primary fertilization

3. Fish stocking

4. Secondary fertilization

5. Harvesting of fish

Preparation of Ponds:

Pond preparation is undertaken generally in winter (Nov – Feb)

when the fish growth is reported slowest. Ponds are drained, desilted,

tilled and dried in sun. Sewage from the canal is drawn in to the pond and

allowed to stabilize for 15-20 days.

The liming is also done in this stage to control the pH of the bottom

soil and as well as to destroy the pathogens. Lime also helps to improve

the growth of the fishes. Lime is applied in the pond by checking its pH. If

pH is lower than 7, 50 to 80 kg of lime is often used in one bigha pond to

improve the pH.

The pond dikes are consolidated. Silt traps (perimeter canal along

the dikes) 2-3 meter wide and 30-40 cm. deep are dug, as they get filled

during regular harvesting of fishes.

There are about 100 plant species which have been recorded in and

around the East Calcutta Wetlands. These include Sagittaria

montividensis, Cryptocoryne ciliata, Cyperus spp., Acrostichum aureum,

Ipomoea aquatica, Typha spp., etc. Aquatic weeds as water hyacinth

(Eichhornia), algae, Ipomoea, duck weeds (Lemna) and algae with other

aquatic weeds are grown in the pond, though they can save the dikes from

wave, and give shelter to fishes against high temperature and poaching

and above all it extracts heavy metals from the sewage, supplies oxygen by

photosynthetic activity, the weeds must be removed for better

management of the farm. The weeds are removed by manually (hand



picking) or by weedicides like 2-4D and detergents. Biological control of

aquatic weeds is also practiced by extremely herbivorous fishes.

For raising carp seed, ponds are dewatered completely during

summer to remove all the carnivorous and weed fishes. When complete

dewatering is not possible treatment with mohua oil cake (distillation

residue of the fruit (Manileara indica) used as a natural pesticide) in pond

preparation or other similar fish toxicants are used. The oil cake turns

the water black, but after a few days the water become clear and residue

of the oil cake acts as the fertilizer of the pond.

The bamboo sluice gate is repaired which helps to prevent the entry

of unwanted fishes and escape of cultured fishes.

Primary fertilization:

After pond preparation, sewage is passed in to the pond from the

feeder canal through bamboo sluice. Initial fertilization of pond is done

with the introduction of fresh sewage effluent, which is taken into the

pond up to 90 cm. It is left to stabilize for 15 – 20 days.

The self-purification of sewage takes place in presence of

atmospheric oxygen and sunlight. When the water turns green due to

photosynthetic activity, the pond is considered ready for stocking.

Generally external fertilization is not used in the sewage fed farming

system. But the mohua oil cake acts as the fertilizer in the pond when

utilizes. The nutrients present in the sewage water are enough to fertilize

the pond and helps in the production of sewage.

Following this the ponds show extreme diurnal fluctuation of

dissolved oxygen ranging from super saturation stage at day time to

serious depletion in night. However, due to dilution and natural

putrefaction process, the wide fluctuation of dissolved oxygen is minimized

within a month and the pond rendered suitable for stocking and rearing

fish seed.



Fish stocking:

The photosynthetic activity in the pond is the basis for biological

purification of the sewage. Once the water turns completely green,

stocking of fish is initiated. Before stocking fish, some are kept in hapas in

the pond to test pond condition through survival. If the results are

positive, large scale stocking is undertaken. Fish stocking takes place

several times in a year depending on the intensity of operation.

All the species of Indian major carps e.g. Labeo rohita (Rohu), Catla

Catla, Cirrhinus mrigala (Mrigal) and Exotic carps e.g.

Hypophthalmichtys molitrix (Silver carp), Ctenopharyngodon idella

(Grass carp), Cyprinus carpio (Common carps) are preferred to be stocked

but the percentage of Mrigal is kept greater and that of exotic carps is

lesser. The popularity of Tilapia and fresh water prawn, Macrobrachium

rosenbergii is increasing these days. Pangasius hypophthalmus is also

stocked by some farmers to get rid of mollusks. As the sewage contains

high content of nutrient, the farmers keep very high stocking density, i.e.

40,000 to 50,000 fingerlings/ha.

Sewage-fed ponds are used for raising seeds of Carps and Tilapia

and also culturing them to table size The stocking density in such pond

varies from 70000 to 150000 per ha. The density is depended mostly on

the size of the spawn or fry. The preferable stocking density of the pond is

Catla 40% 72 mm/ 6 gm 133 mm/ 30 g, Rohu 6% 72 mm/ 5 gm 147 mm/ 37

gm, Mrigal 45% 74 mm/ 4 gm 126 mm/ 24 gm, Common Carp 9% 54 mm/ 3

gm 135 mm/ 50 gm.

For raising Tilapia seed more or less the same techniques as that of

carp seed are adopted. However, instead of Tilapia spawn/fry, adult

Tilapia of both sexes is stocked together in the ration of 6 males: 4 females

at about 20 000/ha. They bred profusely in the pond. The harvesting of

fingerlings is initiated two months after stocking of adults and is

continued periodically either fortnightly or monthly depending on the



density of harvestable size tilapia. Normally 30 – 40 gms Tilapia are

harvested. Tilapia was not found to be affected even at the highest

attained NH3-N level of 5.43 ppm. He got the production of 9350 kg/ha/yr

Secondary Fertilization:

After stocking, sewage is taken in ponds throughout the culture

period at regular intervals @ 1–10% of the total water volume of the pond.

In bigger ponds, water level is maintained by continuous inflow and out

flow. The requirement of sewage is determined by observing the water

color, transparency, temperature and depth. The sewage partly or fully

decomposed contains a high percentage of nitrogen, phosphorus, Ca, K etc.

These nutrients together with adequate alkalinity contribute largely to a

high productivity in sewage water and for this reason fertilization of

fishpond is sometimes carried out with raw sewage.

Fish Harvesting:

The bheri farmers have evolved rotational cropping system to

maintain the supply to the market. Fishes are stocked and harvested

throughout the culture period leading to periodical stocking and regular

harvesting. After completion of one phase, fishes are restocked @ 1 Kg

fingerlings per 5 kg harvested fish. Another harvest phase starts after 15

days of restocking. Generally, drag nets are used for harvesting by

encircling technique. Some fishes like Tilapia and Common carp require

hand picking technique for their harvesting. Specialized fishermen are

employed in fishing.

Cyprinus carpio



Netting Operation

Netting Operation

The Fish after Netting



CHAPTER III:

FARM MANAGEMENT:

Rationale Cropping System:

Farmers have evolved culture systems that are responsive to

market demand. Fish are stocked and harvested throughout the culture

period leading to periodical stocking and regular harvest. In larger ponds,

harvesting takes place continuously for almost fifteen days in a month.

After completion of one cycle of harvest in a large pond, fishes are

restocked at the rate of one kg of fingerlings for every five kg of fish

harvested. After restocking, fishes are left undisturbed for the subsequent

fortnight and harvesting will start again after that period. Drag nets are

commonly used for harvesting fishes through an encircling technique.

However, for the bottom burrowing and difficult to catch species

like common carp and tilapia, encircling with the net and hand picking are

adopted as common techniques. There are specialized people to harvest

fishes using these strategies.

Health Care:

The sewage-fed cultured fishes are most vulnerable to bacterial

diseases, but surprisingly the occurrence of bacterial or any other disease

is not common in sewage-fed fish farms. Even when EUS was prevailing in

recent years in other areas, the sewage-fed ponds were uninfected.

According to the farmer the diseases is vulnerable only in hygienic water.

When the diseased fish released in sewage pond, the disease is

automatically cured.

However, parasitic infections by Lernea (Anchor worm) and Argulus

(Fish lice), bacterial disease like fin rot or tail rot, fungal disease like gill

rot and skin ulcer are common but they are not given any proper

treatment. Fin rot tail rot gill rot or ulcer is common but theses diseases

are not creating any problems.



Generally there is no disease management is taken in the culture

pond. Liming is done periodically which can cure many diseases. But the

treatment of disease should be taken in the farm for better management.

Protection of Dykes:

Aquatic weeds like water hyacinth are grown along pond dikes of

larger ponds to break waves and prevent damage to dikes. In addition,

these weeded areas, provide shelter to fish when the temperature rises,

prevent poaching of fishes to some degree and most importantly serve as

filters to extract nutrients and metals from the system.

When these weeds grow in excess, they are periodically harvested

and decomposed in the pond to enhance fertility of water. Surrounding

these large ponds, silt traps 2-3 m wide and 30-40 cm deep are dug. These

get filled with regular harvesting of fishes. Farmers restrict themselves to

cleaning of these silt traps instead of digging the entire pond. Silt rich in

nutrients is used for various purposes, including strengthening of dikes.

Feeding of Fish

Generally the feeding of fish is not practiced in extensive type of

sewage-fed fish culture system.

But in semi intensive type culture system, feeding is practiced with

Mastered oil cake, Rice bran with 1:1 ratio. Nut oil cake, Coconut oil cake

are also used. The nursery pond fishes are fed with wheat flour. The

herbivorous fishes are fed with aquatic vegetation, aquatic weeds like

Lemna etc.

In pond, the waste food products like residues of human foods,

breads are also utilized. These foods are very good for Tilapia niloticus and

Tilapia mossambicus. The waste foods are taken from the hotels and

nearby bakery.



Mohua Oil Cake

Unknown Fish may have the Aquarium Importance

Algae in Pond



Clearance of Weeds



Different Types of Aquatic Weeds



CHAPTER IV:

NURSERY SYSTEM:

The seed of the fish species are brought the bheri from the outside

markets, but the nursery rearing of the seed is done here. A nursery is a

facility where fish seed (spawn, hatchlings or fry) can grow. Efficient

fishpond culture requires special preparation of nurseries for receiving

spawn and hatchlings. The ideal size of a nursery is 0.02-0.05 ha with a

depth of 1.0-1.5 m.

Fish Seed Supply:

Few independent nursery operations are present in the wetlands

which supply the bheries as the present bheri have their own nursery

ponds for rearing hatchlings and fry to fingerlings for stocking.

Hatchlings, fry and fingerlings are therefore distributed to the wetlands to

facilitate the needs of the producers. The system utilizes large quantities

of seed to support the scale of food- fish production, which are primarily

supplied by golders.

Most of the supply, which includes all life stages, comes from

hatcheries and nurseries in Districts to the north of Calcutta through

golders based in the wetland village markets, Chowbaga, Chingrihata and

Bantala who liase with dallals within production areas. Additional

supplies of hatchlings were identified to come from Bankura District

hatcheries through two golders based in Sealdah in Calcutta. Using

hundies in trucks and operating on a daily basis from April to July these

golders supply an estimated 240 million hatchlings to the wetlands. Local

patil wallahs make an additional small contribution to wetland seed

supplies. One patil wallah who was interviewed in the wetlands collected

fish seed from Naihati Seed Market and by using the train and bicycle

delivered fingerlings to Bamamghata Market in the wetlands. This

particular market was chosen by the patil wallah as the absence of golders

reduced competition, whilst being a fish market where producers sold



food- fish, offered opportunity for marketing and selling seed. Splashing

was frequently done to aerate the water prior to sale whilst the placement

of fish in a hapa in a nearby pond aided survival in the event of a delayed

sale.

Preparation of Pond for Nursery:

Remove all aquatic weeds or Drain and dry the pond.

Apply 5-6 kg lime/200 m² which helps release food nutrients

available and kills pathogenic organisms in the pond.

Refill the treated sewage water rich with nutrients. Generally no

fertilization is done.

The water left to increase the plankton population. To determine if

enough food organisms (plankton) for the fish fry have developed in

the pond, the most basic and reliable test involves filtering

approximately 50 liters of water through a fine mesh net or cloth

into a 2.5 cm diameter specimen tube. Alternatively, a very simple

field test in non muddy water is to dip one's hand in the water to

the elbow. If the hand is no longer visible, the plankton is probably

sufficient.

To kill the aquatic insects, oils are used. Sometimes diptrex are also

used to kill the aquatic insects.

To enhance the plankton production, raw sewage may be given with

required quantity to enhance the plankton growth in the pond

water.

Stock 60,000-70,000 hatchlings/200 m² of 4-5 days age (200-250 g).

The hatchlings should be of same age, uniform size, vigorous and

released either in morning or late afternoon (day 30).



Fish Seed in Nursery Pond

Preparation of Nursery Pond

Bati used to measure the quantities of fish seed



Golders in Sealdah with hatchlings destined for the wetlands

Patil Wallah splashing to aerate hundi water



Aquatic Insects



Removing of Aquatic Insects by using of Oil & Soap

Insecticide



CHAPTER V:

CULTURE OF TILAPIA IN THE BHERI

The most common species are Tilapia (Oreochromis) niloticus and

Tilapia (Oreochromis) mossambicus cultured in the wetlands mostly.

These species are popular because of their high resistance power in any

condition of water, temperature and have good market value. The growth

rate of the fish is also good and the fish is omnivorous. The fish is mouth

brooders and can reproduce in any stagnant condition without any

induction.

Culture Procedure:

Mixed Sex Culture:

Mixed-sex populations of fry are cultured together and harvested

before or soon after they reach sexual maturity, thereby eliminating or

minimizing recruitment and over-crowding. A restricted culture period

limits the size of fish that can be harvested.

In mixed-sex culture, tilapia is usually stocked at low rates to

reduce competition for food and promote rapid growth. One month-old, 1-

gram fry are stocked at 2,000 to 6,000 per acre into grow out ponds for a 4-

to 5-month culture period with total production is near 700 kg/acre for a

stocking rate of 4,000/acre. Expected survival is roughly 70 percent.

Two to three crops of fish can be produced annually in the tropics

compared to only one crop in temperate regions. In temperate regions,

mixed-sex culture is referred to as young-of-the-year culture because fry

produced in the spring are grown to marketable size by autumn. Early

spawning is needed to maximize the grow-out period.

Male Mono-sex Culture

Males are used for mono-sex culture because male tilapia grows

faster than females. Females use considerable energy in egg production



and do not eat when they are incubating eggs. Male mono-sex culture

permits the use of longer culture periods, higher stocking rates and

fingerlings of any age. High stocking densities reduce individual growth

rates, but yields per unit area are greater. If the growing season can be

extended, it should be possible to produce fish weighing one pound (454

grams) or more. Expected survival for all-male culture is 90 percent or

greater. A disadvantage of male mono-sex culture is that female

fingerlings are discarded.

The percentage of females mistakenly included in a population of

mostly male tilapia affects the maximum attainable size of the original

stock in grow-out. For example, manually sexed T. nilotica fingerlings (90

percent males) stocked at 3,848/acre will cease growing after 5 months

when they average about 0.8 pounds (365 grams) because of competition

from recruits. If larger fish are desired, females should comprise 4 percent

or less of the original stock and predator fish should be included.

The stocking rate for male mono-sex culture varies from 4,000 to

20,000/ acre or more. At proper feeding rates, densities around 4,000/acre

allow the fish to grow rapidly without the need for supplemental aeration.

About 6 months are required to produce 500-gram fish from 50-gram

fingerlings, with a growth rate of 2.5 grams/day. Total production

approaches 2.2 tons/acre.

A stocking rate of 8,000/acre is frequently used to achieve yields as

high as 4.4 tons/acre. At this stocking rate the daily weight gain will range

from 1.5 to 2.0 grams. Culture periods of 200 days or more are needed to

produce large fish that weigh close to 500 grams. To produce a 500-gram

fish in temperate regions, overwintered fingerlings should weigh roughly

70 to 100 grams and be started as early as possible in the growing season.

A stocking rate of 8,000/acre does require nighttime emergency aeration

when the standing crop is high.



Stocking rates of 12,000 to 20,000/ acre have been used in 1.2 to 2.5-

acre ponds, but this requires the continuous use of two to four, one-horse

power paddlewheel aerators per pond. Yields for a single crop range from 6

to 10 tons/acre.

Poly Culture of Tilapia

Tilapia is frequently cultured with other species to take advantage

of many natural foods available in ponds and to produce a secondary crop,

or to control tilapia recruitment. Poly-culture uses a combination of

species that have different feeding niches to increase overall production

without a corresponding increase in the quantity of supplemental feed.

Poly-culture can improve water quality by creating a better balance

among the microbial communities of the pond, resulting in enhanced

production. The disadvantage of poly-culture is the labor intensive to sort

the different species at harvest. The role of natural pond foods is less

important in the intensive culture of all male populations and may not

justify the expense of sorting the various species at harvest.

Tilapia can be cultured with Indian Major Carps and as well as

exotic carps. The carnivorous fishes like Murrells can be cultured with

tilapia, which can grow by feeding of tilapia hatchlings and the over

crowding also can be avoided. Male tilapia stocked at a rate of 800/acre

yield nearly 770 pounds/acre when channel catfish are stocked at

3,000/acre.

Silver carp (Hypophthalmichthys molitrix), and grass carp

(Ctenopharyngodon idellus) at densities of 800; 1,000; and 20/acre,

respectively can be stocked with tilapia for poly culture system with no

additional feed.

Another promising poly-culture system consists of tilapia and

prawns (Macrobrachium rosenbergii). In poly-culture, survival and growth

of tilapia and prawns are independent. Feed is given to meet the

requirements of the fish. Prawns, which are unable to compete for the



feed, utilize wasted feed and natural foods that result from the breakdown

of fish waste. Stocking rates for 1 to 2 gram prawns vary from 4,000 to

36,000/acre, but a rate of 8,000/ acre is often used to obtain a high

percentage of market-size prawns (<25 grams) and a yield of about 445

pounds/acre. Tilapia can be stocked in the range of 2,000 to 4,000/acre.

Tilapia niloticus

Tilapia Culture Pond



Mouth Brooder Tilapia



Feeding

Fish Seed



CHAPTER VI:

INTEGRATED CULTURE:

The most impressive aspect of aquaculture that the study group

observed was the integration of fish farming with livestock production and

farming of agricultural crops, including vegetable farming. Integrated

farming is a traditional, has in recent years been further supported by the

concept of an all-round 'development of agriculture, animal husbandry,

fisheries and other sideline occupations. Although integrated farming is

economically and environmentally sound, and can be used the area of

farms properly.

Nature of Integration:

The fish cultivated and the general farming practices are amenable

to easy integration, the grass carp feeds on grass and other vegetable

matter which can be grown on the dikes and adjacent agricultural land.

They also feed on aquatic plants which can be raised in canals and other

adjacent water bodies. Aquatic plants such as Pistia stratiotes, Eichhornia

crassipes, Alternanthera phyloxorides and duck weeds, are grown for

feeding fish or pigs and poultry on land. Bananas are some of the other

crops grown in association with fish farms. Ipomea aquatica, Lolium

perenne, sorghum, is also grown in many areas. The leaves, stalks or other

waste products are chopped or crushed and fed directly to the fish or

composted to be used as fertilizer. Silver carp and big head feed on

plankton which can be grown by the application of organic manures

provided by pigs, cattle, and chicken raised by the side of fish farms. As

mentioned, pigsties are often built on pond dikes, facilitating the

application of manure, either directly or after fermentation.

Duck and hen farming in association with fish, is also reported to be

practiced in a few places. The duck and hen farming meet the protein

production in the farm. Dropping of duck and hen can fertilize the ponds

additionally.



Goat and Pig farming is the next integration in the farm to meet the

protein production. Government also encourages the production of goat

and pig in recent days to avoid the problems of bird flue. The manure

produced by 20–30 pig in a year produce the same fertilization effect as 1

tone of ammonium sulphate applied to the soil. Collective as well as

individual pig rearing is promoted where the pigs are largely fed on

kitchen wastes, aquatic plants and crop wastes. The feeds for the pig are

mainly left over food from households, lettuce, rice bran, water hyacinth,

peanut cake, corn meal and soybean meal. Ducks, geese and chicken can

be raised on ponds. In fact, a well managed fish pond provides much

cleaner and healthier environment for ducks and pond-reared ducks are

generally free from parasites and diseases.

Vegetable Farming:

The open spaces of the farm are used as the vegetable farming. The

sewage effluents, waste product of the human community or the pond

bottom humus are used as the manure of the vegetable farming. One tone

of pond humus is equivalent to 6 kg of ammonium sulphate. Intensively

cultured pond produces about 52.5 tonnes of humus and silt/ha/yr which is

equivalent to 225 kg of urea. Besides the vegetable farming horticulture is

also practiced.

Different Aquatic Weeds



CHAPTER VII

REGULAR MANAGEMENT OF THE WETLAND CULTURE SYSTEM:

Transport and release of fingerlings are carried out during the

morning hours.

The fish stocked are checked at the monthly intervals for their

growth and health through sample netting.

Inflow of sewage (2 million lit/ha/day) and dilution should be

regulated properly to keep the pond aerobic.

Regular monitoring of physico-chemical parameters

Regular cleaning of spun pipes interconnecting the treatment

pond and fishpond to ensure smooth flow of sewage effluents.

Equal splitting of effluent to the fishpond need to be ensured.

Wire mesh is to be provided at the entry of sewage effluent to

prevent the entry of solid materials into the treatment complex.

Proper sloping should be maintained at the entry point to

maintain the velocity of influent.

NEGATIVE ASPECT OF SEWAGE FED FISHERIES:

The sewage contains high load of organic and inorganic matters,

toxic gases but its dissolved oxygen contents is very low.

As the raw sewage is used in fish ponds, there is a chance of

infection and pollutions to enter into human body through fish. This

risk can be minimized if good managerial practice is followed, e.g.

Use of treated sewages for fish culture instead of raw sewage

Keeping the fish for 3-4 weeks in marketing pond (Clean fresh

water pond) before marketing

Large plastic containers are used in tricycles transportation of

fishes in live condition for the transportation of fish in live

condition

Aluminum vessels, called “hundies”, are used to transport seed as

well as live fish to market



To avoid these harms, a model of sewage fed fish culture techniques

is advisable in which the sewages is treated properly.

Ponds should be prepared and categorized as per the treatment

techniques.

Screening and Filtration of sewage is done to remove course

particles, before taking in to ponds.

Sedimentation of sewage is carried out in large tanks by

dropping the sewages with high velocity resulting in settlement

of suspended particles at the bottom. Chlorine and CuSO4

further treat the sewages for disinfection.

Oxidation should be done after sedimentation in

oxidation/stabilization ponds. Here the sewage is retained for 10-

12 days for self-purification in presence of sunlight and

atmospheric oxygen. Photosynthetic activity also occurs here. All

these result into reduction in CO2 and increase in oxygen level of

sewage.

Sewages are passed into duckweed tank where it is let for a few

days. The duckweed (Lemna, Wolfia etc.) and Eichhornia absorb

the heavy metals from the sewage and further increase the

oxygen level by their photosynthetic activity.

Finally, the sewages are taken in to fishery pond/storage pond

where it is diluted with sufficient quantity of fresh water. This

results in to reduction in CO2, H2S, NH3 and increase in DO2

level making the sewages perfect for fish culture.



Fishing Net

Crabs and Fishes

Snails



CHAPTER VIII:

MARKETING OF HARVESTED FISH:

Harvested fish from sewage-fed ponds are marketed in live

condition as they give high market price. Based on the market demand

different sized fishes are harvested and sold. The bulk of the harvested

fish consists of Indian major carps and tilapia. Specialists carry out

harvesting of fish in large ponds. Tilapia and common carp are largely

harvested through hand picking. Fishes of 100 gm wt. are called ‘Hotel

Fish’ as they are sold hotels. The fishes are transported to marketing

centers on bicycles, tricycles and trucks. Skilled persons, who get Rs. 40-50

for their 3-4 hours work, transport the fishes on bicycles. In addition to

food fish supplies the system sustains 17000 jobs.

Marketing of fish



Recent Problems due to Urbanization

Boat Used in Farm

Peri-urban dweller catching escaped fish from behri outflows



Labeo rohita

Catla catla

Cirrhinus mrigala



Macrobrachium rosenbergii

Sewage Canal



CONCLUSION:

The sewage fed culture is a cheap process of fish culture with no

manuring and supplementary feeding due to high content of nutrients in

the sewage. The method of utilization of water reduces the accumulation

of organic load in river systems. The sewage fed fish culture uses the

waste recycling process and maintains the good environment around the

urban area. Unfortunately, this system is being lost due to urbanization

without understanding its ecological, environment and economic benefits.

The system also dissipates large volumes of water reducing the risk of

flooding in the city which in the past has paralyzed life and economic

activity, however urban encroachment is threatening this resource, which

if continued will impoverish 2,00,000 people through loss of livelihoods

and flooding.

On a smaller scale, a local fisherman was encountered during

wetland visits that were identified as an indirect benefactor of production

by catching escaped farmed fish from bheri wastewater feeder channels in

the area (Figure 33). These fish, ranging from fingerling to occasionally

food- fish size, were either consumed or sold in local markets and provided

the fisherman’s only source of income. There appears to be a range of

socio-economic and environmental considerations in this area, which

potentially affect a number of sectors which therefore requires a

sustainable environmental management strategy.

The quality of fish grown in sewage fed remains as major concern,

but the prolonged practice and many scientific studies have discarded it.

An international seminar held in 1988 at Kolkata with the support of

UNDP, World Bank Water and Sanitation Program, ESCAP and Govt. of

India recognized the uniqueness of this Kolkata system and recommended

detailed study on existing practice and quality of fish grown.

It is a matter of concern that even after a long journey of these

important innovations, it has not spread to the other parts of the country.



Perhaps bringing farmers, specialist from the scientific and development

community to see this Kolkata practice might help in applying the system

elsewhere in country. The CIFA, Bhubaneswar and CIBA have reported

the development of an improved method of sewage fed fish culture avoids

direct use of raw sewage. Though there are fears about the safety of the

fish grown in sewage fed system, it is general belief in Kolkata that the

fish grown in sewage tastes better.

This has caused substantial amount of metal deposition in the canal

sludge and rendered the waste water incapable of ensuring the edible

quality of the fish and vegetable grown in the wetland.

The conservation area boundary for the East Calcutta wetlands and

waste-recycling region was mapped in 1985 by the State Planning Board,

Government of West Bengal. This wetland area is protected by order of the

Calcutta High Court in 1992, which prohibits change in land use. High

Court directed the State government to take recourse to statutory cover, if

required, to prevent any private alienation of land. Recently, the Director

of land and Land Records, Govt. of West Bengal has issued a fresh order

prohibiting any conversion of land use within the conservation area

boundary and declaring all such conversions that have taken place since

1992, as void. Filling up of water bodies in this area is not permissible

under West Bengal Town and Country (Planning and Development) Act,

1979 as well as under the West Bengal Inland Fisheries Act, 1984 (with

amendment in 1993).



REFERENCES:

Bunting, S.W., Kundu, N. and Mukherjee, M. 2001. Renewable natural

resource-use in livelihoods at the Calcutta peri-urban interface:

literature review. DFID. U.K. 37 pp.

Datta, S. (2007). PGDIF Class note on Sewage-fed Aquaculture.

Datta, S. and Pal, A.K. (2005). Environmentally sustainable management

techniques for sewage-fed aquaculture. In Biotechnology in

Environmental Management. Vol. 1. T.K.

Edwards, P. and Pullin, R.S.V. (edts) 1990. Wastewater-fed Aquaculture,

Proceedings of the International Seminar on Wastewater Reclamation

and Reuse for Aquaculture, Calcutta, December 1988. Bangkok,

Thailand: Asian Institute of Technology, Environment Sanitation

Information Center. 87 pp.

FAO, 2002. Fishstat plus, Aquaculture production database. Fisheries

Information, data and statistics unit, Food and Agr. Org., Rome

Ghosh, T. Chakraborti and G. Tripathi (Eds.) p. 339-350. A.P.H.

Publishing Corporation, New Delhi.

IDNR (Illinois Department of Natural Resources) 2001. Snails. Illinois

Department of Natural Resources.

http://dnr.state.il.us/orep/inrin/ctap/bugs/snails.htm Accessed 03/10/01.

Immink, A., Dutta, G., Kumar, B. and Little, D. 2001. Fry supply across

West Bengal. Aquaculture News. Inst. of Aquaculture, University of

Stirling, Stirling., 27:13 -14.

Jhingran, V. G. (1991). Sewage-fed fisheries. In Fish and Fisheries of

India, 3rd Edition. Chapter 15. pp 490 - 497.

Jokai, Z., Hegoczki, J. and Fodor, P. 1998. Stability and optimisation of

extraction of four arsenic species. Microchem. Jour., 59 (1): 117-124.



Kundu, N. 1994. Planning the Metropolis, a Public Policy Perspective.

Minerva Associates Ltd. Calcutta, India. 54 pp.

Medschool. 1999. Aluminium hydroxide and magnesium trisilicate.

Medschool.(http://medschool.com/futuretense_cs/…s/patch_f/html/chapt

er/mono/hf003610.htm) Accessed 16/09/01. 1 pp.

Mukhopadhyay, S. K. (1999). Carp culture in waste water. Fishing

Chimes. 19 (7): 9 – 11.

Nandeesha, M.C. (2002). Sewage Fed Aquaculture Systems of Kolkata-A

Century-old Innovation of Farmers. Aquaculture Asia. VII (2): 28-32.

Ranadhir, M., Gupta, S.D. and Reddy, P.V.G.K. 1990. Economics of carp

seed production. In: P. Keshavanath & K.V. Radhakrishnan (edts),

Carp Seed Production technology: proceedings of the workshop on carp

seed production technology 2-4 September, 1998. Asian Fish. Soc.,

Mangalore, India. 82-88 pp.

Sinclair, W. 2001. Malathion Medical Research. University of Florida,

Florida. (http://chemtox.com/malathion/research/index.htm). Accessed

16/09/01. 1-17 pp.

Tripathi, S.D. & Khan, H.A. 1990. Carp seed production technology – a

review. In: P. Keshavanath & K.V. Radhakrishnan (edts), Carp Seed

Production technology: proceedings of the workshop on carp seed

production technology 2-4 September, 1998. Asian Fish. Soc.,

Mangalore, India. 53-56 pp.



A Famous Oil Painting on Fishery

Sewagefed aquaculture system

Documents

Transcript of Sewagefed aquaculture system