Impacts of Prawn Culture

7/29/2019 Impacts of Prawn Culture

1/38

4. Prawn Culture Impacts

4.1 Prawn culture impacts to environment

The environmental problems which may be associated with shrimp

farming are well documented (Macintosh and Phillips 1992; Landesmann 1994;

Pullin et al. 1993; Phillips 1995a and 1995b) and include mangrove deforestation;

reduction of habitat; reductions in shoreline protection; increased coastal erosion;

coastal water pollution; nutrient enrichment; depletion of wild prawn and fish

larvae stocks; land subsidence; salinisation of soils, agricultural land and ground

water, activation of acid sulphate soils; loss of agricultural lands; introduction of

exotic species and the discharge of undesirable chemicals. Whilst these

problems have been identified, quantification of them is difficult.

4.1.1 Deforestation mangrove

The term mangrove refers to salt-tolerant species of tree or shrub which

grow on sheltered shores and in estuaries in the tropics and some sub-tropical

regions. There are about 60 species which occur exclusively in this habitat, and

many non-exclusive species. Mangroves are outstandingly adapted to growing in

seawater, which they desalinate by an ultrafiltration process. Mangrove roots

typically grow in anaerobic sediment and receive oxygen through aerating tissue

which communicates to the air through small pores (lenticels) on the aerial roots

and trunks. Mangroves may occur as narrow fringes on steeper shores and river

banks, or as Mangrove forests in optimum conditions are one of the most

14


2/38

productive ecosystems; for example a net primary productivity of 23.3

tonnes/ha/year and litter productivity of 10 tonnes/ha/year was measured for a

15-year-old stand ofRhizophora at Matang, Malaysia. The litter (such as fallen

mangrove leaves) is broken down by bacteria, fungi and herbivores, and the

resulting detritus supports food webs including large populations of invertebrates

and fish. The calm waters in the forests are ideal breeding and nursery grounds

for young fish and shrimps, while the aerial roots, lower trunks and mud surface

usually support a varied fauna of oysters, snails, barnacles, crabs and other

invertebrates. The upper part of the mangrove trees is an essentially terrestrial

environment with a fauna of birds, mammals and insects. Mangroves are

affected by the freshwater and nutrient supply which they receive from their

catchment area, and on the other hand have a strong influence on the adjoining

coastal waters and associated ecosystems such as coral reefs, seagrass beds

and tidal marshes. For example, they trap and stabilize sediment which might

otherwise limit the growth of corals.

Most mangrove forests in Malaysia are found along the meandering

coastline of Sabah (350,000 hectares) followed by those in Sarawak (175,000

hectares) and in Peninsular Malaysia (105,000 hectares). Total area of

mangroves in Malaysia is only about 3% (630,000 hectares) of the total land area

of Malaysia. Conversion to shrimp/fish ponds, in addition to settlements,

agriculture, salt beds, overexploitation and other factors, have led to high rates of

mangrove loss ranging from 25% in Malaysia. Most of the shrimp ponds opened

during the 1980's and early 1990's involved the clearcutting of mangroves. Local

15


3/38

fisherfolk are severely concerned about the increased loss of mangroves as this

has led to decrease in wild stocks and extinction of several commercial fish

species in some places. The Penang Inshore Fishermen Welfare Association

states that its survey revealed that 34 species of fish have become extinct and

another 50 or more are becoming rare in the waters off Penang. Shrimp

aquaculture is considered by many scientific experts to be the largest

contributing factor to present day loss of mangrove ecosystems. The alarming

rate of expansion of shrimp farming along mangrove coastlines throughout the

tropics and subtropics demands immediate attention.

The destruction of coastal mangroves has also brought about coastal

erosion. The coastal villages are susceptible to critical erosion, battered by

strong waves and storms. Their life and property is at stake as the raging sea is

slowly swallowing the coast. Mangrove ecosystems protect shorelines from

erosion, storms, and, as we learned in 2004, from tsunami damage, through their

ability to reduce wave action and wind velocities in coastal areas. Mangrove

ecosystems include the mangrove forest itself; its associated faunal community,

and adjacent and hydrologically linked wetlands. The landward portion of the

ecosystem includes salt flats or salinas, and freshwater streams and wetlands

which ultimately drain to the sea via surface and underground waterways. The

seaward edge of the mangrove ecosystem is the outer edge of the influence of

water flows coming from drainage through mangrove forests and may extend

several miles offshore, affecting associated ecosystems, such as seagrass beds

and coral reefs. International trade is also posing significant threats to mangrove

16


4/38

forests, another critical coastal ecosystem that is intimately connected to coral

reefs. Mangrove forests serve as important nurseries for many reef species.

They help to maintain coastal water quality by reducing the run-off of sediments,

pollutants and excess nutrients from the land. Nutrients and energy flow between

these habitats as species move between them. Some environmental and

economic benefits of mangroves

Help protect coasts and river banks from erosion

Help protect coastal dwellers from storms and storm surges

Help reduce peaks of nutrient and sediment discharges from coastal rivers

Help trap sediment and build new land

Help reduce atmospheric CO2 levels by fixing and storing carbon

Produce leaf litter and other detritus that support coastal food chains

Provide nursery and feeding ground for fauna, including commercially

valuable fish, shrimp, crab, gastropods and bivalve species

Provide timber and fuel wood for coastal dwellers

Provide other products like honey and medicinal drugs

Enhance biodiversity

Provide aesthetic and recreational values

Provide scientific, educational and cultural values

Mangroves are not the best site for shrimp culture, as they have

potentially acidic soil. Shrimp ponds may have problems with low pH, which is

bad for the health and survival of shrimp. Also, when mangroves are converted

17


5/38

into aquaculture ponds, valuable environmental benefits are lost. In general, it is

better to set up aquaculture ponds on higher land behind mangroves. The putting

up of new aquaculture ponds within mangrove areas should be discouraged.

However, brackish water shrimp ponds have already been built in many areas

due to the mangrove located near the sea shore to accommodate prawn culturist

with sea water stock used in prawn and shrimp culture.

Figure 9: Mangrove area in Malaysia.

18


6/38

Table 5: Total landing of various fisheries products on the west and east

coasts of peninsular Malaysia.

4.1.2 Impacts of Ponds Discharge to Soils and Ecology

Role of nutrients and organic matter Studies with- intensive shrimp

farming suggest that nutrients and organic matter in shrimp pond wastes have

potential for the following impacts:

Reduce dissolved oxygen in receiving waters, due to discharge of waste

water low In dissolved oxygen and breakdown of dissolved- solved and

participate organic matter and other waste materials (BOD and COD);

Hyper-nutrification and eutrophication of receiving waters, resulting in

increased primary productivity (with potential risks of phytoplankton

blooms).

Alteration of biological community structure and secondary productivity

Increased sedimentation due to organic matter leading to changes in

productivity and benthic community structure, plus possible situation.

19


7/38

Such impacts depend on the quantum of waste water outflow and the

capacity of the environment to assimilate the waste materials. It is, therefore,

desirable to match loads with the capacity of the environment to accept the waste

materials.

Prevention Steps to Avoid Impacts of Ponds Discharges

Problems encountered during aquaculture experiments in ponds

constructed on acid sulfate mangrove soils are described. Entry into the ponds of

acid water with a high iron content and activity of iron oxidizing bacteria were

identified as major contributors to the problems. Design features and

management practices which minimize entry of acid water and reduce the

harmful effects of acidity and iron are presented. These include reducing the size

of the dikes, using a pumped water supply and employing mechanical circulation

and mixing of pond water.

Efforts to develop pond culture at the Brackish water Aquaculture

Research Centre, Gelang Patah, Johor Bahru, Malaysia have encountered

problems. Mortality of the species cultured is high and growth is frequently slow

due to a number of complex conditions associated with acid sulphate soils. The

major problem is entry of acidic water containing high levels of dissolved iron into

the ponds. There are three principal ways by which the acidic water enters a

pond. The most important is runoff of rainwater which becomes acidic after

reacting with oxidized pyrite in the soil (Potter, 1976). Another problem is entry of

acidic dike pore water during draining and filling the ponds with tidal water. There

20


8/38

is also some addition by seepage through the dikes. The pond bottom is not a

continuing source of acid once it is leached well and kept submerged.

Use of chemicals

Chemicals should be avoided in shrimp culture ponds for prevention or

treatment of disease, as feed additives, disinfectants for removal of other fish or

for treatment of soil or water. However, chemicals may be required in hatcheries.

Entry of such chemicals into the natural waters from the hatcheries should be

carefully monitored and steps should be taken to remove such materials from the

waste waters.

Use of fertilizers

Both organic and inorganic fertilizers are used widely in semi-intensive

culture systems for promoting the growth of fish food organisms. particularly for

the early postlarval stages. This may contribute to the nutrient load in receiving

water. Therefore, as far as possible only organic manure/fertilizers and other

plant products should be used for such purposes

Use of piscicides

Similarly, piscicides and mollusclcides are widely used for removing

predators and competitors from shrimp ponds. It would be advisable for

aquaculturists to use only the biodegradable organic plant extracts for this

21


9/38

purpose as they are less harmful than the chemical agents. Use of chemical

piselcides in culture systems should be avoided.

Use of chemotherapeutants

Some of the chemotherapeutants such as formalin and malachite green

which are commonly- use as disinfectants are known to be toxic and many affect

adversely the pond ecosystem. The external waters, etc. and hence their usage

in culture system should be avoided.

Use of antibiotics/drugs

A number of antibiotics used in shrimp culture for preventing outbreak of

disease are harmful and may result in development of shrimp pathogens

resistant to such drugs and the transfer of this pathogen's into human beings

might result in development of resistance in human pathogens. The use of

antibiotics/drugs in culture system, therefore, should be avoided.

Outbreak of disease in shrimp culture system is related to the

environmental factors such as deterioration of water quality, sedimentation and

self-pollution. The production losses are also linked to the acid sulphate soil

particularly in the areas. Another consequence of industrial shrimp farming is the

use of antibiotics, pesticides, fungicides, parasiticides, and algicides. To guard

against diseases farmers also use a large amount of antibiotics during production

as well as toxic chemicals between harvests to sterilize the ponds. The result is

that human consumers of tropical shrimps produced in this way are eating food

22


10/38

containing high levels of antibiotics. Many of the substances used in this activity

are prohibited in some countries due to their carcinogenic effects. Regarding

antibiotics, some of the ones that are used in shrimp farming are the ones used

in humans, which might decrease the effectiveness of antibiotics against

diseases. In Malaysia, there are regulations limiting the amount of chemicals

used.

Use of soil with least acidity

The intensity of acidification in any area is patchy and in general the

deeper the soil is excavated the more acid the soil. Also, the content of iron,

sulphur and aluminium increases with depth. Frequently, the top 2030 cm of soil

is good. An example of this can be seen in a study of soil distribution in the delta

of the Sarawak River (Andriesse et al., 1972). In the Sarawak River Delta there is

only a small area of Pendam series soil which has acid and potentially acid

sulphate soil (pH 3.9) in the surface 15 cm. Most of the area is composed of

Rajang series soil which is characterized by top soil with a near to neutral pH and

subsoil (6075 cm depth) which is potentially acidic. If brackish water ponds were

built in the Pendam series area they would experience problems no matter how

they were constructed. In the Rajang series area severe problems would be

encountered if it was decided to excavate to expose the potentially acid sulphate

soil which occurs at depth. It is preferable for ponds to be constructed with only

minimal excavation. The land should be levelled and only enough of the neutral

top soil to build the dikes should be used.

23


11/38

At this point it should be remembered that pH is a logarithmic function.

That is, pH 4 is ten times more acidic than pH 5, and pH 3 is ten times more

acidic than pH 4 and 100 times more acidic than pH 5. Thus tremendous

leverage is obtained when soil with a higher pH is used for the dikes. It may not

be necessary to have the dike soils near to neutrality to obtain significant benefit.

As pointed out in this report many of the problems in shrimp culture involve iron.

Iron is not soluble at pH 4 and above. There are few places where the surface

layer is lower than pH 4.

The dikes should be small as possible

In most places it is necessary to excavate in order to locate pond bottoms

at a level where tidal fluctuation can be used to fill the ponds with water. That

was the case at the Gelang Patah Research Centre. Natural ground elevation at

the site rose to 1.8 m above mean sea level (MSL). Excavation was undertaken

to situate the pond bottoms at 30 and 45 cm above MSL. As the excavated soil

must be disposed of, in this case it was incorporated into dikes which resulted as

massive. The dikes around one 0.25 ha pond adjacent to the main dike were

measured as an example. The height of the dikes varied from 1.1 to 2.8 m above

the water line. Distance from the mid-point of the dike to the water varied from

4.5 to 16 m. The surface area of the dike amounted to about 36 percent of the

total area and 55 percent of the pond water surface. The great soil surface area

ensures that a large amount of runoff will enter the pond when it rains, and the

24


12/38

fact that it was excavated from depth ensures that the runoff will be very acidic,

with pH under 3.5.

If the pond had been built by levelling the land and using only top soil to

construct a small dike it is assumed that the height of the dike would be 0.5 m

above water and the average distance from the mid-point of the dike to the water

would be only 2.2 m. This would reduce the surface area of the dikes to only 18

percent of the total area and 15 percent of the water area. Rainwater runoff

would be drastically reduced, as in addition to the reduction in the surface area of

the dike, the volume of water in the pond had been increased. In the existing

pond a 10 cm rain would result in 137 m3 of rainwater runoff into 2 400 m3 of

pond water. In a non-excavated pond only 60.5 m3 of rainwater would run off into

3 312 m3 of pond water. The amount of run-off would be reduced from 5.5 to 1.8

percent of the volume of water in the pond. Even if the runoff was acidic the

effect on the pond would be drastically reduced, but as seen earlier the top soil

would probably be less acidic.

An experiment was carried out to assess the effect of adding acid water to

the ponds. Thoroughly dried dike soil was pulverized and different amounts were

added to two beakers of tap water to make them acidic. One solution was made

with a pH of 3.44 and another with pH 2.88. Each of these solutions was added

sequentially to brackish water from the ponds which had a pH of 6.9. The

resulting pH values were then plotted as a percentage of total water volume. This

showed that adding 5.5% of pH 2.88 water reduces the pH of the pond water

25


13/38

19.5% and adding the same amount of pH 3.44 solution reduces pH by 9%.

Adding only 1.8% of the pond volume at the same pH would reduce the pond

water pH by 8.8 and 5.2% respectively. Thus by reducing the amount of runoff

from 5.5 to 1.8 percent of the pond volume the reduction of pond water pH would

decrease from 19.5 to 8.8%.

This also points to the importance of reducing pH of the runoff water. A

reduction of only 0.56 pH units would exert about the same effect as reducing the

amount of runoff by 67 percent. The change in pH would be reduced from 19.5 to

9 percent.

Increasing the water volume in a pond

The volume of water in a pond relative to the surface area of dike subject

to runoff can be increased in two ways; increasing depth and increasing pond

size. Both of these options have serious limitations if a tidal water supply is

planned. The primary problem revolves around the elevation of the pond bottom.

In order to ensure an adequate supply of tidal water the land must be excavated

to construct the pond bottom at the proper elevation in relation to the tide. This

usually requires some compromise. If the bottom is situated low enough to

maintain a high level of water in the pond it is usually not possible to exchange

water on neap tides. If water can be exchanged only on spring tides,

management is restricted. If the bottom is too low, it is not possible to drain the

ponds for harvesting and certain pond preparation procedures. Also, as already

pointed out, excavation into the deeper zones exposes soils with a lower pH, and

26


14/38

the soil removed must be incorporated into dikes or removed. Removal is very

expensive. If the land has to be excavated, the cost of building very large ponds

becomes prohibitive because the earth from the centre of the pond must be

moved a long distance. In most locations ponds larger than 1 ha probably would

not be economic if they have to be excavated.

Eliminating fluctuations in water level

It would seem that if water in the pond is of poor quality it should be

changed. This has some bad effects. Draining and refilling a pond during water

exchange causes movement of water in and out of the dike. The pH of interstitial

dike water can be as low as 3 and iron content ranges from 100 to 200 ppm. Iron

content of rainwater runoff is only of the order of 2025 ppm. So even if less

water is involved in the exchange of pore water its higher iron content increases

its relative importance (see Chapter 2 of this report). This is an important factor

even during dry periods and may account for a great deal of the iron-related

problems. The only way to prevent this is to maintain a constant level of water in

the pond.

Increasing pH and decreasing iron of run-in water

Several methods have been suggested for reducing the amount of acid

and iron entering the pond. One of the most important is to establish vegetation

on the dike and at the water's edge. Vegetation on a dike stabilizes the surface

and prevents erosion so that the soil has time to weather before it is washed

27


15/38

away. On acid sulphate dikes with high clay content the surface cracks with only

a small amount of drying. During the next rain many of the small dry particles are

washed into the pond. As the soil particles are fully oxidized they contribute a

maximum amount of acidity and iron to the pond water. Perhaps an equally

important factor is that the fairly large pieces of soil form a porous zone right at

the water's edge. This acts as a sink for small floating organic particles which are

washed up to the shore by wind. Often the organic material which originates on

the pond bottom (benthic bluegreen algae) is coated with iron. Also films of

oxidized iron which form on the pond surface are blown on the pond edge by

wind. Consequently, high levels of iron and organic matter accumulate in the soft

intertidal zone. Due to the high level of organic matter the soil becomes

anaerobic and in the absence of oxygen the iron assumes the soluble Fe++ state.

During drawdown for tidal water exchange the pore water high in iron seeps back

into the pond and the cycle starts again. Planting grasses such as buffalo grass

(Paspalum conjugatum) and digit grass (Digitaria decumbens) prevents this,

because the grasses trap the soil particles before they enter the water.

Furthermore, these grasses take up iron from the soil thus removing them from

the cycle (Cook et al., 1984).

The main point brought out in the preceding sections is that in areas with

acid sulphate, or potentially acid sulphate soil, ponds should be built with a

minimum of excavation. Such ponds would naturally have a high bottom

elevation and it is unlikely that tidal water exchange would be effective. Water

would have to be pumped into such ponds. Pumps are frequently used to fill

28


16/38

ponds in Thailand and South America, but many people still question the use of

pumps as an economically viable alternative to free tidal water.

A case study was made by Gedney et al., (1983) to compare cost factors

involved between constructing and operating tidal water exchange aquaculture

farm systems and a pumped water system. A comparative assessment was

made of three different systems:

A tidal farm excavated to a depth of +0.3 m above mean sea level

(MSL) from a natural ground elevation which varied from +0.9 m to

+1.2 m.

A tidal pond system excavated to a depth of +0.3 m above MSL

from natural ground elevation which varied from +1.5 to 1.8 m.

A pumped water pond system at a natural ground elevation varying

from +1.8 to +2.7 m above MSL.

The study showed that a pump system offers advantages in terms of lower

costs. A summary of construction and operating costs for the different pond

system is given in Table 1. As the study was done at the Brackish Water

Aquaculture Research Centre, costs and benefits reflect Malaysian conditions.

Acidity of the pond bottom soil is not really a problem. After a short period

of flushing and submergence the top layer becomes neutralized by carbonate in

seawater and deeper layers become anaerobic. In either case the pH rises. As

pointed out earlier iron is harmful. It accumulates in the pond, and once in the

29


17/38

pond it acts independently of acidity. It recycles between a reduced state in the

pond sediments and an oxidized state depending on bacterial action and the

quantity of oxygen in the soil. Bacteria oxidize the iron and the bottom flora

becomes coated with oxidized iron. During the day the benthic algae, coated with

oxidized iron, float to the surface where wind action carries them to the side of

the pond. This material accumulates at the pond edge and becomes incorporated

in the loose unconsolidated sediments carried into the pond from the dike by

rainwater. Gradually as one layer forms on top of another the bottom layers

become anaerobic and the iron reverts to the soluble ionic state. Then it is

leached back into the pond in dike pore water during drawdown for tidal

exchange.

It is advisable to remove as much iron as possible from the pond. Addition

of lime would just bind more iron. One way to remove the iron is to make the iron

change to a soluble form and then flush it from the pond. The iron is soluble

below pH 4. A good way to remove iron would be to fill the pond with acid to

dissolve the iron. This can be accomplished by drying the pond thoroughly and

tilling it to aerate and dry the soil at deeper levels.

After the soil is completely dry, just enough water is let in to cover the

bottom. This water will become very acidic and the iron will be dissolved. The

water is then drained from the pond and the flushing process repeated until the

water pH rises above 4. If too much water is let in during the initial filling, pH will

rise above 4 and most of the iron will precipitate back out of solution.

30


18/38

Furthermore, moist soil should not be flushed. The pond bottom must be

thoroughly dried to oxidize the iron. After the pH of the water no longer drops

below 4, flushing should be continued with the water level as high as conditions

permit. The entire system inside the perimeter dike should be flooded if possible.

This will leach acidity from the dikes.

Planting grass, especially at the water edge is recommended. Grass at the

water's edge prevents entry of small oxidized soil particles which are washed into

the pond by rainwater and contribute iron to the pond. Prevention of the

accumulation of these loose soil particles at the water's edge reduces the amount

of soil pore water which enters the pond during drawdown. The plants also take

iron up from the soil, and its removal from the recycling process is beneficial. It

must be mentioned that maintaining water level at a constant depth would help

reduce the recycling of iron.

4.2 Prawn Culture Impacts to Social

Although prawn farming is still a small industry in Malaysia, the social

impacts have already become evident. The mangrove ecosystems provide direct

food resources and habitat for many forms of fish and wildlife, including many

directly harvested by subsistence-based villagers and fisherfolk living in or

adjacent to the mangrove ecosystem, and commercial harvests of fishery

resources, including wild-caught shrimp, crabs and fish. Among the most

worrying are the loss of livelihood and income of small coastal fisherfolk due to

mangrove loss and fish decline, negative changes in agricultural practices, and

31


19/38

human rights violations. The most controversial shrimp project in Malaysia is in

Kerpan (Kedah). Samak Aquaculture was approved as a joint venture company

in 1993 where villagers where ordered by government to sell their paddy field to

be converted to shrimp ponds.

Therefore, access to the sea front and other common resources to the

coastal communities by the aquaculture units should be ensured. The interests of

the communities and organisations in the area should be safeguarded.

Large-scale shrimp aquaculture may bring an excessive demand on land

resources, resulting in multi-user conflicts. Construction of shrimp ponds may

make inroads into agricultural land. States must undertake surveys to identify

lands which are fit for different purposes. They should discourage conversion of

agriculture land for aquaculture. Construction of shrimp ponds on marginal land

not fit for cultivation alone should he permitted.

4.3 Prawn Culture Impacts to Economy due to Viral Diseases

Prawn culture had been an alternative economy source and income

generation of villagers in Malaysia. In the past years, the aquaculturists mostly

are villagers with lack of knowledge in prawn culture relating to the lack of

scientific research spread out to the aquaculturists. During this time, million of

ringgit loss due to the outbreak of disease in shrimp culture system which is

related to the environmental factors such as deterioration of water quality,

32


20/38

sedimentation and self-pollution. The production losses are also linked to the

acid sulphate soil particularly in the areas. However, in recent years, the

production of cultured shrimp has markedly decreased as a result of serious viral

disease outbreaks. Especially, the increased severity of widespread White Spot

Syndrome Virus (WSSV) infection is the most serious threat to stable

aquacultural production. In the case of Malaysia, outbreak of this disease was

almost the same as Thailand situation that was WSSV disease occurring as

serious problem from 1996. A lot of farms have given up shrimp culture due to

heavy loss incurred by WSSV until 1997. Field research was performed through

1998 and 1999 on the occurrences of WSSV at farms in Malaysia. Dark-field

microscope observation and Japanese PCR methods for PRDV detection were

used for this research, because both methods were confirmed to use for

detection of Malaysian strain of WSSV.

From this research, WSSV outbreaks were found in Penang, Kedah and

Sarawak State, and information of the occurrence of viral disease was obtained.

Almost all prawns in the ponds were dead by this disease. These dead prawns

were showing many clear White spots on their carapace. Pathogenic viruses

were confirmed by PCR from the samples WSSV. In this etiological study, as for

the infection routes, it could be supposed two ways. One was that the prawn fry

had been infected with this virus, and another was from supplied seawater

containing the virus particles. As one of the preventive countermeasures against

viral diseases, inactivation methods for WSSV were studied. This viral

inactivation was tested with formalin and halogenous disinfectants and sodium

33


21/38

hypochlorite. These chemicals were mixed with the virus and injected to the

healthy prawns. As a result of these experiments, no mortality was shown using

0.25% effective chlorides in sodium hypochlorite and 0.5 ppm formalin. From

these results, sodium hypochlorite of halogenouse disinfectants showed the

effective inactivation even under lower concentration. It was suggested that these

disinfectants were extremely useful for the WSSV inactivation.

Figure 10: Prawn with White Spot Syndrome Virus (WSSV)

5. Prawn Culture Site Selection and Legislation

5.1 Site selection and culture management

A vast majority of problems affecting the shrimp culturists as well as the

environment could be avoided by better site selection and improved culture

management. Site selection process should include proper environmental impact

assessment. The existing criteria for site selection also need to be reviewed and

consideration should be given to long-term capacity of the area to sustain

aquaculture development.

34


22/38

5.2 Master plan for development

Detailed master plans need for development of prawn culture through

macro and micro-level surveys of the potential areas and conation of coastal

area delineating the land suitable and unsuitable for aquaculture using the

Remote Sensing data, ground truth verification, Geographical Information

System. (GIS) and socioeconomic aspects should be considered.

5.3 Environment Monitoring and Management Plans (EMMPS)

The shrimp culture units with a net water area of 40 hectares or more shall

incorporate an Environment Monitoring Plan and Environment Management plan

covering the areas mentioned below:

Impact on the water sources in the vicinity

Impact on the waste water treatment.

Impact on drinking water sources.

Impact on agricultural activity

Impact on soil and soil salinisation

Green belt development (as per specifications of the State Pollution

Control Board)

All farms of 10 hectares and more but less than 40 hectares shall

furnish detailed information on the aforesaid aspects.

35


23/38

5.4 Environment Impact Assessment

An Environmental Impact Assessment (EIA) should be made even at the

planning stage by all the aquaculture units above 40 hectares size. For 10

hectares and above a statement will be required to be given in the detailed plans.

The State Pollution Control Boards should ensure that such a EIA has been

carried out by the aquaculture units seeking No Objection Certificate from them,

before giving clearances for such projects.

5.5 Feed quality and its management

The quality of feed plays an important role in waste output in shrimp

culture, and there is scope to Improve pond environment by good feed

management. Nutrients and organic loads are higher in ponds where shrimps are

fed within trash fish and fresh diets than where palletized moist or dry feeds are

used. Fresh diets, infrequent feeding and high stocking densities increase

nitrogen loads in the waste water from the shrimp farms. A considerable amount

of detritus and wastes often accumulated- on the pond bottom, in areas where

water circulation is slow, leading to increased BOD and release of harmful gases,

which could cause stress on bottom living shrimps. On the contrary, regular

feeding with pelletised diets is known to maximize the growth of shrimps and

minimize the nutrient enrichment of the waste water.

The feed waste plays an important role in the total waste loadings In the

environment. This is because; feed settles directly on the pond bottom and the

36


24/38

feed wastage can have a significant effect on sediment quality and ultimately the

health of the shrimp which normally live at the bottom.

Hence the use of wet diets such as fresh fish and invertebrates has to be

reduced and preferably avoided in shrimp aquaculture systems. Feed

Conversion Ratio (FCR) should also be optimised. Monitoring of feed input is

required to keep feed wastage to the minimum. Similarly, careful monitoring of

standing stock in the ponds will also help to ensure that correct feeding levels are

observed.

5.6 Rules and regulations governing Aquaculture

The law governing fisheries in Malaysia is contained in the Fisheries Act

1985. Under this Act, the Fisheries (Marine Culture System) Regulations 1990

have been made and gazetted in 1990. Culture systems covered under these

Regulations include rack and pole culture, raft culture, cage and pen culture, and

on-bottom culture systems.

Besides these Regulations, the Government has also introduced various

incentives for the development of aquaculture in the country (Hoo, 1985). These

incentives include pioneer status, investment tax credit and export incentives.

5.7 Shrimp aquaculture in international environmental treaties

The ecological and social impacts of shrimp aquaculture have been

brought to the attention of two international environmental treaties that have been

37


25/38

developing policies and programs for the sustainable management of coastal and

other ecosystems. These are the RAMSAR Convention on Wetlands and the

Convention on Biological Diversity (CBD).

The Forest Peoples Programme, an ISA Net (Industrial Shrimp Action

Network) member organisation, made an intervention highlighting the impacts of

shrimp farming on coastal and marine ecosystem and local communities at the

Conference of the Parties 4 (COP4) of the CBD in May 1998 in Slovakia.

The following year several ISA Net members participated in the 7th

Conference of the Parties of RAMSAR and at a workshop on Indigenous Peoples

and Local Communities' Participation in Wetland Management during the 13th

meeting of the Global Biodiversity Forum (GBF) which preceded the RAMSAR

meeting (San Jos, Costa Rica, 7-18 May, 1999). The presentations made by

four representatives of local communities were well received at the GBF and ISA

Net's recommendations were discussed at the RAMSAR Conference. As a result,

a paragraph was added to one of the final resolutions (Resolution VII.21,

Enhancing the conservation and wise use of intertidal wetlands), calling for the

suspension of the promotion, creation of new facilities, and expansion of

unsustainable aquaculture activities harmful to coastal wetlands until measures

aimed at establishing a sustainable system of aquaculture that is in harmony with

the environment and local communities are identified.

38


26/38

ISA Net members also participated in discussions and amendments of the

Guidelines for establishing and strengthening local communities' and indigenous

peoples' participation in the management of wetlands, which were eventually

adopted as Resolution VII.21 and VII.8 of the COP.

Getting useful language into international conventions, however, can only

be considered an achievement if they become effective tools to be used by local

organisations in their efforts to protect their environment and livelihoods. NGOs

and CBOs in Ecuador and Honduras have so far tried to use the paragraph on

aquaculture of RAMSAR Resolution VII.21 in order to stop further expansion of

shrimp farming in ecologically sensitive coastal ecosystems. So far, it seems that

the RAMSAR language might have been helpful in supporting the effort of

Ecuadorian NGOs trying to stop the introduction of new policies that would have

included the privatization of parts of the coastline for the benefit of shrimp

farmers. On the other hand, it does not seem to have been particularly useful in

the Gulf of Fonseca, Honduras, despite the fact that part of the Gulf is a

RAMSAR site. Effective follow-up needs to be organised to make sure that

language developed in RAMSAR does not remain empty words.

Meanwhile, a programme under the CBD, namely the Jakarta Mandate on

Coastal and Marine Biodiversity, has developed a 3-year work plan for the

conservation and sustainable use of marine and coastal biological diversity. This

includes a section (programme element 4) on mariculture, whose main

39


27/38

operational objective is to assess the consequences of mariculture for marine

and coastal biological diversity and promote techniques that minimise adverse

impact.

5.8 List of Relevant Institutions

Training of aquaculture extension workers within the Department of

Fisheries Malaysia is conducted from time to time by the Fisheries Research

Institute (of the Department of Fisheries, Ministry of Agriculture Malaysia) at its

headquarters in Penang, and also at its branches, i.e. at the National Prawn Fry

Production & Research Centre, Kampung Pulau Sayak, Kedah particularly in all

fields of coastal aquaculture; at the Brackish water Aquaculture Research

Centre, Gelang Patah, Johore in certain aspects of brackish water pond

management; and at the Freshwater Fish Research Centre, Batu Berendam,

Malacca in special courses on freshwater fish breeding and culture. The training

courses are organized by the Extension and Training Division of the Department

of Fisheries Malaysia, and the courses are usually conducted jointly by staff from

this Division as well as from the Fisheries Research Institute and its branches.

Certain courses for aquaculture extension workers are also organized and

conducted by the Extension and Training Division at the Fisheries Training

Institute, Batu Maung, Penang.

Many of these endeavours have proven non-sustainable with the result

that large areas of ponds have been left idle and disused, some have been

40


28/38

abandoned and new sites are being developed in an effort to maintain

production. This presents a major challenge for both coastal resource managers

and pond owners who will have to address the question of what to do with

disused ponds. There are three basic options. The first is to rehabilitate the pond

sites so that they can be put back into shrimp production. The second is to

rehabilitate the pond sites so that they can be put to some alternative,

sustainable use such as salt production. The third option is to restore the

environmental conditions within the pond site and the surrounding area, and to

re-establish a productive mangrove ecosystem. Each of these options is heavily

influenced by the causes of failure of the pond operations and the conditions

which remain in the pond after disuse. This paper briefly explores the issues that

must be faced if rehabilitation and restoration are to be successful.

Figure 11: Suggested sequence for improving the separate farming

system

41


29/38

Figure 12: LKIM aquaculture programs in Peninsular Malaysia

6. Recommendations to Prawn culturist

6.1 Small-scale improved extensive and semi-intensive shrimp

culture

Increasing the stocking density (up to, but not more than, 10 per meter)

and the survival rate ofP. monodon in the pond can improve the contribution of

shrimp farming to the livelihood of small-scale farmers in coastal areas. This can

be achieved through modest intensification, together with better pond design,

good quality seed and improved farm management practices. A range of options

for improvement require different levels of investment. It is necessary to show

farmers a sequence of steps they could take to increase their income. These

42


30/38

steps depend on the condition of the farm, individual financial circumstances and

experience.

The three main requirements

1. A good pond

2. Strong, high quality and disease-free seed

3. Good nursery care during the first 20-25 days of stocking

Some general suggestions on farm layout

Remember that coastal mangrove systems are highly dynamic and their

characteristics often change. What is seen now may not be the same in 10-20

years time. Try to anticipate future changes and make plans with these in mind.

This will help avoid future problems that might be costly to fix.

Try to keep a 20-30 m wide belt of mangroves along the waterfront to

reduce erosion and provide a nursery for wild aquatic species.

Try to maximize the benefit of mangroves by arranging the location to

allow incoming or outgoing water to pass through the trees.

Pond design

A small pond with a water area of about 2000 or 2500 sq m is better than

a much larger pond. Big ponds are more difficult to manage. Start with one pond,

and then add another as capital becomes available. This will help reduce the risk

of losing shrimp through disease. No more than three ponds of this design should

be built. See suggested sequence for the two main farming systems in the

illustrations.

43


31/38

Some useful tips on pond preparation

Use a sedimentation pond to improve water quality if the intake water

has low transparency, is polluted or otherwise of low quality. Generally the water

surface area of the sedimentation pond should be at least equal to the water

surface area of grow out ponds. The sedimentation pond can be stocked with P.

monodon at a density of 1-3 per sq m or it can be used for wild shrimp culture.

Cannot dump the excavated material into the river or in mangrove

areas. Use it to build an area above the tidal limit, which can be used for

terrestrial crops or livestock production. Diversification can help reduce the risk to

the household and provide a more stable income.

Make sure the average pond water depth is 1 m.

Use a cement water gate that is at least 1 m wide. If necessary, use

plastic sheets or fibro-cement roofing material to prevent water leakage through

crab burrows along the sides of the water gate (refer to the diagram on the right).

Outer levees (or dikes) should be at least 4-6 m wide to reduce leakage

(10 m is preferable). The levee (dike) around the pond should be at least

0.5 m higher than the highest tide to reduce the risk of shrimp being washed out

of the pond by unusually high tides or storm surges.

After constructing or after cleaning the pond, open the watergate and

allow the tide to free flush the pond for at least a week. Put a net at the water

gate to prevent entry of predators (e.g., fish). Avoid using chemicals to kill

predators. If absolutely necessary, use only sparingly. Use Derris root or tea

44


32/38

seed powder, both natural products, if pesticides are needed. In some areas with

acidic soils, it may be necessary to apply lime.

Prepare a nursery area at least 1 week prior to stocking, using fine net

(equal or less than 1mm mesh size) to cordon off the nursery from the rest of the

pond. The size of the nursery area should be calculated for a stocking density of

about 35-50 per sq m.

Viral and bacterial diseases are more difficult to manage. Using disease-

free seed is the first step that farmers can take to reduce the risk of diseases.

However, viral and bacterial pathogens are probably present in most wild shrimp

populations, so that there is always a risk that disease can be transferred from

wild to cultured shrimps that were initially healthy. Crabs can also be vectors of

some shrimp diseases. Hence, it would be best to exclude wild shrimp and crabs

from the grow-out pond. Shrimps, like all animals including humans, are more

likely to contract a disease if they are weak or stressed. Good pond and water

quality management practices that keep shrimps strong and healthy will also help

reduce the risk of death from viral and bacterial disease.

The Penang Inshore Fishermen Welfare Association (PIFWA) has recently

held a workshop on the importance of mangroves. Fisherfolk were aimed to

highlight what they suppose to know about prawn culture and mangrove forest

which is an inherent part of their livelihood since it is closely related to fish catch.

Without mangroves there will be no fish in the sea since mangrove play a vital

role as intermediaries between marine and terrestrial ecosystems.

45


33/38

Figure 13: Suitable Location of Prawn ponds.

Figure 14: Agriculture land is unsuitable location for prawn ponds.

Figure 15: Site Selection of prawn ponds near the sea water source.

46


34/38

7. Disuse and Abandonment of Prawn Farm Ponds

7.1 Causes of Disuse and Abandonment of Shrimp Ponds

Disease has been widely cited as a cause of production failure, and the

shrimp industry has seen the development of a variety of diseases which have

spread from one shrimp culturing nation to another. Aside from disease, the

development of acid sulphate soils has been cited as either a direct or indirect

cause of production failure These soils exist as 'potential acid sulphate soils'

(P.A.S.S.) in many mangrove areas, and as a result of the excavation and

construction of shrimp ponds P.A.S.S. may become actual acid sulphate soils

(A.A.S.S.). Upon wetting, these soils release large quantities of acid into pond

water and also toxic levels of iron and aluminium. Research in South East Asia

reveals that acid, iron and aluminium are directly responsible for fish and prawn

losses and general low productivity, (Simpson and Pedini 1985). Acid conditions

(and poor water quality in general) may indirectly cause production failure by

increasing physiological stresses, and decreasing the immune system response.

7.2 Environmental Condition of Abandon Shrimp Pond

The environmental conditions remaining after abandonment may be more

important than the causes of failure, and may be unrelated to the cause(s) of

failure. For instance in Malaysia, many ponds are said to be disused as a result

of white spot disease. However, the major obstacle to the redevelopment of

47


35/38

these ponds is not the prevalence of disease, but the remediation of acid

sulphate soils which may persist for many years after abandonment.

The ecological effects of acid sulphate soils have only recently begun to

be clearly identified. The acidic water which results from acid sulphate soils

destroys food resources, displaces biota, releases toxic levels of aluminium,

precipitates iron which smothers vegetation and microhabitat and alters the

physical and chemical properties of the water. Persistent alterations to pH have

been shown to lead to changes in the flora and fauna in an area, by favouring

acid tolerant plants and animals. This could have implications for attempts to

restore the mangrove ecosystem and its resident flora and fauna. Insufficient

research has been carried out to assess the number of shrimp ponds.

In addition to the activation of acid sulphate soils a further consideration,

unrelated to the causes of failure, are the alterations to soils which are likely to

occur as a result of the clearance of mangrove, shrimp cultivation and

abandonment. Ignoring the changes from shrimp culture which are likely to vary

with farming method and culture intensity, the effects of clearance and

abandonment may include accelerated soil erosion due to increased surface run

off and subsurface flow; decrease in soil water storage capacity; reduction in

biodiversity of soil fauna; transport of sediments, dissolved inorganic and organic

constituents and principal nutrients; and depletion of soil organic matter through

leaching and mineralisation.

48


36/38

The abandoning of aquaculture developments represents a significant

challenge to the productive use of coastal areas in the future because of the

limited land use prospects for vast areas of former rice fields and mangrove

forest. The rehabilitation of these areas is complicated by the fact that many of

the environmental conditions that once fostered the growth of mangrove forests

have been removed or severely altered. When considering options for

redeveloping disused ponds, it is important that the environmental parameters

remaining in a pond are identified. To date little work has been conducted to

elucidate the conditions found in disused ponds, or to identify what implications

these may have for future uses. Disused ponds are likely to be unstable and

actively deteriorating and may represent a risk to neighbouring habitats, and

unless managed may become progressively more difficult to rehabilitate or

restore. Means of assessing such risks should be developed.

7.3 Restoration of mangrove areas

There are now strong signs of an emerging mangrove-friendly mariculture

industry. This initiative, presently experimental and confined to Association of

Southeast Asian Nations (ASEAN) countries, involves the combination of

reforestation with culture of fish, crabs or shrimp. It is an attempt to develop and

disseminate responsible culture technologies. Mangroves are also being

promoted as environments for culture of mud crabs in pens, a technique that

eliminates the conversion of coastal areas to ponds. In the Philippines, crab

49


37/38

farming in tidal ponds is already an established industry and crab farming in

mangrove areas shows great potential.

According to Global Aquaculture Association (GAA), the exploitation of

mangrove areas for new shrimp farms has essentially stopped and many areas

are being reforested. Studies using satellite photos indicate that mangrove forest

areas actually have begun to increase in shrimp farming regions in Honduras and

Ecuador.. In a review of effects on mangroves, the GAA also claims that shrimp

farming has accounted for less than 5% of the mangrove loss, and further losses

due to shrimp farming have virtually stopped, due to regulatory and educational

efforts.

The 2003 synthesis report by the World Bank, NACA, FAO, WWF

Consortium report on Shrimp Farming and the Environment contains a section on

mitigation and restoration. Rehabilitation of mangrove areas that have been

cleared for shrimp farming has been undertaken in some areas. This is neither

difficult nor costly as long as an appropriate hydrologic regime can be re-created.

This is not easy, especially if shrimp farming has been accompanied by other

development activities, including the construction of canals and roads. At a

minimum, effective breaching of dikes is required. Where natural mangrove is

sparse, there may also be a shortage of mangrove propagates, in which case

mangrove nurseries may have to be established.

The possibilities for rehabilitation of degraded coastal systems were

discussed at the scientific International Workshop on the Rehabilitation of

50


38/38

Degraded Coastal Systems, organized in 1998. One goal of the workshop was to

bring together key research on habitat restoration in a range of tropical habitats.

Another was to evaluate critically the effectiveness of rehabilitation and to

provide a summary of the state of the art in Asia.

Options for Rehabilitation and Restoration

However, despite these potential difficulties there are examples of

conversions to other uses, some of which may be regarded as successful. In

Samut Sakhon large tracts of abandoned shrimp ponds are being converted to

non-agricultural land use, such as for housing estate and industrial

developments. The abandoned shrimp farms can be converted to salt farms or

fish culture operations and shrimp farms located near main roads have sold top

soil for construction projects.

Apart from the fact that vast areas of mangroves are cut, another

consequence of industrial shrimp farming is that there is a vast volume of waste

produced inside the ponds by the shrimps. Food eaten by shrimps but not

retained in their body ends up as waste. As the waste piles up, bacteria flourish

and consume the available oxygen. This can suffocate the shrimps and reduce

their growth. Intermediate waste products both of shrimp, ammonia and nitrite,

are toxic to shrimp, fish and other animals. In order to avoid this problem, the

water from inside the ponds is regularly removed out and the ponds are filled in

with clean water. This system results in the pollution of the neighbouring surface

waters

Documents

Impacts of Prawn Culture