PART 3
CONTRIBUTED PAPERS

SCS/82/CFE/CP-24

ENVIRONMENTAL CONSIDERATIONS FOR THE DEVELOPMENT OF COASTAL FISHFARMS IN THE INDO-PACIFIC REGION¹

by

P. Menasveta²

1. INTRODUCTION

Aquaculture can be one way of increasing the fishery production and thereby provide a valuable source of protein for the people and a good financial return to fishfarmers.

Aquaculture has a high potential for future development. This is because the production per unit are can be improved through advanced technologies. In addition, the new international law of the sea will affect the use of fishing grounds of some countries in some cases resulting in the marine fishery production of some of them. The loss of this production may be compensated for through coastal aquaculture development.

At present, a large acreage (about 800 000 ha) has already been developed for coastal aquaculture in the Indo-Pacific region. An additional area of over 1 million ha may be considered suitable for future development.

It should be noted, however, that aquaculture may not succeed in the entire area. Success of aquaculture projects depends largely on the proper selection of the site to be developed into ponds. Prior to the site selection, various environmental parameters should be taken into consideration. These are, for instance, climatic conditions, tidal behaviour, soil and land quality, vegetation, water quality and pollution problems.

2. ENVIRONMENTAL SETTING IN THE COASTAL AREAS OF THE INDO-PACIFIC REGION

2.1 Climate

Three general types of climates are noted: tropical rain, tropical savannah and tropical monsoon climate. The tropical rainy climate is typified by high temperatures and heavy rainfall throughout the year. No distinctive dry season is experienced and the precipitation in the driest mouth is greater than 60 mm. These climates are located near the equator and most coastal areas in Indonesia and Malaysia fall into this zone.

The tropical savannah climate differs from the tropical rain forest climate in three respects: the total annual precipitation is often less, in the annual rain pattern both a wet and a dry season can be distinguished, and the annual rainfall is less reliable and shows a wide range in the annual amounts. In the driest month, precipitation is less than 60 mm. These climates occur at higher latitude and next to the rain forest climates. Savannah climates are encountered in the Chao Phraya and Mekong deltas.

The tropical monsoon climate can be considered as intermediate between the rain forest and the savannah climates. It is typified by high annual rainfall but experiences a period with little precipitation. Throughout the year, adequate rain falls and is stored in the soil which enables the natural forest vegetation to grow through the dry season. This climate is encountered along the east coast of Vietnam and scattered areas in the region.

In the tropical, rainy climate temperature is less variable than precipitation. The yearly average temperature is generally between 26° and 28°C. Little variation of the solar altitude and an almost equal day length are the main reasons for the small variation of temperature throughout the year.

In the tropical rain forest climate both monthly and annual precipitation are usually in excess of monthly and annual evaporation. In the tropical savannah climates annual evaporation is generally also somewhat lower than annual precipitation but the dry season evaporation is always in excess of rainfall whereas in the wet season precipitation exceeds evaporation considerably.

Some data on precipitation, temperatures and evaporation are presented in Tables 1, 2 and 3, respectively.

¹ Contribution to the FAO UNDP-SCSP Consultation Seminar on Coastal Fishpond Engineering, Surabaya, Indonesia, 4–12 August 1982.
² Associate Professor, Department of Marine Science, Faculty of Science, Chulalongkorn University, Bangkok 5, Thailand.

2.2 Tidal behaviour

The astronomical tides in the region under consideration are generally rather weak with mean tidal range not exceeding some 3 m. Typical is the 3 m spring tidal range along the coast of southeast Sumatra. An exception are the tides along the coast of the delta of the Irrawaddy River in Burma with a mean range of 4.5 to 5 m. Small tidal ranges occur along the coast of Kalimantan, where in the mouth of the Barito River near Banjarmasin even the spring tidal range is not more than 1.9 m. Along the west coast of Peninsular Malaysia tides are stronger with a spring tidal range of 3.6 m at Kedah (north), 5.1 m at Selangor (central) and 3.6 m at Johore (south).

Table 1
Mean monthly and annual precipitation for selected areas (mm)
Source: Volker et al. (1978)

Table 2
Mean monthly and annual temperatures for selected areas (°C)
Source: Volker et al (1978)

Table 3
Mean monthly and annual free water surface evaporation for selected areas (mm)
Source: Volker et al. (1978)

In the area under consideration both diurnal and semidiurnal tides and also mixed tides occur. At a given station, the tide may be diurnal during spring tide and mixed during neap tide as shown in Fig. 1 representing recorded tides at Tanjong Buyut at the mouth of the Upang delta. South Sumatra.

Fig. 1 Diurnal and mixed tides at Tanjong Buyut (Upang delta) Source: Volker et al (1978)

In addition to the astronomical tides, some coastal areas are exposed to extremely high sea levels caused by storm surges. Storm surges are generated offshore by differences in barometric pressure and drag of the wind over the water in cyclone and typhoon areas. They are superimposed on the astronomical tides. In most of the coastal areas under consideration storm surges have only a minor effect on the tidal levels with the exception of the coastal areas around the Bay of Bengal.

2.3 Soil quality

The factors that give rise to different types of soil are climate, topography, time parent material, vegetation and biological activity, including man. The topography in coastal areas varies little, being mostly flat with slight depressions. However, a slight variation can have great influence as the degree of drainage give rise to different types of soils, including the accumulation of organic matter and the formation of peat. The parent material can vary from infertile coarse and fine sands to fertile clays and clay loams of marine or riverine origin with the alluvium derived from volcanic sources or basic rocks. Vegetation can have an influence as there are species which accumulate considerable amounts of sulfur and others like some mangrove which trap fine sediments and extend the coast-line with fertile clay or silty clay soils. Man's influence on the delta soils is largely by drainage and sometimes by irrigation and drainage. Saline soils are desalinized and soil with organic top layer have their organic matter reduced greatly. Quantities of sulfur in acid sulfate soil are washed out by irrigation and drainage and made into non-acid sulfate soils.

Broadly speaking, the coastal plain soil in the region can be grouped as follows:

• Non-acid sulfate marine alluvium
• Acid sulfate marine alluvium
• Alluvial sandy soil

• Organic soil

2.3.1 Non-acid sulfate marine alluvium. Most of the soil derived from marine alluvial deposits in calm waters like the Strait of Malacca or the Java Sea are clay, heavy clay and silty clay soils. The clay soils that are developed over recent marine-and estuarine muds and are in their natural state subjected to flooding by tidal waters. In their undisturbed condition, these soils have a neutral to alkaline reaction owing to the high proportion of dissolved salts which they contain.

2.3.2 Acid sulfate marine alluvium. The acid sulfate soil is typically a juvenile soil formed under brackishwater conditions. The soil is often found in depressions and is subjected to flushing with brackishwater when heavy rains and spring tides coincide. The soil has a sulfate odour and changes colour on exposure to air. Initially, it is dark in colour but on further drying deposits of sulfate compounds appear. These types of soil have a pH of less than 3.5 (soil: water = 1:2.5) and a water soluble sulfate content of not less than 0.1 percent within the first 50 cm of the soil. Where these conditions occur in deeper layers, the soil is referred to as a soil containing acid sulfate layers.

The acid sulfate layer can be detected by the presence of yellow deposits of jarosite and natrojarosite when the soil is oxidized by drainage or drying. It usually occurs in drained soil between the wet and dry season water-tables. Potential acid sulfate soil can be detected by chemical analysis.

The problem with acid sulfate soil is its acidity. The sulfur accumulates as pyrite (FeS_z) where the soil is more or less permanently waterlogged. On drainage the pyrite oxidizes fairly rapidly to sulfur and more slowly to sulfuric acid.

2.3.3 Alluvial sandy soil. Where granite hills occur near the coast or fast flowing streams carry sand to the sea, sandy soils are formed. On the east coast of Peninsular Malaysia coarse and fine sands are acted upon by waves to form low beach ridges running parallel to the coast. Sandy beach soils also occur in Sarawak, Sabah, Kalimantan and in the southern part of Thailand. In some areas the normal coast of mangrove on clay is formed later and the original sandy beach is cut off and occurs a few kilometers from the present coast.

The sandy soils in most cases have at least 80 percent sand and no more than 20 percent silt and clay. Some of them have no silt or clay and are mainly composed of fine and coarse sand. Sandy texture prevails throughout the profile, and the soil matrix is generally loose and structureless.

The sandy soils pose problems for their development for aquaculture. The amount of water retained by a soil depends upon its textural composition and sand does not hold water and tends to dry out rapidly.

2.3.4 Organic soils. The organic soils are characterized by their coarse woody or fibrous texture, high moisture content, low weight-to-volume ratio and acid reaction. They are the remains of vegetation, mostly trees accumulated under anaerobic conditions found in depressions. They are considered as problem soils owing to their very low fertility, acidity, subsidence on drainage and the presence of buried timber. The organic soil which contains more than 65 percent organic matter is called “peat”.

2.4 Vegetation

Generally, the kind of vegetation depends largely on soil types. For marine alluvial soil, there exists mostly mangrove trees. The kinds of vegetation which are usually found on sandy beach soil are grass, palm and coconut trees. From observation it appears that cashew nut trees thrive well on some sandy soil while some types of pine are well adapted. The kinds of vegetation on peaty soil are, for instance, palm and gelam forest (Melaleuca leucadendron). Nevertheless, of these three types of vegetation, mangrove trees are the most common in sites for the development of fishponds in coastal areas.

Mangrove trees occur at many places on tidal land, estuaries of rivers, deltas, bays of islands and sheltered coasts in the tropical and subtropical zones. They are found only in fairly well-protected areas on mudflats between the level of the peak spring tides and the lowest neap tides. These mudflats result from the combination of silt from the land and sand from the sea. So mangroves generally thrive in high rainfall areas where there is plentiful silt carried to the shore. The distribution and extent of mangrove areas in some of the countries of the Indo-Pacific region are shown in Table 4.

Table 4
Distribution and extent of mangrove areas in some countries of the Indo-Pacific region. Source: MacNae (1974)

* Based on Thailand Department of Fisheries data

In Thailand, the mangrove forests occupy the muddy sea-shores and the estuaries, covering an approximate area of 3 680 km². On the west coast of the Peninsula, the mangrove forest area is very extensive starting from Rayong Province down to the Malaysian border. This type of forest is also found on some coastal islands in the Andaman Sea. These mangrove comprise approximately 80 percent of the total in Thailand. On the west coast of Peninsular Malaysia and on Sumatra, Indonesia, the mangrove areas were estimated to be 3 000 km² each (MacNae. 1974).

In floristic composition, the mangrove forest is comprised of species numbering from 20 to 40, belonging to several unrelated families. They share similar habitat preferences and a similar physiognomy; they are similar in physiological characteristics and in structural adaptations, most of them having pneumatophores or “breathing roots”. Watson (1928) listed some 17 “principal” and 23 “subsidiary” species in the mangrove forests of Malaysian coasts. In Thailand, 36 species have been reported by Smitinand (1975). The data on mangroves in Thailand as well as in the Southeast Asian region were recently updated (Gomez, 1980; Piyakarnchana, 1980).

Mangrove forests along the coastal belts were considered a precious asset, and when properly managed could have considerable value. They played an important role in maintaining various forms of biological life not only in the area proper but also over a much wider area. They acted as silt collectors, thus, promoting accretion of the foreshore. They were good sources of timber, fuel and thatching material, supported a variety of fish and shrimps as well as other wild life, effectively reduced wave impact on coastal structures and lowered storm surge levels. On the other hand, there were often alternative development possibilities. Thus, after reclamation by bunding, the former mangroves could be used for various purposes, including fish and shrimp ponds, but adequate care should be given to prevent unnecessary damage to adjoining ecosystems.

2.5 Water quality

Several water quality parameters in the coastal areas which should be taken into consideration are temperature, salinity, pH, dissolved oxygen and nutrients such as nitrate and phosphate. Generally, in the undisturbed coastal areas of the Indo-Pacific region, annual water temperature variation ranges from 24°C to 30°C, depending on seasons and areas. Salinity may range from 0 to 32 ppt. Salinity of the coastal area which is very near to river mouth is usually affected by freshwater runoff during the rainy season. The pH of coastal water is slightly alkaline (pH>7.0). However, soil condition in the mangrove swamp could lower the pH value of water significantly. The water properties of the coastal mangrove area in the Gulf of Thailand were studied by Aksornkoae et al. (1979). The details of their findings are shown in Fig. 2. It is interesting to note that certain physico-chemical properties of water, such as temperature, pH, salinity and dissolved oxygen were higher in the open water than in the dense forest. The nutrient (phosphate, nitrate and silicate) did not show significant change between the open water and the forest area.

2.6 Pollution problems

Large-scale forest clearance for agriculture and resettlement, uncontrolled timber exploitation, land reclamation for industrial and residential estates and construction of harbours and highways have given rise to widespread soil erosion. Where such developments were located inland, the resultant silt from the top soil was washed into the riverine systems and eventually carried down to the sea. In coastal developments, the eroding material reached the sea by direct terrestial runoff. Coastal and estuarine waters have thus been constantly subjected to varying degrees of sedimentation, a phenomenon very noticeable in the Strait of Malacca.

Fig. 2 Average values of water properties at different locations from forest margin to the land in a mangrove forest (From Aksornkoae et al., 1979)

In Thailand, sediments from erosion in the amount of 1.5 × 10⁶ tons year are concentrated at the mouth of the major river systems emptying into the northern part of the Gulf of Thailand. This has resulted in a vast delta (3 695 km²) in the Gulf of Thailand. Reforestation is presently being implemented.

In Indonesia, siltation is recognized to be a serious problem which can adversely affect subtidal marine communities, especially in the vicinity of the river mouths. Soil erosion occurs mainly on the island of Java owing to its high population density of more than 500 inhabitants/km² and intensive agricultural activities in some areas, such as the Brantas River region. It has caused coastal accretion or “delta” build-up along the northern coast. Therefore, many milkfish ponds are presently being reclaimed for paddy field. Sumatra and Kalimantan have siltation problems too. Their soil erosion is due mainly to deforestation associated with the lumber industry.

Leaching of agricultural lands, particularly those in the coastal areas could have transferred significant quantities of pesticides, fertilizers and undegraded organic matter (e.g., wastes from canning factories and rubber processing factories, and peat soil) to the coastal area by rivers and drainage canals. These factors will adversely affect the water quality of the coastal areas.

Owing to the continuing dependence of tropical countries on agriculture, the use of pesticides will undoubtedly tend to increase probably in close correlation with the steady increase in population. In general, the use of pesticides for most countries parallels the increase in agricultural output, except for chlorinated hydrocarbons, which have decreased because of the universal knowledge of their persistence in the environment coupled with legislation against their use.

There has been a general decline of riverine fisheries in the rivers on the west coast plains of the Peninsular Malaysia and in the coastal part of Thailand over the last few decades. Although this effect may be attributed in some ways to an increase in exploitation of fisheries, a deterioration in the water quality of these rivers, resulting from increased sedimentation as well as pollutant loads from domestic, industrial and agricultural outfalls, has contributed significantly towards such an effect. Incidents of large-scale fish mortality in streams and rivers have been reported frequently from such activities as man's deliberate use of poisons and explosives to kill fish and the discharges of toxic effluents from agricultural land. A case of mass fish kill was observed in a drain-age canal in Nibong Tebal. Penang, Malaysia in April 1965 owing to a sharp drop in the pH of water (less than 4). This was presumably caused by runoff of weedicides from an adjacent coconut plantation (Jothy, 1976). Riverine fishermen have reported a decline in giant river carp in the rivers Sungai Perak and Sungai Pahang. This fish has now been listed as an endangered species (Jothy, 1976). The considerable decline in production of giant freshwater prawn in the Chao Phraya River and Lake Songkhla is presumably due to runoff of pesticides from adjacent agricultural areas coupled with wastes from cities. A considerable decline in ricefield fishery has been felt by farmers. A study carried out in an area under rice cultivation (the Krian District of the State of Perak) has shown as much as 50–60 percent decline in the fishery during the period 1969–1971. The decline in fishery is mainly due to agricultural advances leading to the use of increasingly potent pesticides in pest control (Tan, et al., 1973).

In the well-developed agricultural lands, there are many agro-related processing plants located in the areas. These plants include sugar-mills, canning factories, rubber factories and tapioca mills. They do not acquire proper waste treatment systems, hence they contribute large quantities of undegraded organic wastes into the receiving waterways and adversely affect the aquatic ecosystem.

In Thailand, cases of mass fish kills were observed in Mae Klong River and its estuarine area during the dry seasons in 1970–1973. The damage was estimated to be approximately US$1.5 million. This was due chiefly to waste water from 12 sugar-mills located on the river bank. In the lower section of the Brantas River, East Java, it was reported that there were 70 factories located on the river bank; 13 of them are sugar factories. The decline of fishery production in Madura Strait is presumably due to industrial wastes coupled with pesticide residues from the Brantas River.

The peaty water or “black water” from the recently developed tidal swamps such as Delta Tamban Luar (Kalimantan) and Delta Batang Berbak (Sumatra) could alter the ecosystem of the receiving rivers. The peaty water has a very high biological oxygen demand (BOD), which can decrease the oxygen content of the river water to a level which is intolerable to aquatic life. The depletion of dissolved oxygen in some sections of the river could intercept the migration routes of some economically important species, such as Macrobrachium rosenbergii.

Inland gravel pump mining in the mangrove forests is one aspect of resource utilization. However, such an operation when carried out improperly can lead to the destruction of land fertility. The land that has been under mining operations can no longer support vegetation and instead becomes a “waste land”. In Thailand, approximately 40 000 hectares of mangrove forest have been used in mining operations.

The problems and constraints delineated above have shown that changes in one part of the ecosystem may have impacts on the structures and functions of the other parts. It is therefore, imperative that the aquatic and terrestial environment be protected from further deterioration so that it is able to regenerate or recover from any form of environmental damage, well in advance of a situation that causes irreversible damage.

There is a need to establish baseline levels of pollution in waterways and coastal seas and to monitor them in the hope that information derived from such investigation would serve well in advance, as a warning against levels of pollution that may be detrimental to human, animal and aquatic life. The environmental quality standard is considered to be essential for the establishment of laws and regulations on waste disposal.

3. ENVIRONMENTAL REQUIREMENTS FOR COASTAL FISHFARM DEVELOPMENT IN THE INDO-PACIFIC REGION

The success of aquaculture depends to a large extent on the proper selection of site to be developed into ponds. The types of areas that should be avoided as sites for coastal fishponds are as follows:

• sites where the soil is sandy or rocky or both;
• sites which are too elevated and reached only occasionally by extreme high tides;
• sites overgrown with or forested with large-size trees;
• sites located in areas with very great tidal fluctuations (5 m or more) or those with very small tidal ranges (1 m less);
• sites located in areas with intense acid sulfate soils and containing too high organic matter (peaty soil); and

• sites located in areas which are very near industrial complex zones or highly populated zones.

The sites that are rocky or sandy are unsuitable because these would be difficult to work and after construction the management of the water supply — either overflooding or uncontrolled draining — would be a constant problem.

There are certain sites that appear to be swamplands but on close survey are found to be barely reached by the very high tides of the year. These are difficult areas because they would require much excavation work to bring them to a workable elevation for management as fishpond. Besides, even if excavation can be conveniently done, the question of where to dump the extra soil often presents another big problem. Of course, in some cases, the extra soil can be used to build big main dikes, and pumps may be used to bring the needed water, but this will lead to high costs of operation.

Forested sites with old and big trees are quite common in many tropical swamplands, especially as swamps become more elevated owing to yearly accretion and silting. Although these types of sites can be developed under a long-range programme, the expense involved in thoroughly preparing them for aquaculture would be great and a long period of time would be required before production from this type of land can be fully realized.

There are many areas in the world where the daily and the annual ranges of tides are very great, so that tidal fishpond construction would be impractical. Areas where the daily or monthly tidal range usually reaches as much as 5 m or more are not generally advisable for development into fishfarms. In these areas, the absolute range of tides during the year may reach as much as 10 m. Under these circumstances, extremely big dikes requiring much soil will be needed both to withstand pressure from outside during a very high tide and to prevent total drainage during a very low tide; and any mistake in the water management by the fishfarmer in this case can produce disastrous results. However, coastal areas with a tidal range of more than 5 m are not common in many countries of the Indo-Pacific region.

Coastal areas with acid sulfate soil are not uncommon in many tropical regions. Although these types of areas are not suitable for fishponds, some of the areas where the acidity is not so intense can be used for fishfarms after reconditioning the pH of the water by limiting or flushing processes. Also certain design modifications can be made. A good example of aquaculture development in an acid sulfate area is the Rangsit area (Thailand). Areas with peaty bottom and high acidity such as Tamban Luar (Kalimantan) are not suitable for aquaculture development.

Industrial wastes from industrial complexes and domestic wastes from highly populated areas could alter the coastal environment significantly making it unsuitable for aquaculture. There are two types of adverse effects resulting from industrial and domestic wastes, i.e., the direct effect which is the toxicity of the wastes themselves and the indirect effect such as oxygen depletion. Besides, such wastes may result in the over-eutrophication of coastal water, causing “red tide” which is detrimental to the cultured species.

4. REFERENCES

Aksornkoae, S., C. Lebaak and S. Ketupranee. 1979 Nutrient cycling in mangrove forest. Research Report to the National Research Council of Thailand, February 1979: 47p.

Gomez, E.D. 1980 The present status of mangrove ecosystem in Southeast Asia and the impact of pollution — Regional. FAO/UNEP, SCS/80/WP/94: 102p.

Jothy, A.A. 1976 Report on marine pollution problems in Malaysia. International Workshop on Marine Pollution in East Asian Waters, Penang, Malaysia. 7–13 April 1976.

MacNae, W. 1974 Mangrove forest and fisheries. Indian Ocean Programme, FAO, Rome. 35p.

Piyakarnchana, T. 1980 The present status of mangrove ecosystem in Southeast Asia and the impact of pollution — Thailand. FAO/UNEP, SCS/80/WP/94e: 108p.

Smitinand, T. 1975 Vegetation and ground cover of Thailand. Department of Forest Biology. Kasetsart Univ. (mimeograph).

Tan, C.E., C.B. Jack, S.H. Koon and T. Moulton. 1973 A report on paddy and paddy-field fish production in Krian, Perak. Ministry of Agriculture and Land Reform, Malaysia, 58p.

Volker, A., K.K. Kanapathy, C.P. Lambregts, S. Sujadi and P. Menasveta. 1978 Development of marshes, lagoons and tidal land (including flood control) in humid tropical areas. Background Paper, p. 68–148 in Proceeding of the Third Regional Symposium on the Development of Deltaic Areas. Water Resource Series No. 50 United Nations, 1978.

Watson, J.G. 1928 Mangrove forests of the Malay Peninsula. Malaysia For. Rec. 6: 275p.

SCS/82/CFE/CP-21

AN INTEGRATED APPROACH TO THE SURVEY, INVESTIGATION AND STUDY OF COASTAL FISHPONDS PROJECTS¹

by

C.K. Khoo and T.O. Wuan²

1. INTRODUCTION

Unlike in some of her ASEAN neighbours (notably Indonesia and the Philippines), brackishwater aquaculture has not been practised traditionally in Malaysia. The shrimp ponds that operated over the last few decades in the south-west part of the peninsula cannot be truly categorized as a form of animal husbandry; it is more of a trapping process. Of late, however, due to diminishing returns from its marine fisheries, the Government has begun to focus more attention on coastal aquaculture as a means of increasing its coastal protein resource and in safeguarding the livelihood of fishing communities affected by poor catches.

In view of her long shoreline accommodating a relatively vast extent of tidal swamp, the potential for coastal aquaculture in Malaysia is apparently great (total area of mangrove forest in Peninsular Malaysia is about 110 000 hectares). The Government has conducted several studies on development of medium and large-scale fish and prawn culture projects in this ecosystem of which a few are in various stages of implementation. The authors have participated in a number of such programmes involving site identification, feasibility studies and pond designs and construction.

In this paper, we wish to relate the procedures we adopt in selecting suitable culture sites within a large study zone and in conducting feasibility studies of proposed projects at such sites. Our system of selection and evaluation, though generally on the same line as those put forward by Jhingran, et al. (1970), Jamandre, Jr., and Rabanal (1975), SCSP/SEAFDEC (1977), ASEAN (1978), and New (undated) is executed on a multi-disciplinary approach encompassing aquacultural, ecological, engineering, socio-economic, management and financial aspects.

2. THE APPROACH

The coastal areas with potential for brackishwater aquaculture in Malaysia are almost exclusively mangrove swamps and these habitats shall be our point of attention in this paper.

In carrying out a study to identify and to assess the viability of sites for aquaculture, we begin by conducting a general pre-feasibility appraisal of various pre-selected areas of the study zone. Following this, the sites are evaluated in terms of suitability utilizing a weighted point system similar to that used by Jamandre, Jr., and Rabanal (1975). The site adjudged with the greatest potential in each zone of study is then thoroughly investigated by a team comprising of aquaculturists/ecologists and engineers/hydrologists whose recommendations are subject to further evaluation by socio-economists and management and financial experts. All findings are then integrated into a report presenting background information and the environmental condition of the study sites, the proposed pond system and engineering works, the recommended farm management procedures and finally a financial analysis.

3. THE GENERAL PREFEASIBILITY APPRAISAL

This study is based on a combination of three approaches, namely:

1. Review of existing site information;
2. Field surveys; and

3. Interviews

In reviewing existing site information, the respective government departments are approached for up-to-date records as follows:

1. Survey Department: Topographic maps;

2. District Office: Land ownership, developmental plans;

3. Fisheries Department: Catch statistics, aquacultural activities, water quality;

4. Drainage and Irrigation Department: Hydrological and water quality records, ground elevation;

5. Agriculture Department: Soil survey records;

6. Forestry Department: Acreage of mangrove forest, main species, nature of exploitation, if any (whether alienated or not, type of activities, etc.)

7. Meteorological Department: Rainfall pattern, evaporation rates;

8. Division of Environment: Water pollution status; and

9. Marine Department: Tidal characteristics, water current pattern.

Other useful information are obtained from publications and reports from local universities and governmental research institutes.

¹ Contribution to the FAO UNDP-SCSP Consultation Seminar on Coastal Fishpond Engineering, Surabaya, Indonesia, 4–12 August 1982.
² Consultants in Aquacultural and Environmental Research and Development, Equasian Sdn, Bhd., Kuala Lumpur, Malaysia.

Such a review may immediately rule out as unsuitable certain sites thus saving considerable time and effort by doing away with the actual field inspection.

As for the field survey and interviews, these are normally brief and are conducted concurrently to obtain specific localized information and to fill in unanswered questions left from the information review. In the field survey, basic water and soil parameters are examined and simple measurements are taken for ground level with respect to heights of high and low water.

The following parameters are examined:

1. Water quality (measurements are taken during high spring tide of surface and bottom water)

   1. Visual observation (colour, turbidity and odour)
   2. Depth
   3. Temperature
   4. Salinity
   5. Dissolved oxygen
   6. pH

   7. Total suspend solids

2. Soil quality (samples are taken at surface and 1 m below)

   1. Visual observation (colour, texture and odour)
   2. Soil composition (including organic matter content)

   3. Fresh pH

3. Tidal range and general ground level are measured using a simple depth stick and with reference to corrected water heights from tide tables.

Other information which are obtained from the field include accessibility of the site, estimated land price, general topographic features, location of creeks and rivulets, types of mangrove vegetation and availability of utilities, feeds, spawners and fry.

Interviews with the local inhabitants are taken to gather complementary information. Sometimes entirely new findings are discovered such as in connection with security, and peace and order at the site. Also useful is localized knowledge of seasonal variation in environmental conditions especially with regard to water quality and meteorological conditions.

A questionnaire incorporating the various information required for the assessment is presented in Annex 1. The information obtained from the site information review, interviews and field survey is then qualified through a weighted point system to arrive at a score indicating the potential of the assessed site. From this exercise, the sites within the study zone are categorized, according to the point values, into three general groups, viz.:

1. Sites with good potential
2. Sites with some potential

3. Sites with little or no potential

Depending upon the actual requirements, one or more sites categorized as having good potential are then subjected to detailed feasibility studies.

4. THE FEASIBILITY STUDY

4.1 General

At the feasibility level, the environmental conditions of a selected site are investigated more intensively than in the general study. Pending the favourable outcome of the suitability of the site, aquaculturists will then select the culture system(s) most appropriate for the environment. After this, engineers will design the general physical layout of the proposed aquaculture system taking into consideration the environmental characteristics and the species under culture. Such a plan is prepared only to the degree required for estimation of engineering cost. An implementation schedule together with the expected production and requirements for seeds, feeds and fertilizers is then drawn up. Along with the recommendation of the management system and a projection of the strength of the management and labour force required, projected cash flows are drawn for financial analysis of the proposed project.

4.2 Field surveys

A detailed field survey, covering more parameters and where samplings are taken at greater frequencies and at closer stations is conducted at this stage. The parameters examined are:

4.2.1 Aquacultural aspect

1. Water quality (measurements are taken during high and low spring tide and high and low neap tide of surface, middle and bottom layers of the water body)

   1. Visual observation (colour, turbidity and odour)
   2. Depth
   3. Temperature
   4. Salinity
   5. Dissolved oxygen
   6. pH
   7. Total suspended solids
   8. Biochemical oxygen demand
   9. Chemical oxygen demand
   10. Plankton analysis (biomass and species diversity)

   11. Pesticide residue level

2. Soil quality (samples are taken at the surface, 1 m and 2 m below surface)

   1. Visual observation (colour, texture and odour)
   2. Soil composition (including organic matter content)
   3. Fresh pH

   4. Air-dried pH

4.2.2 Engineering aspect

1. Topography

   1. Spot heights at ground level (measurements are taken from at least two survey lines)

2. Soil investigation (hand-augered samples up to 3 m depth)

   In-situ field tests

   1. Permeability test

   2. Vane shear test

   Laboratory tests

   1. Visual and manual examination
   2. Moisture content
   3. Liquid limit
   4. Plastic limit
   5. Plastic index
   6. Linear shrinkage
   7. Particle size distribution
   8. Specific gravity
   9. Bulk density
   10. pH test
   11. Sulfate content
   12. Organic content
   13. Unconfined compressive strength
   14. Triaxial test
   15. Consolidation test

   16. Permeability test

In addition to the water and soil quality survey, the aquaculturist team will study in detail the following factors:

1. Aquatic fauna, especially with regard to the kinds of predators, competitors and pests likely to be present.

2. Availability of feeds, whether in the form of processed grain by-products, trash fish, formulated feeds, etc.

3. Seed supply situation, whether from the wild, from commercial hatcheries or to be imported. The need for hatcheries to be constructed at the site may be considered.

4. Pollution threats likely to be present, e.g., from effluent discharge of factories.

5. Impact of the aquaculture scheme on the existing environment.

The engineering studies at this stage will also include hydrological studies to determine magnitude and frequency of upland flow of nearby rivers, their discharge being liable to affect water quality of the site. Stage frequency studies are also conducted by use of standard hydrological procedures of run-off estimation in conjunction with stage hydrographs. Tidal studies to determine the stage duration frequency relationship are carried out by gauging at the site when such records are not available.

4.3 Aquaculture system, production and engineering works

4.3.1 General

The relevant site parameters and characteristics being made known, this phase of the study is concerned with the advocation of a suitable culture system and a projection of the farm output.

4.3.2 Aquaculture system

In assessing the biological aspect, the following factors are considered:

1. Species to be cultured and whether monocultured or polycultured
2. Intensity of culture
3. Culture period per crop
4. Types and requirements for seeds, feeds and fertilizers
5. Pond management procedures

6. Projected production rate and production volume

Species to be cultured may be shrimps such as Penaeus monodon or P. merguiensis or fish like Lates calcarifer. Epinephelus or Siganus. In any single pond complex, a few species may be farmed either on a monoculture or polyculture basis depending on seed availability and the market demand. Due to the relative inexperience of local farmers, an extensive or semi-intensive level of culture is normally recommended. It is also important for an estimation of the seeds, feeds and fertilizers to be made not only for the purpose of assessing the operational cost but to ensure that sufficient amounts of these materials are available. Criteria for seed requirements are based on stocking density and estimated mortality while that for feeds is based on established feed conversion ratios. Since the study site may cover a large area, it may be necessary to phase out operation of the ponds over a few years as it may not be practical to commission all the ponds in a single year due to constraints relating to availability of skilled labour and supply of seeds and feeds. Finally, an estimate is made of the production rate from which the production volume is projected.

4.3.3 Engineering works

The engineering input will be on planning and design of the ponds and costing of capital works. Detailed plans are not necessary and preliminary plans are prepared for the purpose of estimating the capital expenditure involved. The factors considered are:

1. Siting of ponds
2. Layout of ponds
3. Types of dikes
4. Supply and drainage canal system
5. Water control structures

6. Buildings and ancillary structures

Pond layout will be influenced by the shape and size of the project site, the presence of access roads, the source of water intake, the need for mangrove belts to act as buffer zones, the presence of dissecting creeks and the actual ground elevation.

The number and size of ponds are considered with regard to the proposed culture system, capital cost and size of the site. Ponds are normally designed rectangular in shape. The length to breadth ratios are normally upwards of 2:1 for ease of construction and harvesting. Perimeter canals may be included for the same reasons.

For dikes, the height, width and side slopes of perimeter, secondary and tertiary dikes are designed with relevance to the site topography and soil structure.

The layout and size of canals will take into consideration the volume of water, frequency of exchange and whether the same or separate canals are used for both supply and drainage.

The type of water control structures considered include gated culverts, open flumes with drop boards and turn-down pipes. Their sizes will depend on the exchange frequency and rate of water flow. The need for pumping facilities is also considered.

Buildings and ancillary structures will include office, storeroom, quarters, guard house, field shelters, foot bridges, etc. A typical list of the capital works and equipment used for cost estimates is presented in Annex 2.

4.4 Socio-economic, management and financial studies

4.4.1 General

Information derived from the aquacultural and engineering studies is utilized for the formulation of the appropriate management system. From a knowledge of the financial inputs and outputs, cash flows are projected for the operation of the proposed project over a definite period from which its economic viability is evaluated.

4.4.2 Participants and the management system

In deciding the system for participation by smallholders, farmers and fishermen, the following issues will be considered:

1. Whether aquaculture is going to be his main source of income;

2. Whether the participant is willing to be relocated to participate in the project;

3. Whether the participants are working full-time or part-time in the project; and

4. Who are the likely participants in the project.

Information from the district offices and any existing information pertaining to the socio-economics of the project will be taken into account.

The management of these fishfarms will be tied with the method of participation. A choice will be made of the three principal options for participation:

(i) Estate farming

Under this system, all participants will be employed by the aquaculture farm solely to provide the necessary labour to operate the various activities. These participants are paid a regular wage but are not eligible to participate in the profit sharing. The aquaculture farm will be managed centrally by professionals and skilled personnel.

(ii) Individual aquaculture farm ownership

Under this system, each participant will independently own the aquaculture facilities he is operating. He is the sole decision-maker and he is responsible for all farm and management decisions.

(iii) Owner participation with centralized control

Under this system, the participants are all co-owners of the project. The aquaculture project will be managed by a project team which coordinates and supervises all farming operations. The participants themselves will be responsible for the operation and maintenance of all on-farm structures according to procedures laid down by the project management. The participants will be paid a daily wage and are eligible for profit-sharing.

4.4.3 Financial analysis

Based on the development plan for the proposed project, a financial analysis is undertaken, taking into account all capital and operating costs and income from the scheme. This analysis is carried out to fulfill the following objectives:

1. To assist in the preparation of a farm budget and in the projection of participants' income to see whether it can meet the participants' income expectation.

2. To assess the economic benefits and costs of the aquaculture project and to generate all related financial statements and cash flows.

3. To compute the internal rates of return (IRR) for the project including the relevant sensitivity analysis.

The capital costs will include all common facilities like utilities, pumping installations, access roads, office, quarters and ancillary buildings, ponds and capital replacement. Operating costs will cover costs of seeds, feeds, operating and maintaining the ponds and other installations, labour and management.

The sensitivity analysis is carried out to gauge the sensitivity of the project to fluctuations in benefits and costs.

5. CASE STUDIES

We summarize below the findings of two feasibility studies carried out for the Ministry of Agriculture, Malaysia utilizing the methodology described above (EQUASIAN, 1981). One of the sites is located on the west coast of Penang Island in the north of Peninsular Malaysia and the other is located within the Sungei Pulai mangrove complex in the southwestern part of Johore State in the south. In both cases, the studies revealed that the proposed projects are economically viable.

6. REFERENCES

ASEAN. 1978 Manual on pond culture of penaeid shrimp. ASEAN National Coordinating Agency of the Philippines, Ministry of Foreign Affairs, Manila, Philippines, ASEAN 77/SHR/CUL 3, 132pp.

EQUASIAN SDN. BHD. 1981 Study for aquaculture development for Western Johore, Malacca and Balik Pulau/ Seberang Prai Integrated Agricultural Development Project. Volumes I–IV.

Jamandre, T.J. and H.R. Rabanal. 1975 Engineering aspects of brackishwater aquaculture in the South China Sea Region. South China Sea Fish. Dev. and Coord. Prog. Manila, Philippines. SCS 75 WP/16. 37pp.

Jhingran, V.G., G. Krishnan, P. Ray and A. Ghosh. 1970 Methodology for survey of brackishwater areas in India for coastal aquaculture. Indo-Pacific Fisheries Council, Bangkok, Thailand, IPFC/C70/SYM 31, 37pp.

New, M.B. (undated). The selection of sites for aquaculture. Kelvin Huges Aquaculture Services, Bucks, England, 16pp. (mimeograph).

SCSP/SEAFDEC. 1977 Joint SCSP/SEAFDEC Workshop on Aquaculture Engineering. South China Sea Fish. Dev. and Coord. Prog. Manila, Philippines, SCS/GEN/77/15, 453pp.

ANNEX 1
SITE SURVEY QUESTIONNAIRE

ANNEX 2
A TYPICAL LIST OF CAPITAL WORKS AND EQUIPMENT REQUIRED FOR COST ESTIMATES OF A POND PROJECT

1. Pond construction

1. Site clearance and destumping
2. Excavation for ponds and dike formation
3. Inlet and outlet gates

4. Strip turfing

2. Water supply and drainage structures

1. Asbestos cement pipes
2. Main control gate

3. Secondary control gates

3. Pumping installation

1. Civil works
   1. Intake channel and sump

   2. Pumphouse

2. Equipment
   1. Pumps and motors (or engines)
   2. Electrical installation (not necessary if diesel engines are used)

   3. Pipeworks and specials

4. Quarters

5. Office/laboratory-cum-store

1. Earthworks
2. Buildings
3. Spot turfing

4. PVC chaining fencings

6. Ancillary works

1. Guard house
2. Foot bridges
3. Field shelters

4. Mooring jetty

7. Services

1. Access road
2. Water supply
3. Electricity supply

4. Sewerage and drainage

SCS/82/CFE/CP-22

THE PROBLEM OF PREDICTING SEASONAL AND LONG-TERM VARIATIONS IN PARAMETERS AFFECTING SITE SUITABILITY IN COASTAL AQUACULTURE¹

by

J.M. Kapetsky²

1. INTRODUCTION

This brief paper gives some observations on important aspects of coastal aquaculture site selection which are not sufficiently emphasized in books and papers on the subject, and therefore are worth calling attention to here separately.

2. SOME PRACTICAL CONSIDERATIONS FOR COASTAL AQUACULTURE SITE SELECTION

I have been asked to contribute some observations on site selection based on recent experience in Malaysia on this topic (Gedney, Kapetsky and Kuhnhold, 1982) and this I highlight in the following paragraphs. First considered are the overall criteria through which sites are evaluated. Then we move on to considering two of the most difficult aspects of coastal aquaculture site evaluation; prediction of seasonal and longterm changes in environmental quality.

2.1 Coastal aquaculture site selection criteria

It seems worthwhile to point out here as prelude to what follows that the basic parameters for coastal aquaculture site selection and site evaluation are essentially the same no matter the means of culture to be practiced, the animal (or plant) to be cultured, or whether the cultured product is for immediate consumption, or for further grow-out. This perception is illustrated in Table 1. which shows some common kinds of coastal aquaculture in the Asian tropics and organisms cultured and considers these against criteria for site selection or site evaluation. It readily can be seen that common to all kinds of culture are considerations of water quality, water quantity, seed and feed availability, shelter or protection, technical infrastructure, and underlying all of these, economic and welfare considerations.

Most of these parameters can be checked through fairly routine measurements or procedures in “real time” through the on-site field investigation. However, it is when projections have to be made to account for seasonal and long-term variations that site evaluation becomes increasingly difficult.

2.2 Prediction of seasonal and long-term variations in quality of the environment as a problem in coastal aquaculture site selection and coastal aquaculture engineering

Ultimately, the process of coastal aquaculture site selection or site evaluation leaves an element of uncertainty as to the future suitability of a site. It is well known that water quality and quantity can vary greatly both seasonally and in the long-term. Repetition of field measurements over a seasonal cycle, while desirable, is apt to be excessively costly, hence, evaluations are often based on measurements made relatively close together in space and time. It is still more costly and difficult to obtain time series which would permit reasonable extrapolation of conditions a few years ahead.

For the future, practical contributions in fields such as application of modelling trophic status in relation to nutrient loading (e.g., Rast and Lee, 1978), a better understanding of interactions of water chemistry in coastal systems such as mangroves (e.g., Boto and Bunt, 1981), as well as practical modelling of water quality conditions in fishponds (e.g., Romarie Boyd and Collins, 1978; Krant, Motzkin and Gordin, 1982), if integrated, could considerably aid in predicting the suitability of a site by inputting seasonal and long-term weather data. However, such forecasting for site selection purposes is probably still far off, and meanwhile use will have to be made of less sophisticated methods such as those proposed below.

2.2.1 Prediction of seasonal variation in water quality and quantity for coastal aquaculture site evaluation

Some of the sources of seasonal variation in water quality and quantity are obvious, such as local rainfall, and therefore the source of information for prediction of possible effects of, say, floods on water quality (e.g. salinity, suspended matter) is equally obvious (meteorological records, records of the entity dealing with irrigation and drainage). In other cases, prediction of seasonal effects will require deeper investigation. An example here may be the possible direct effects of agricultural pollutants such as pesticides on cultured organisms. Pesticides usually are applied seasonally and therefore concentrations of pesticides reaching water inputs to culture areas or fishfarm sites may also vary considerably. Should on-site measurements be made at a low-point in pesticide concentration, then an important factor in site evaluation could be incompletely evaluated with possible future serious consequences for culture activities. At the very least, interviews of nearby farmers will indicate at what time of the year and what kind of pesticides are applied. Reference to literature³ will indicate whether or not the pesticides used are harmful to cultured organisms, or if taken up by the organisms, if these are ultimately dangerous to man, the consumer.

¹ Contribution to the FAO UNDP-SCSP Consultation Seminar on Coastal Fishpond Engineering, Surabaya, Indonesia 4–12 August 1982.
² Fishery Resources Officer, Inland Water Resources and Aquaculture Service, Fishery Resources and Environment Division, Fisheries Department, FAO Rome.
³ For example, UNEP's “International Register of Potentially Toxic Chemicals”

Table 1
General site selection parameters for various types of coastal aquaculture

If the results of tests for residues in the sediments are inconclusive, ultimately, it may be necessary to schedule tests measurements of pesticide presence and concentration based on the timing of heaviest seasonal inputs.

The most straighforward means to get at possible seasonally occurring water quality difficulties at a site is to make a reconnaissance of the area surrounding the prospective site by land or by sea to note if there are any obvious potential sources of pollution.

Then, based on the kinds and locations of possible pollution sources identified one can judge how this pollution might vary seasonally. For example, in a water supply receiving domestic pollutants, concentrations might be expected to be highest during the dry season when flows are lowest. In contrast, agricultural pollutants may be the most serious at the beginning of the rainy season when large concentrations may enter water supplies in a “slug” which has been washed out of crop areas in which pesticides were concentrated during the dry season during the first heavy rains of the season.

The seasonality factor in site evaluation brings up an important aspect of evaluating variations in water quality and quantity. It is not monthly or weekly averages which are important. Rather, it is the extremes which have the most conditions that the ultimate suitability of the site should be evaluated. Mok (1982), for example, in discussing site suitability for cage culture, advocates frequent surveys throughout the year to account for seasonality factors. However, where this is not possible, taking observations at the extremes of wet and dry weather, of neap and spring tides, and in calm periods and storms is advocated.

2.2.2 Coastal aquaculture site suitability in the long-term

Probably, one of the most difficult parts of evaluating the suitability of a coastal aquaculture site is whether it will remain suitable throughout the expected or designed life of the farm or project, a time span which may be measured in one decade or two or even longer for some kinds of culture.

Two activities are recommended. Local government (or higher) authorities involved with development and planning should be interviewed to enquire about the kinds and pace of development activities which could influence the future suitability of the site. Secondly, development patterns in the vicinity of the proposed site should be studied. Large-scale maps can be used to determine the drainage basin in which the site is located, and hence the geographical area from which landward dangers to the site might stem. In the former, local authorities will have a good idea of the development activities planned or being sought for the future. These could include local light or heavy industries. expansion of various kinds of agriculture, or plans for expansions of urban centres or ports. Something as simple as trends in population in the district in which the proposed site is located, if available, may give valuable insight into future development trends and their consequences, such as domestic pollution loads. Interviews with local businessmen and personal observations of the distribution of agriculture and population centres could constitute useful familiarization activities before engaging busy officials in interviews. Help may also be obtained, for some districts, by consulting economic geographers, or their publications.

Unconsciously, one tends to think of coastal aquaculture site suitability as mostly determined by landward events or situations. However, it is important to look along-shore and seaward for possible developments in navigation or marine commerce which could also influence site suitability water quality in the long-term. Among possible problems the perturbations might be oil discharges, increased turbidity, erosion from propeller wash, and the like.

Reconnaissance may have to be from the water rather than on land, and reference may have to be made to published information on long-shore currents, wind and storms to judge the danger of coastal sources of pollution such as effluents from factories or food processing plants being carried to the site.

2.2.3 Aquaculture site selection “trade-offs”

A final observation on coastal aquaculture site selection is that the process involves trade-offs. Therefore, site evaluation does not really lend itself to rigid numerical rating systems for comparing sites even though quantitative and semi-quantitative point systems for this purpose have been designed (Gedney, Kapetsky and Kuhnhold, 1982)

The reason that site selection at best can be semi-quantitative is that not all criteria have equal weight (e.g. water quality versus available technology) and it is difficult to assign weights objectively. Furthermore, the same criterion or parameter may have a different weight from one site to another site. For example, the need to provide a social benefit, such as job opportunities, can vary significantly from one community to another.

3. REFERENCES

Boto, K.G. and J.S. Bunt 1981 Dissolved oxygen and pH relationships in northern Australian mangrove waterways. Limnol. Oceanogr., 26(6): 1176-8

Gedney, R., J.M. Kapetsky and W.W. Kuhnhold, 1982 Training on assessment of coastal aquaculture potential. Malaysia. SCS/GEN/82/35. 62 pp.

Krant, J., F. Motzkin and H. Gordin, 1982 Modelling temperatures and salinities of mixed seawater fishponds. Aquaculture, 27:377–88

Mok, T.K., 1982 Selection of suitable sites for cage culture. In Report of the training course on small-scale pen and cage culture for finfish. SCS/GEN/82/34. 99–102 pp.

Rast, W. and G.F. Lee. 1978 Summary analysis of the North America OECD eutrophication project: Nutrient loading-lake response relationships and trophic state indices. Ecol. Res. Ser., EPA-600 13-78-008. 455 p.

Romarie, R.P., C.E. Boyd and W.J. Collins, 1978 Predicting night-time dissolved oxygen decline in ponds used for Tilapia culture. Trans. Am. Fish. Soc., 107(6):804-8