The stage of aquaculture development in Indonesia vary greatly from one island to another and from one province to the other. The potentials for fish production from this source in the whole country remain high. In Java, parts of Sulawesi and parts of Sumatra where aquaculture has undergone many years of development the engineering problems involve (i) selection of site suitable for aquaculture expansion; (ii) maintenance of economically viable sizes of aquaculture projects; (iii) improving layout and construction specifications to be able to intensify production and/or practice improved techniques; and (iv) use of better equipment for maintenance and operations.
On the other hand in new areas of development the engineering aspects that need consideration are (i) segregation of aquaculture development zones based on suitability and environmental considerations; (ii) for individual projects, proper selection of sites for development; (iii) establishment at the outset, of an economically viable size of aquaculture unit suited for the type of operation intended; (iv) adopting appropriate layout and construction specifications for the type of aquaculture intended; (v) implementation of proper construction techniques to avoid future problems in management and for the maximization of production; and (vi) acquisition and utilization of the best developed equipment for construction and maintenance of the aquaculture farm.
Considering the above conditions of the aquaculture industry in the country, the following recommendations would be applicable to Indonesia:
Much of the success of aquaculture projects depends on the selection of suitable sites. In this respect the availability of water supply of good quality would be a major consideration. For brackish water fishfarms that depend on tidal water, moderate tidal fluctuations of 2 to 3 meters is desirable while vary narrow or those one meter or less and very high ranges or those above 4 meters will pose problems in the future management of the projects. If possible these latter situations should be avoided. Land elevation where construction is to be conducted should also be carefully selected to be slightly above the lowest tide and at least 0.5 meter below the highest tide (ANNEX 11). It is of course assumed that the other considerations concerning soil, vegetation, water quality, etc. have also been considered.
It should be a national responsibility to zone the areas where aquaculture development will be pursued. This should take into consideration site suitability, adequate allowance for buffer zones from open waters, drainage exits for flood waters, vegetation cover and natural nursery grounds for existing wild stocks. If this is done the mistakes committed in already developed areas not only in Indonesia but also in other countries can be avoided. It should therefore be a national policy to segregate such development areas.
The assumptions under this recommendation may change with time. However, considering present practice of extensive type management for existing brackish water aquaculture projects which has been found feasible in the region, areas of one hectare or less are too small for economic management considering that the same man/months will be required for this work as larger ones. The income derived would also be too small and there will be a tendency to subdivide the project into very small units thus wasting water space which could be used for culture. Projects of five and up to 10 hectares seem to be advisable as an appropriate family size unit. Properly laid out with rearing compartments of not less than one hectare each, such projects appear suitable for the management practice that is now known in the region. On the basis of this size units, modifications of the physical plant and intensification of operations can better be implemented.
The layout plan for brackish water fish farms will depend on type of management envisioned and the species intended to be cultivated. Experimental design will require equal sized and relatively small ponds deriving their supply of water independently from a common source (ANNEX 8, Figures 8a and 8b). Demonstration or commercial fish farm projects may have varied sizes and shapes of pond compartments conforming with the configuration of the given site. Of course such projects should provide for nursery, transition and rearing pond units in appropriate proportions (ANNEX 12). For projects where stock manipulation or the progression method of management are to be used, the appropriate layout to enable proper implementation of these management methods are detailed in this report (ANNEX 12 and Figure 12a).
After a thorough survey of the site for suitability and layout planning of the project, the gates to be used as water control structures will be ready for construction. Wooden or reinforced concrete gates can be used. In any case it should be emphasized that such gates should not have too wide opening so that they would be difficult to manage. One to 1.3 m wide opening has been found appropriate but not wider. If more than one such gates are needed, a double, triple or quadruple opening-gate of proper width may be constructed at one or more spots along the perimeter dike. The structure and installation of such gate is detailed in this report (ANNEX 10). One important caution that need to be taken in this regard is that the gate bottom should be as low as the lowest tide experienced in the site. Elevated gate bottoms result in seepage and erosion of the gate foundation with time such gates are less effective for flooding and draining as desired. If wooden gates are to be used, painting with antifouling paints like coal tar or better yet chemical treatment of the lumber with creosote or similar material under pressure will help in prolonging the life span of such gates. The design for a reinforced concrete gate is shown in Figure 10 a ANNEX 10.
Secondary gates (Figure 10b, ANNEX 10) of similar pattern but usually smaller than the main gates can be constructed for the water supply canals, catching ponds, rearing ponds and nursery ponds. Water control pipes of asbestos, palm trunks or assembled wooden boards can also be used.
The construction of the main or perimeter dikes as well as the secondary or internal dikes should be preceded by a thorough clearing and cleaning of the patch and immediate vicinity of the path of these dikes. Trees, roots, stumps and undecayed organic matter should be cleaned out of these paths. It is often preferable to remove also the superficial layers of the soil down to 20 to 30 centimeters as these layers are usually heavily loaded with organic matter.
A puddle trench of about 0.5 meter wide by 0.5 meter deep is required along the center path of the main dikes and advisable also in the secondary dikes. It is observed that this is well known but seldom practiced. It may appear unnecessary at first but it can prevent a lot of water management problems in the future.
It is preferable to construct the dike in layers until the desired height is attained. In the process the soil should be cleaned of any undecayed organic matter and should be carefully and constantly compacted.
The height of the dike should be above the highest tide or flood that occur in the site giving adequate allowance of at least 0.5 m for shrinkage. The dike should also be of adequate size so that it could hold water inside and prevent flooding from outside and with appropriate slope of at least 1:1 but not steeper. The secondary dikes can be smaller and with slightly steeper slope than the main dikes.
Mechanized construction of fishpond dikes is still under development in the region. The presence of cheap available labour however is conducive to the continued and predominant use of labour-intensive construction for aquaculture projects. If and when mechanized construction techniques becomes more developed it can be used for big scale projects but still the work has to be brought to completion by some form of manual work. Better system of manual construction are detailed in this report (ANNEX 13).
For brackish water fish farms it is not very essential that complete clearing and cleaning should be done in the entire site during the construction of the project except for the path of the main and perimeter dikes. Once the entire project is enclosed and the essential water control structures are installed the area can be flooded for initial management and production. It is observed that during this period the leaves of the mangrove trees fall off to the pond bottom when the trees start to die out which can add to the fertility of the pond bottom. The trees can be cleared in stages while the ponds are being managed for production from year to year until the whole project is completely cleared. It is advisable to clear small trees by closely supervised contract per area of about one hectare lots. If the project is forested by big mangrove trees, it is recommendable to thoroughly clear the area by mechanized tree puller. A device for this work is shown in this report (ANNEX 14).
Levelling of the pond bottom is necessary for proper production management of the project. A suggested procedure for this work is detailed in ANNEX 12 of this report.
Periodic draining and drying of the pond bottom is a desirable management procedure in brackish water fish farms. These neutralize extremes of pH, accelerate decomposition of organic matter in the pond bottom and help eliminate predators. It is advisable to drain and dry pond bottoms at least once each year or after each crop period when possible.
The use of water pumps is becoming more essential to carry out improved production techniques in brackish water fish farms. The suitable types to use, their installation and operation will be required. Their use is particularly useful in areas where the tidal fluctuations is small so that if there will be need of supplementing the volume of water brought in by the tide by pumping, or to drain water off from such ponds even if the low tide is not sufficiently low to do this, such process can be done. Pumps will also be required to drain off water during the construction and installation of water control gates and their foundations.
Suggested types of water pumps, installation, operation and care are detailed in this report (ANNEX 5 and 13). As pumps are very essential in the Jepara Central Java project, the pumps and their management in that project are fully discussed in this report (ANNEX 5). It will be noted however that the procedure suggested in the Jepara project can be applicable in other coastal fish farms. Both a heavy fixed type pump for general water control and portable type pumps which can be reapidly transferred and used in any part of the fish farm when needed are recommerdable.
As brackish water aquaculture is of long existence in the region, certain equipments and implements have been developed and used for the construction and maintenance of fish farms. It is interesting to note that variations exists in different areas even for implements used for the same purpose. Preliminary studies have been made on this during the survey with a view to suggesting the most efficient implement that has been developed in the region. A study of digging implements, for example, is discussed in this report (ANNEX 13). These studies need to be continued.
Mechanized method of pond construction is discussed in Section 3.1.6 above and also in ANNEX 13.
A more extensive survey of the potential sites for the development of brackish water aquaculture project was conducted in this country. This covered the whole of West Malaysia during the period of May/June 1975. The following discussions and specific recommendations are presented for this country:
As mentioned in Section 2.2 the traditional shrimp trapping ponds are the only commercial brackish water aquaculture ventures in the country. There is general lack of background and experience in brackish water aquaculture in the country. To expand, diversify and intensify this industry, there is need for training of extension workers and fish farmers. Additional methods to further increase the inflow of water utilizing the high tides and perhaps supplementing by pumps may help increase production.
It is also noted that there are scattered small-scale projects for the culture of other crustaceans and finfish, put up by private individuals as mentioned in Section 2.2 of this report. These should be encouraged, supported and monitored by the government. The expansion of aquaculture in their respective areas can very well start with success which can spark development in this sector.
To date it has not been decided on what species to experiment within brackish water ponds. Since pond bottom elevations should be designed to suit certain species (Chanos, about 30 cm; shrimp, around 1 m water depth) it is essential that experimental demonstration ponds be constructed - one in the West Coast, another in the East Coast with pond bottoms set as close to mean lower high water (MLHW) as possible in order to be able to culture the widest range of organisms possible by providing deepest possible water in the ponds which can also be drained dry when the need arises. In this way culture experiments in varying depths up to 1 or so meter can be undertaken.
There seems to be no question as to the rich shrimp fry resources in the Malaysian rivers and shores. Whether it be shrimps, mullet or milkfish, etc. that will give fish farmers best returns on their investments in culturing ponds remains to be seen and can only be brought about by experiments on brackish ponds. While there may be problems as to source of fry, acceptance by people, etc., in the introduction of species that are efficient food converters, yet the fact remains that we are approaching the day when our sea catch will continue to decline perhaps due to pollution and over-exploitation and the Asian table protein will come more and more from culturing in brackish and freshwater ponds.
At this stage, it is imperative that a firm policy be worked out before the distribution of areas to individuals and/or corporations with an object to put the perimeter dikes in places to afford the maximum area for operation. It might also be timely to decide what area sizes to grant the new pond owners (either 5, 10 or more ha) and such a module be the experimental demonstration pond to be constructed by the government. In the Philippines, a lot of money, time and effort are now expended to move the perimeter dikes and renew layout for maximum area utilization because of unsupervised pond design and construction at the start. It should be emphasized that a pond complex does not necessarily have to have geometric figures. Design should yield to natural water edge, mangrove formation and dikes placed where topographic survey shows a reasonable difference in ground elevations between compartments and also taking general wind direction into consideration. Cut and fill should be at minimum to reduce cost of construction.
It might be necessary for the government to do some river diversion or straigthtening to maximize area for ponds.
For the above reasons, it seems quite urgent for the government to lead the way and should have its own brackish water aquaculture ponds for experimentation and demonstration. It is evident that this has been recognized by the Fisheries Division for sometime as a site at Johore state, specifically that of Gelang Patah, has been selected and plans laid out for the purpose.
One constraint that can be foreseen in the massive pond construction in Malaysia especially on the West Coast, is the fact that the Forestry Division seems to be presently deriving good income from royalties for wood on the area which the Forestry may not forego. The starting pond developer may not be able to afford, at the start, the equivalent to present royalties) rentals to be imposed by the Forestry. However these are problems that can be resolved through overall government policies that need to be set.
A major portion of the work done in this country concerned the selection of sites suitable for aquaculture development. For this purpose a set of criteria were set and a weighted evaluation system was adopted. The results of the survey done in West Malaysia pointed to the comparative suitabilities of various sites visited which can serve as guide for future government action as well as that of private industry (ANNEX 7 and 8).
The specific engineering problem now being faced by this station concern the pipes conveying its main water supply. Recommendations to solve this problem are detailed in this report (ANNEX 9).
Due to recent land development works in the watershed area of the Gelang Patah proposed site, it was observed during the survey that prolonged turbid condition of the water in this area may adversely affect this project once developed. The increased number of industries developing in this region may also pose more problems in the future. If the project has to be developed in this part of the country perhaps a site further down the tidal stream in this vicinity should be considered. (ANNEX 8).
As possible alternatives the site evaluation survey revealed high rating sites in both west coast and east coast areas of West Malaysia. Of particular interest are (i) Tanjong Dawai in Kedah state in the west coast and (ii) Kuala Kerteh in Trengganu state in the east coast. The characteristics of these alternative sites are detailed in ANNEX 8.
In general Philippine brackish water fish farms are underconstructed. Their perimeter or main dikes as well as main water control structures are not very adequate for the combined effects of extreme high tides and periodic floods brought about by typhoon rains that occur in the country. In many cases premature harvesting of fish stock has to be done before the typhoon floods to prevent total losses; leftover stocks are for a gamble. Many fishpond operators however have now realized this danger and have started to build adequate pond structures. The development cost is much higher but this investment may turn out to be more economical on a long term basis.
Another engineering flow in fishpond planning and construction in various areas of the country is the tendency to utilize most of the space available in each site for the fishponds. In many instances this results in constriction or near closure of drainage exits of flood waters resulting in seasonal destructive flooding not only of the fishpond areas but also of nearby communities.
In recent planning of fishpond development, the idea of viable economic family size unit has received consideration. The development of large sites (500 to 10 000 ha per lot) for the fishpond estate scheme, by subdividing this site into optimum size units for the economic operation by an average size family (6 members) is being studied. The study is still in progress but it is beginning to appear that areas of 5–10 ha may be the minimum for this type of operation.
The specific engineering recommendations for the Philippines are the following:
From the experience of more progressive fish farm operators it is obvious that constructing fish farms with adequate construction specifications would be better investment than the prevailing practice of underconstruction. In order to avoid unnecessary extra expense the optimum construction taking into account extreme tides and seasonal floods from typhoon rains should be considered. Technical advice on this matter will be required.
Guidelines should be set and strict government control should be imposed so that the rivers, streams or estuaries which provide drainage exits of flood waters are not closed or constricted. Sometimes straightening these water courses during the initial construction stage can be helpful. In either case close government supervision and regulation should be imposed. Technical studies in this regard should also be conducted so that sound advise could be rendered. Such studies should consider topographic and area survey, extent and nature of watershed, flood levels, tidal characteristics, wind direction, etc.
Much of the future problems of fish farm operations can be avoided if a thorough multi-disciplinary technical survey can be made of sites to be released for fish farm development. Besides others, the team should include an aquaculture biologist, an engineer and an administrator (representative of government agency responsible for releasing site). Only suitable sites for fish production should be released, adequate allowance for flood drainage should be imposed and proper construction specifications should be advised. It should be emphasized however that such a team should work to facilitate fast decisions for the proper disposal of applied sites for its best use.
More studies on this aspect will be required. However it is becoming apparent that individual small units (5 ha or less) operating completely on its own would hardly be economic even for family subsistence operation. It may be recommended to operate at least 5 to 10 ha economically provided certain essential common services and facilities and close technical supervision are provided. The services and facilities needed include such things as road and transport facilities to pond site, common fish seed nursery or source, preprocessing or cold storage facilities, marketing facilities and provision for social ameneties such as schools, social and religious centres, health clinics, electric power, etc. The required funding for this scheme may be big but it can be the type that can contribute substantially to the economy of a region and at the same time provide socio-economic uplift to poor fish farming communities.
Inspite of inherent limitations and constraints Singapore continue to be active in the field of aquaculture. By necessity this activity is confined to the intensive rearing of high-priced species. This is being tried in the smallest possible space and towards brackish waters and in the sea utilizing net cages. Investigations are also underway to find the possibility of using cultivable species in the utilization and management of organic wastes and for environmental improvements.
The specific recommendations with engineering aspects for this country are enumerated below:
Due to the reluctance of shrimp trapping pond operators to intensify their management, other means to increase production from these ponds may be adopted. Based on the observation that shrimp postlarvae and juveniles generally congregate at the shallow indentations of the tidal stream adjacent to shrimp trapping projects, utilization of these areas to intensify entrance of more seed shrimps is recommended. This can be effected by increasing the water intake either by better use of high tides or perhaps by water pumps. Incidentally this procedure can also apply to the shrimp trapping ponds in Malaysia where the tidal fluctuations are nearly similar.
This site can be renovated to serve as experimental and demonstration fish farm of the government. Details of suggested layout modification is given in ANNEX 15. Because of the nature of the water supply it is advisable that a water control pump be integrated with the project. Such a pump can be both to drain from or supply to the ponds. This set-up is operated with the pump in conjunction with a specially constructed water control gate (Figure 15 a, ANNEX 15).
The management of tidal aquaculture projects in this country is greatly influenced by the low tidal fluctuation. This necessitates the maximum use of pumps.
The layout and construction of existing coastal fish farms can take further improvements. If the raising of finfish (milkfish, mullet, etc.) is to be promoted, modifications in the design and management of the ponds will be required. Likewise the Central Prawn Research and Training Station at Bangpakong, Chachoengsao province now in the process of construction can further improve its facilities. The pertinent recommend ations particularly on the engineering aspects for this country are as follows:
As previously cited, because of the low tidal fluctuations, push propeller type pumps (Figure 5b ANNEX 5) are extensively used in Thailand. However, the engineering side of this pump has not been worked out well. Propeller and bearing system should be improved. An airfoil design impeller will give optimum performance. Also there should be provisions against harmful vortexing effect. The rought formula for determining Horse Power (HP) to pump column size relationship should be based for this kind of Total Dynamic Head (TDH) - sum of suction and discharge heads) and current components on 5 square inch crossectional area to every reconditioned automotive advertised diesels horse power used. Given HP, tube size is equal to:
and
A properly designed and matched low-lift propeller pump may utilize 8 or more square inches of pump column crossectional area for every BHP (brake horse power). Impeller pitch can be so designed to have maximum output at 700 to 900 RPM. This RPM is especially desirable not only for efficiency but also to have good survival rate of shrimp seeds passing through the pumps from which shrimp ponds depend mostly for their stocking.
This possibility was discussed during the visit to the Klong Wan, Prachuap Khirikhan Fisheries Station. It was noted that milkfish fry are available during certain seasons in this area. Instead of using only small dip nets, improved fry catching such as those used in the Philippines and Taiwan, China are suggested.
For raising finfish such as milkfish, mullet, tilapia, etc. varied management techniques can be used. (Stock manipulation, by size, method; deep water plankton method; progression method (ANNEX 12).
This will require appropriate modification of the layout and construction of the ponds.
Polyculture of finfish species and shrimps may also be done to maximize production.
The engineering problems of this station were investigated and the following pertinent recommendations were rendered:
(i) In the dike construction the need for puddle trench and compacting or grouting appear essential.
(ii) It is observed that the dike slope is too steep. Considering the type of soil in the site, a slope of 1:1.25 is recommended.
(iii) The base of dike seem to be too narrow to be able to prevent lateral seepage. It is advisable that these be made wider.
(iv) The path of the dikes are not being thoroughly cleared of grass and other organic matter. These precautions are safeguards against water management problems in the future and should be strictly followed.
(v) The hollow-block-cement holding compartments for juveniles could be much improved if poured reinforced concrete were used. The difference in construction costs would be negligible as same forms can be used over and over again.
Like Singapore, Hongkong has to utilize high-prized species and intensive culture techniques for her aquaculture activities. Aquaculture operations as a means to utilize or recycle organic wastes are also considered. The specific recommendations for the aquaculture engineering problems in this area follows:
The recommendation to prevent flooding of this station consists in raising and enlarging the dikes and retaining walls of this station. Details on how this can be done are described in this report (ANNEX 16).
Barring calamities (oil spills, etc.) the economic and technical feasibility of raising fish in floating cages in protected coastal areas has been demonstrated. Survey in the area showed that the sizes, shapes and material for these cages are varied. With the development of this industry, a standard design appropriate and suited to the management practice and the species used should be investigated and recommended for adoption by fish farmers.
It was indicated that there is a potential for further expansion of aquaculture in the Tampak area, New Territories, Hong Kong. The government should take a hand in accelerating development but regulating construction in the area if it is decided to have this site developed. Appropriate layout and construction for intensive-aquaculture management should be used. Strict control to avoid obstruction of excess flood waters should be enforced.
The experiments being conducted in collaboration with the Department of Public Works on the Possible utili ation of partially processed sewage waters for fish culture is a wise step in this direction. Depending on the success of these experiments the design of sewage treatment plants taking into account the possibilities for aquaculture can be undertaken.
The long existing practice of duck-cum fish culture in this area is another practice wherein organic wastes and nutrients are recycled through aquaculture operations. More of this type of activities should be encouraged.
