Fish farm layouts that are properly engineered should strike a balance considering economy, functionality and aesthetics. Within a prescribed production management scheme, the layout must be economical. The basic principle is to minimize the number of gates, and the size and length of the main secondary and tertiary dikes and canals. But this should not sacrifice the biological requirements for suitable environment of the cultured species.
Fishponds should be planned in such a way that the length of the pond is positioned parallel to the prevailing wind direction. The wind direction in Southeast Asia is shown in Fig. 4.1 and the suggested orientation of the ponds is seen in Fig. 4.2. As such, the length of dike exposed to wave action is lessened, thus, the cost of repairs also less. The position also takes advantage of the wind energy in effecting good water aeration through mixing and circulation. However, in areas where very strong winds are prevalent, wind breakers are included in the design and layout of ponds.
Fig. 4.1 Wind direction in Southeast Asia
(After Tiensongrusmee, 1982)
Fig. 4.2 Layout of pond compartments
oriented to the prevailing
wind direction
(After Tiensongrusmee, 1982)
In general, the fish farm is an establishment which is composed of pond system and support facilities. The pond system usually consists of various compartments with specific uses such as nursery or fry pond, transition or holding stunting pond, production or rearing ponds and other features (catching, desilting food-growing ponds, etc.). Also a part of the system are the water control structure or gates, pipes or culverts and water supply or drainage canals. Each of these units should be properly located and fitted in the system in order to have ease in water management and manipulation of cultured stock.
On the other hand, support facilities consists of farm buildings, farm roads and road dikes, bridges, fish tanks, storage shed (for feed and equipment), chilling tanks, and other ancillary structures. Efficient organization of support facilities in relation to the pond system is of paramount significance in the overall developmental planning and operation of the farm.
Fish farms are located at convenient distance from the sea or river. In the Philippines, a sanctioned buffer zone of at leat 100 m from the sea to the main perimeter dike and 20 m along river banks is spared for ecological consideration as well as physical protection against flooding and wave action. The required buffer zone along the shoreline in Indonesia is 400 m.
Existing fishpond layouts, especially for a milkfish farm may have all or just a number of the following compartments depending on the layout requirements as dictated by the management scheme and cultured species.
Sometimes called fry box this is the smallest unit in a pond system usually 4 to 8 m2. Fry are first stocked in this pond for 1 to 4 days and then allowed passage to the nursery pond proper by just cutting open the small dike partition (Djajadiredja and Daulay, 1982).
The nursery pond is small in size, about 1 to 4 percent of total production area and usually square or rectangular in shape. It may be a single pond unit or made up of two, four, six, etc. sub-compartments which form the whole nursery unit. A manageable area ranges from 500 to 10 000 m2 per compartment, although 1 000 to 5 000 m2 is preferred (BFAR-UNDP/FAO, 1982).
The nursery is used for rearing the fry for at least 30 days (in the case of milkfish) before transferring into another larger pond. Rearing the fish in small area is more convenient and safer as it can be watched more closely and taken cared of more adequately.
Nursery pond should be located in elevated portion of the farm in the central or near the corner of a rearing pond compartment (Djajadiredja and Daulay, 1982). The most suitable place is where it can be easily supplied with new unpolluted water at all times when necessary and at elevation where it can readily be drained even during ordinary low tides (Alcantara, 1982).
Avoid locating nursery ponds directly adjacent to perimeter dikes. Crab holes and leaks that might occur during the rearing period will serve as exits of fry from the nursery pond to the river. These can also serve as entrance for predators and unwanted species into the nursery pond, causing further loss of stock.
From the nursery pond the fry is moved into the transition pond or directly into the rearing or production ponds.
The transition, holding or stunting pond is located adjacent to the nursery pond in order to have efficient and quick transfer of fingerlings. Depending on the management scheme, close to 10 percent of the total production area is usually allocated for this purpose. The fingerlings or post-fingerlings are reared here for varying periods before finally stocking them in the production or rearing ponds. The fish can be retained in the transition pond longer or up to a few months especially when the number of fry stock is sufficient for several cropping within the year. A manageable area for transition ponds ranges from 1 000–20 000 m2 per compartment but 5 000–15 000 m2 is preferred (BFAR-UNDP FAO, 1981).
This is also called growout pond. It is the largest compartment in the pond system occupying about 80 percent of the total farm area.
The bottom elevation of the rearing pond should be about 0.2 m lower than that of the transition pond but slightly higher than the Mean Lower Low Water (MLLW) or zero tidal datum. The pond bottom slopes toward the catching pond or water supply canal to facilitate harvesting of marketable-sized fish. A manageable size ranges from 1.0 to 10 ha per compartment although 2.0 to 5.0 ha is preferred. Production ponds for milkfish of 15 to 20 ha per compartment is common in the Philippines.
This pond serves as a concentration area or basin for the fish during harvest. It is constructed adjacent to the gate inside a bigger pond compartment. Catching ponds may be provided also for nursery ponds, transition ponds, and rearing ponds. The catching pond for the nursery and transition ponds is usually about 2 percent of the respective compartments' water surface area; for rearing pond, it is usually 1–1.5 percent.
This pond is optional and may be built, if deemed necessary. Named “kitchen pond”, it is a compartment set aside for growing live food organisms at high density. this is a recent innovation and is intended to augment the availability of food in fishpond areas where natural food organisms does not grow well or in farm set-up where high density stocking of cultured fish is used.
The simplest form of pond layout is that of a single compartment. More recently, improved layouts consisting of multiple combination of compartments have come to general use. Through the years of experience in pond fish production the pond operators have evolved and developed the arrangement and relative proportion of the various pond compartments that would fit into the system together with the appropriate production management scheme.
Pond layouts may be grouped into: (i) conventional; (ii) radiating; (iii) modular or progression; and (iv) multiple stock/harvest pond system (BFAR-UNDP/FAO, 1981 and Denila, 1976). Examples of these layouts are shown in Figs. 4.3 to 4.7 and Figs. 4.17 and 4.18. All of these, however, are intended for milkfish production and in general maintain shallow water that is required by fish food called “lab-lab” (a complex community of micro-benthic biota closely associated with pond bottom). However, combination of deep-water for plankton production and shallow water for lab-lab production is also being practiced. The basic characteristics or differences of these layouts are shown in Table 4.1.
Table 4.1
Comparision of various layouts of milkfish ponds
| Layout scheme (production: kg/year) | Nursery pond | Transition pond | Rearing pond | |
|---|---|---|---|---|
| 1. | Conventional (1 000–2 000) | 1 percent of total production area | 9 percent of total production area | 80 percent1 of total production area |
| 2. | Radiating | Same as above | Same as above | Same as above |
| 3. | Modular (1 800–3 000) | 4 percent | 6 percent | 80 percent1; there are three production process stage; each stage follows a ratio 1:2:4 or 1:3:9 (Figs. 4.6, 4.17 and 4.18) |
| 4. | Multiple stock/harvest (1 000–2 000) | 6 percent | No transition pond; instead holding canal for fingerlings is allocated for each rearing pond; 19 percent of every rearing pond |
1 Some 10 percent is used for canals, catching ponds and dikes.
Fig. 4.3 A conventional pond system with catching pond (CP), nursery pond (NP), transition pond (TP), feed pond (FP) and rearing pond (RP) (After Alcantara, 1982)
Fig. 4.4 Radiating type layout showing transition pond (TP) and rearing pond (RP) (After Denila, 1976)
Fig. 4.5 Radiating layout of Taman and Porong types of milkfish farm with division pond (D); rearing ponds (A,B & C); fry pond (E) and canals (After Djajadiredja and Daulay, 1982)
Fig. 4.6 A modular pond system in the Philippines showing rearing pond stages (RPS) with ratio of 1:2:4 and 1:3:9 (After Alcantara, 1982)
Fig. 4.7 Layout of a farm by multiple stock/harvest system showing fish holding canal (FHC) as added feature (After Alcantara, 1982)
The difference between the conventional and radiating type of layout is the presence of much longer canal and secondary dikes in the former than the latter. The short supply canal of the radiating layout is desirable from the viewpoint of economy in dike construction. It also serves as catching pond. However in the case of Indonesia, a division pond (D) precedes the production or rearing ponds (Fig. 4.5) instead of supply canal.
For most of the layouts, the space occupied by the partition and canal dikes is approximately 10 percent; this is exceeded when large dikes are constructed.
Thailand concentrates more in shrimp culture with practically no milkfish culture. Pond layout for shrimp in this country vary depending on the levels of inputs and rearing methods as traditional, semi-intensive and intensive shrimp ponds. Although inner canals are occasionally found in milkfish farm layout (as in Indonesia), shrimp ponds are characterized by the presence of extensive inner canal system. Transition pond is generally absent unlike in milkfish farm (Fig. 4.8).
Fig. 4.8 Layout of the traditional shrimp pond in Thailand (After Chalayondeja, Thornbuppa and Sikga, 1982)
The traditional shrimp pond usually has shallow depth of water of 70 to 90 cm with one inlet water gate at one end and one outlet gate in the other end. The production is usually 25 to 90 kg/ha/year (Fig. 4.9). This traditional pond is modified by constructing larger ditches, higher dikes and increasing water depth to 100 to 150 cm, and hence, the size of pump (Fig. 4.10). By doing so, production has increased by 200 to 300 kg/ha/year.
Fig. 4.9 Layout of a modified traditional shrimp pond; N,nursery and gates (inlet, G1 and outlet, G2) (After Chalayondeja, Thornbuppa and Sikga, 1982)
The semi-intensive pond has a removable nursery pen in the rearing pond where post larvae are kept for one month, then released into the pond.
The intensive ponds also have nursery ponds or pens which are also constructed within the rearing pond. Supplementary feeding and aeration are necessary for this type of rearing. Intensive ponds are generally small in area. Production from an intensive pond of 1 to 6 ha with ditch of 8 to 10 m wide and 1.5 m deep and with a water level above the berm of approximately 75 cm is 1 000 to 5 000 kg/ha/year (Figs. 4.11 and 4.12).
The requirements of the cultured species is always the basis for planning the layout and formulation of management scheme. Within limits, however, management techniques can be manipulated to enhance production without affecting the normal growth of species.
The modular or progression system is a typical example of a layout wherein the management scheme involving fish movement in the various compartments are prescribed. In this system, specified number of milkfish fingerlings from the transition pond are stocked in the smallest production pond, then moved to the next bigger then to the largest pond. Movement of fish in each production pond stage can vary but is usually done in about 30 to 45 days. When inputs and conditions for normal growth exist, by this time the weight of fish stock has at least double, hence, movement to an area twice as large than where the fishes are, is logical. This enables the fish farmer to make four to six harvests per year with food growing period of 2 to 4 weeks between crops.
The multiple stock harvest system involves stocking of two to four different size groups of fish at different times in the pond. After 20 to 45 days, the large ones are harvested by gillnet or by netting selectively the fish swimming against the current during water inflow known as “pasubang” method in the Philippines. Another batch of small fish replaces the harvested ones. Repeated harvests, thereafter, is done every 30 to 50 days.
Because of this prescribed management method, fish holding canal (FHC) for each rearing pond is added in the layout, instead of transition pond. This is to insure availability of designated size(s) of fish for the rearing of ponds (Fig. 4.7).
Another example is a flow through system of shrimp culture. The rate of water exchange is regulated depending on the density of stocking. Water must be available any time irrespective of the tide cycle; hence, a combination of pump and reservoir system (using a headpond) or just a pump system should be provided (Fig. 4.10 and 4.11). Gates and canals are also strategically located to effect good movement and circulation of water.
Fig. 4.13 Indicative layout for a 5-ha shrimp monoculture project
(After H.R. Rabanal, Personal communications, 1983)
When necessary such as in intensive shrimp monoculture farms, each pond compartment should have individual water supply and drainage outlets to make them independent from each other (Fig. 4.13). The location of water control gates depends primarily on the water management scheme. In general, main gates and secondary gates are positioned where entrance and circulation of water could be most efficient. Ordinarily, a single gate per pond connected to a canal provides passage for tidal inflow and outflow. In a flow through system, two gates located in opposite ends of the ponds are required. Although slightly expensive, narrow rectangular slope is desirable from the viewpoint of effective water exchange. Likewise, separate canals that accommodate inflow and outflow of water from the gates are provided (Figs. 4.9 to 4.14). Canals should be located where it could connect or serve the most number of pond compartments. The lengths of canals should be minimized without sacrificing the functionality of the pond and intended management scheme.
Water control gates and canals that are properly located provides ease in water management and reduces operational costs.
The desirable temperature for milkfish and shrimp ranges from 27 to 32°C and 28 to 30°C, respectively. During the dry season, the water temperature may increase, especially in the shallower part of the pond. Providing canals inside pond compartments deeper than the general pond bottom remedies the situation and serves as a hiding place for shrimp during critical pond condition. These canals are also suitable in milkfish ponds with generally shallow water, where polyculture with shrimp is desired. The ditches can vary from 0.5 to 1.0 m in depth (Fig. 4.15).
The use of division pond is popular in Indonesia. this compartment distributes the tidal inflow to the various ponds and provides independence in the operation of individual pond compartment. It is a common feature for rearing ponds (Fig. 4.5) and even in nursery farm systems (Fig. 4.16).
This is appropriate for the flow through system in shrimp culture. The pump raises the level of water in the reservoir even during low tide so that gravity flow through in the rearing pond of shrimp can be effected.
This may be located near the water source before incoming tide enters the ponds. It is intended to settle suspended solids carried by the inflowing water.
Wooden or concrete tanks with capacity of 1 to 5 tons are usually constructed near the catching pond. Newly harvested milkfish are dumped and immediately covered with crushed ice to chill them to preserve their quality and freshness. This serves also to wash the fish and reduce bacterial growth.
It is advisable to have road system which should reach at least the main gate and catching ponds for easy and cheap transportation. This can reduce marketing cost.
some space is to be set aside for houses of persons employed and as storehouses for feeds, equipment and other fish farm materials.
Fig. 4.14 Indicative layout for a 5-ha shrimp monoculture project
(After H.R. Rabanal, Personal communication, 1983)
Fig. 4.15 Indicative layout for a 10-ha milkfish/shrimp polyculture fish farm (After H.R. Rabanal, Personal communication, 1983)
Fig. 4.16 Layout of Jakarta and Kamal types of milkfish
nursery with division pond (dp); fry pond (fp);
transition pond (tp); and canal (c)
(After Djajadiredja and Daulay, 1982)
Fig. 4.17 Indicative layout for a 10-ha milkfish
monoculture grow-out project
(After H.R.Rabanal, Personal communication,
1983)
Fig. 4.18 Indicative layout for a 10-ha milkfish monoculture grow-out project (After H.R.Rabanal, Personal communication, 1983)
