Fish farming is not entirely the application of knowledge on how to make the fish survive and grow. Much of the success in the commercial growing of fish lies in the proper application of engineering principles.
In today’s article, we will note down a list of seven helpful tips for constructing your fish pond, and the differences between Sugpo & Bangos farming.
MAKE A THOROUGH STUDY BEFORE YOU BUILD A COMMERCIAL FISHPOND
Pay close attention to the layout, design and construction of your ponds. A well-built fishpond means lower costs and better production, says Mr Leonardo Denila of the Western Visayas Federation of Fish Producers, Incorporated.
Artificially built ponds are subject to natural forces especially waves and flood waters. But with proper design, layout and construction, the harmful effects of floods and waves can be prevented and minimized.
Here are the preliminary steps in constructing fishponds.
Observe the tides
Observe and note down the tide levels, especially during June, July, November, and December when tides are influenced by heavy rains. The highest and lowest tide levels will affect the elevation of ponds. Also, find out the levels of flood waters from the people in the locality. This information is important in determining the height of your main dike.
Familiarize yourself with the season in the locality
Familiarize yourself with the wet and dry seasons and the cropping schedules in the locality as these will help you properly manage the fishponds. For the repair of gates and dikes, for stocking and harvesting, you will need extra labour. Schedule them when you can get enough local labour – usually before and after rice planting
and harvesting and after the milling season for sugar. Know the local customs and traditions because these will greatly affect labour costs.
Take note of the soil topology before construction
Construction costs will also be affected by the kind of plants that had been growing or are growing in your fishpond site and by the type of soil. Sandy clay or sandy loam is best for dike construction because it is hard and does not crack when dry. Don’t use soil formed from decayed bakawan roots because it easily burns when dry. Also, avoid using completely sandy soil because it is the most expensive to transport. Besides, “lablab” grows poorly with sandy soil.
Take note of the water source for your pond
Meanwhile, your main source of water supply should be noted. Your pond water may come from the sea, rivers or creeks but the presence of a freshwater source is an advantage because it would enable you to have control over the salinity of pond water.
Control of salinity is very important for the growth of fish and fish food. See to it that the water is not polluted by wastes coming from such establishments as sugar centrals, distilleries, sawmills, and other factories.
Follow guidelines on the layout, design and construction of the pond
For the layout, design and construction of fishponds, consult with knowledgeable and experienced fish farmers and with the technologists of the Bureau of Fisheries.
They can give you useful guidelines so that you won’t have to spend so much on building and, afterwards, in making repairs.
HOW TO DETERMINE WHAT WATER LEVEL IS GOOD FOR FISHPONDS
Good water management depends on the water elevation of the fishpond site. Water elevation can be determined by making actual measurements of the height of the water in the site at different stages of the tide and comparing these measurements with the expected heights from the predictions in the tide table.
You can obtain a copy of the tide table from the Bureau of Coast and Geodetic Survey, Barranca St., Manila. For example, if the actual height of the water in the site is four feet when the prediction listed in the tide table is four feet, then the elevation in the said area is 0.
If the area has six feet of water when the prediction is four feet then such an area has an elevation of two feet. On the other hand, if the area has one foot deep of water when the expected tide level is four feet, that area is three feet above 0 datum.
The suitability of an estuarine area for a fishpond project based on the water supply can be summarized as follows:
1. Sites with elevation from 0 to 3.5 feet make the ideal elevation for fishponds because they can be watered or drained even under ordinary tidal conditions. Those at an elevation from 1 to 4.5 feet are also suitable for fishpond purposes.
2. Areas at elevation 4.5 to 7 feet can be suitable only if they are excavated while areas between -2 feet to -1 foot are suitable only if filled.
3. Areas above 7 feet are unsuitable because they are not watered. Areas below -2 feet are also unsuitable because they are always underwater and it would be too expensive to fill them up unless they get elevated by natural forces.
WHAT MAKES A GOOD NURSERY POND OR SEMILLAHAN
The nursery pond should be prepared at least one month before stocking. This is especially true if fry is to be stocked, after acclimation, direct to the nursery pond.
A good nursery pond should have the following features:
1. It must have a low and level bottom to permit water to flow from the sea or river even at low tide.
2. Its bottom soil should have an organic matter content of at least 16 per cent; soil pH must be from 7 to 8; and there must be a good layer of clay in the subsoil to retain water.
3. The pond should have two water gates for easy entry and exit of water from the supply canal to the drainage canal.
4. The pond bottom should be inclined towards one water gate for easier collection and capture of young fish.
5. The pond should have a peripheral canal of at least 15 centimetres deep for fast draining of water while the central portion is being prepared. This canal also serves to catch soil, dirt and other matter falling off the dikes to prevent pollution of the feeding zone.
6. The nursery should have strong perimeter dikes to avoid seepage due to holes caused by crabs or eels and to avoid overflows during heavy rains and typhoons.
STRUCTURES THAT PROTECT BANKS AND PONDS
Waves, water currents and wind action can gradually erode dikes and embankments you may not even notice the effect until it is too late. To be sure, build protective structures such as breakers, jetties and barriers.
SEAFDEC engineer Rodolfo Tolosa gives the following means of protecting your pond from strong waves, water currents and wind action:
1. Breakwaters could be either rubble-mound, wooden-type, or a buffer zone of mangrove trees. A rubble mound is made of stones or boulders while a wooden-type one is formed by driving two lines of mangrove piles and filling the space between these piles with branches of trees. A mangrove buffer zone can be established by planting mangrove seedlings in places that have to be protected.
2. Jetties arranged in a zigzag pattern prevent scouring at river bends. Coconut trunks or bamboo may be used. The space between the jetty and the river bank must be filled with twigs and branches. Jetties serve to cushion the impact of onrushing waters on the shore, especially at river bends.
3. Embankment protectives. Internal waves eat away at embankments unless you set up barriers. Some of these barriers may be made of bamboo wave breakers, worn-out rubber tires, and ripraps. A cheap and effective method is to grow creeping or close-growing grasses on embankments.
4. Screened barriers. The mouth of pond gates can be clogged by debris. To prevent this, set up a screen barrier before the gates. Bamboo or nylon screens installed at a distance before the mouth of the main gate will collect the floating debris.
USE LOW-COST MATERIALS TO BUILD PONDS
Cheaper and locally available materials could be used in constructing ponds, especially nursery ponds. Although laborious to prepare, they will cost much lower and are just as durable as the ready-to-use but costly materials, according to Flor Apud of the SEAFDEC Leganes brackishwater research station.
For instance, PVC materials which are normally used for distribution lines can be replaced with a canal system made of bricks and hollow blocks, Apud said. Wooden pipes or bamboo poles can be used as inlet or outlet pipes instead of PVC materials. Other usable materials are coconut trunks and big bamboo poles.
USE A WATER SUPPLY PIPE INSTEAD OF A SLUICE GATE
For prawn nursery ponds, use a water supply pipe instead of a sluice gate. This is according to SEAFDEC researcher and nursery pond design expert Flor Apud. Apud says that while a sluice gate is practical and efficient in grow-out ponds or bigger ponds, its use is impractical in the smaller prawn nursery pond.
Firstly, it is expensive as it requires bigger and more materials.
Secondly, its maintenance cost is rather high because you’d have to periodically change the flushboards and parts of the sidings which rot easily. And thirdly, water seepage is strong in wooden sluice gates.
This problem of water seepage can be easily controlled with the use of small pipes, says Apud.
For a small nursery pond, a wooden pipe or bamboo pole can easily supply and control water and yet it is cheaper and more practical, Apud says.
ACID SULFATE SOILS – A BIG PROBLEM FOR FISHPOND OWNERS
Many fishpond owners are getting very low or even zero productivity because their ponds have acid-sulfate soils. What are acid sulfate soils?
These are soils that contain a good amount of the mineral called pyrite. Pyrite is an iron disulfide in crystal form.
A pond site may contain a good deal of pyrite although the acidity of the soil may not be immediately evident because, as long as pyrite is submerged in water, it undergoes very little change. However, upon draining the pond site and excavating the soil, the mineral pyrite comes in contact with air and combines with oxygen (to undergo a process called oxidation) to form sulfuric acid.
When pyrite-containing soil becomes very acidic it. is called acid sulfate soil. Acid sulfate soils are not productive and may require a large amount of lime – as high as 20 to 100 tons per hectare — to neutralize.
Acidic soil has also a high phosphate-fixing capacity which means that phosphorous, an essential element for the growth of plants like algae, gets locked in the soil and is not made available to plants.
The acid also attacks other soil minerals to release such minerals as iron, aluminium and manganese in active forms. These minerals in active form limit the availability of other soil nutrients. Hence, you find in extremely acid sulfate soils not even algae growing.
You are advised to have the soil of a proposed fishpond site, especially the subsoil, analysed to find out if you have an acid sulfate or a potential acid sulfate soil. Go down to as deep as one to two meters to obtain your soil sample.
If your site is identified as having an acid or potential acid sulfate soil, a decision has to be made as to whether you proceed with its development. Excavating the area to a depth that would take advantage of the tidal fluctuation must be weighed against the cost of excavation as well as the cost of conditioning the pond soil to neutralize the acidic condition.
The cost of using a water pump must also be considered if you decide to have a shallow pond bottom. A shallow bottom could avoid getting down into the soil layer where pyrite is found.
Some of the suggested measures to neutralize acid sulfate soils include the following:
(a) repeated drying and flushing of the pond soil with seawater
(b) applying burnt lime in sufficient
(c) covering the excavated pond bottom with more
(d) good water management which controls the water table in the pond to limit the oxidation of pyrite and acid formation
(e) controlling the erosion of dike soils by planting grasses or shrubs tolerant to acid like African grass and a local Cynodon species.
THE BASIC DIFFERENCES BETWEEN SUGPO FARMING AND BANGOS FARMING
A profitable combination in fish farming is sugpo and bangos. There are two ways of doing this, according to Mr Ricardo S. Esguerra, a fish culturist and researcher of the SEAFDEC Aquaculture Department.
One is the traditional method which could yield 1,000 kilograms of bangos and 300 kilograms of prawns per hectare per year. The other, using the improved technique of raising prawns, can yield one ton of prawns and 300 kilograms of bangos in a hectare per
year. Here, a much higher profit is expected because of the higher price for prawns.
Esguerra pointed out the need to know the basic differences between bangos fanning and sugpo farming. The following are some of these differences:
1. Bangos ponds usually do not need any specific size or shape. The size of rearing pond compartments ranges from 5 to 20 hectares. On the other hand, prawn ponds must be long and narrow with an area of one to two hectares and arranged in a northeast-southwest
direction. Such an arrangement takes full advantage of wind action for pond water aeration.
2. Because of the extensive nature of bangos fishponds, dikes must measure from 3 to 5 meters at the base and 2 meters in height.
Dikes for prawn ponds are larger: a base of 5 to 7 meters and a height of 2 meters to maintain water as deep as one to one-and-half meters.
3. Each milkfish pond requires only one gate for every ten hectares, while prawn ponds must have an inlet gate and an outlet gate to achieve water flow-through.
4. Bangos ponds need clay-loam soil suitable for lablab growth. Prawn ponds, on the other hand, must have soft sandy clay soil so that the prawns could easily dig and seek shelter.
5. Intensive prawn culture requires aerating devices such as air blowers and pumps. Bangos farming does not need these except when the oxygen level is low.
6. Bangos ponds need clear water to produce good lablab growth. For prawn ponds, green water is preferable to prevent cannibalism.
7. While bangos pond water has to be changed every two weeks, prawn ponds need a change of at least one-third of the total volume once a week.
8. Bangos fry may be stocked directly into the nursery pond in one corner and after an hour the fry would spread out all over the pond. When sugpo are stocked in one corner of a pond, they stay in the same spot so that a predator could easily wipe them out.
Sugpo fry should therefore be distributed in small numbers all over the pond.
9. Bangos are not susceptible to diseases. Occasionally, parasites attack them during periods of high water salinity. Prawn fry, on the other hand, is susceptible to fungus and bacterial infections.
10. Bangos may be shipped iced or frozen. Sugpo may
be shipped alive in dry sawdust. For export shipping, prawns are beheaded, deveined, and blast frozen.
Modern Aquaculture for the Philippines by Ceferino de Los Santos, Jr., 1978
Design and Construction of a Prawn Nursery Pond by Flor Apud and Madrid A. Sheik. In, Readings in Pond Culture and Management. SEAFDEC Aquaculture Department, May 1978.
Prawn pond engineering,” R.T. Tolosa. Technical Consultation on Available Aquaculture Technology in the Philippines (proceedings), SEAFDEC Aquaculture Department, Feb 1979.
The Philippines Recommends for Bangos 1976
Layout, Design, Construction and Levelling of Fishponds”, Leonardo Denila, Readings on Aquaculture Practices. SEAFDEC Aquaculture Department, May 1977.