Fixed cages are very easy to construct and only require a small amount of capital investment. The materials needed to make fixed cages are netting with an 8mm mesh size, bamboo, rope, twine and sinker. Routine management is difficult for these cages and storms, strong currents, tidal surges and flooding may cause damage if precautionary measures are not taken. Fixed cages are difficult to move from one place to another during water fluctuation.
A top cover is usually provided on cages to reduce the risk of fish escaping, especially in areas prone to flash floods where water levels rise very quickly. A small opening is kept at one edge or in the middle of the top covering for feeding purposes. A feeding platform made of fine mesh is placed on the bottom of each cage to minimize food loss. To fix the cage, four bamboo poles are fixed in the substrate and the four top and bottom corners of the cage are tied to the bamboo poles with nylon rope, allowing the cage netting to stretch.To minimize installation cost and to reduce daily management labor, cages are sometimes fixed in rows with a narrow space between the adjacent cages.
A. Floating Cages
The size of the cage is usually 1m3. A top net is always used to minimize escapees because the cage is only a few centimeters above the water surface. The top of the cage is on hinges that can be opened to allow feeding, the checking of fish, the removal of waste and harvesting.
A layer of fine mesh net is placed along the bottom of the cage and 10 cm up each side which reduces food loss. However, where water has a high turbidity, the use of fine mesh is not recommended as it clogs up the mesh and causes structural stress on the cage frame. In these areas, feeding trays should be used instead of fine mesh. Buoyancy is achieved by using four plastic floats (buoys) which are tied to the four horizontal frames, approximately 10 cm from the top of the cage.
B. Bamboo Frame Cage
To make a 1m3 bamboo cage, twelve one meter long bamboo sticks (about 2cm in diameter) are required and fixed into the holes of the angles, one angle for each corner, giving a box shape.
Advantages and disadvantages of fixed and floating cages
Fixed Cages
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Floating Cages
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Advantages
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Advantages
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| Disadvantage | Disadvantages |
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C. Cage Management
Care of Cages. Cleaning of aquatic weeds nearby, removal of water hyacinth, cleaning of waste feeds from cages, cleaning of deposited silts from the cage, removal of dead fishes, checking cage frames, floats, ties, anchors, feeding trays etc., cage shifting, considering the water level, checking water pollution and guarding.
Care of Net. Algae attachment should be cleaned at regular basis to ensure water exchange, net holes must be checked properly and need quick repairing when necessary.
Care of Fish. Profitability depends on proper attention to the fish growth, regular, adequate and quality feeding is important. Fish health and disease should be monitored during feeding and sampling. The fish must be fed daily using aquatic weed or a mixture of rice bran, oil cakes, kitchen waste, chopped snails or cow dung.
D. Minimizing Risk of Cage Culture
- Appropriate cage design can help minimize failure.
- The use of more than one cage per household greatly reduces the risk of an individual losing all fish.
- Placing many cages together in clusters also reduces the risk of poaching.
- Individual farmers can form groups that can guard the fish and therefore considerably reduce potential poaching threats.
Fish is an important part of the diet for the people in rural areas providing protein calcium, fatty acids, and vitamins.
Traditionally, a variety of local species were used in ponds, mainly carp, caught from the wild as spawn (fertilized eggs or small fish). One of the main drawbacks of this source of supply is that along with the desired fish species come many undesirable ones.
Most of the species currently used in the cages are exotics. However, for decades these fish have bred naturally and distributed themselves throughout the floodplains and the delta.
A. Common Fish Types
The selection a suitable fish species will depend on various biological and economic factors, such as;
- Market price
- Growth rate
- Ability to reproduce the simple culture of young fish
- Match of fish and available fish feed
- Water temperature is an important criterion in assessing which fish species is suitable.
Some fish are more suitable to pond conditions than others, some fish will not adopt the confined conditions while others such as the indigenous Koi (Anabas testidunous) have been found to thrive in cages.
B. Small Indigenous Species
In addition to the main cultivated species, there are many indigenous breeds of fish that play an important role in the nutrition of the population. These fish are classed as small indigenous species although not all fish within this classification are particularly small.
Of the 260 species of freshwater fish found locally, over 140 species are classified as Small Indigenous Species (SIS) and account for over 80% of the total catch, consumed by the poorer section, as preferred species.
Common fish within the small indigenous species category include:
- Small catfish, Knifefishes, Snakeheads, Needlefishes, Minnows, Rasboras, and bards, Loaches,
Anchovies and sardines, Spiny eels, Climbing perch, Gobies, Mud Perches, Glassfishes, Freshwater prawns
C. Feeding the Fish
With the non-intensive approach, it is possible to feed fish on nothing more than scraps and waste, duckweed, oil cake, kitchen waste, rice bran and snails which will provide all the nutrition required.
Some low-cost feeds are brought in by the households, typically rice bran and oilcake, but these costs are minimal. Occasionally, the diet may be supplemented with commercially available compound feeds. In most cases, a mixture of diets is offered, according to their availability and needs of the fish.
FISH HARVESTING and MARKETING
Growth is rapid in the warm climate and the fish attain marketable size within 3-9 months, providing farmers with a rapid return on their investment and labor.
Fingerling production culture cycle is between 1 and 2 months. Cage nursery producers can sell fingerlings to the pond farmers and ox-bow lake operators.
Fish for food culture cycle is between 4 and 6 months. Fish food producers consume the caged fish as well as selling them in the market.
Profitability depends on many factors including the type of water body and culture, cage construction materials, the choice of fish species, fingerling size and price, stocking density, feed price,
availability of protein-rich feed, culture duration, cage management, harvesting, and marketing.
Another concern relates to economies of scale. Almost all enterprises are subject to economies of scale, and cage culture is no exception. The labor of looking after one small cage is far greater per kilogram of product than that for looking after a large one. The cost of the cage per kilogram of production will also be higher for a small cage versus a large cage. However, co-operative use of labor can be used to realize economies of scale in relation to labor, and this is already done in many villages.
The third concern, related to the second, is a comparative advantage. A significant proportion of the fish is intended to be sold for cash rather than consumed by the farmer and his family. In the medium term, an important question is whether small-scale producers in villages are well placed to compete for “ either with larger commercial producers, or producers from elsewhere. If they are not, and if competition increases, then prices - and returns - will steadily decline. In practice, there is strong local demand for fish throughout the country, and small-scale producers are well placed to serve widely-dispersed rural markets.
Secondly, the use of surplus off-season and/or family labor is itself a comparative advantage. Thirdly, in those systems which use local food resources, such as natural foods and kitchen wastes, feed costs are relatively low compared with those for commercial producers. Small-scale fish producers should, therefore, be able to survive competition in much the same way as village-scale poultry producers have survived, and even to some extent benefit from the increasing number of intensive poultry operations.
For more information, contact:
Bureau of Fisheries and Aquatic Resources
Dept. of Agriculture
PCA Building, Elliptical Road
Diliman, Quezon City
Tel. Nos. (632) 929-8074 / 929-9597
Email :bfarnmfd@info.com.ph
Web: ww.bfar.gov.ph
source: The original article appeared in www.practicalaction.org
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