To meet the demand for tilapia fingerlings, more private hatcheries should be established. Although some fish-farmers specialize in fingerling production, many of them are engaged in fingerling and food fish production simultaneously. As the indury expands, farmers realize the importance of using good quality fingerlings. As long as the demand for fingerlings exists, a well-managed hatchery is a lucrative business.
BROOD STOCK SELECTION
Genetic improvement of tilapia is imperative to the development of the industry. Select quality brood stock to improve tilapia production. Choose pure quality stocks and do not allow them to crossbreed with other species to preserve their genetic quality. Tilapia farmers should buy their stocks only from reliable and established sources.
Maintenance of Good Quality Stock
It is necessary to maintain high quality pure stock with the following measures:
- Prevent the introduction of inferior tilapia species into the brood ponds. Filter all incoming water or use ground water, if possible
- Use brood fish of about 100 g or more. If larger brood stock are used the original stock can be easily identified after each production cycle. Use the same stock repeatedly, depending on their performance.
- Adopt an independent culling-selection process for undesirable stock. Always eliminate fish that has questionable characteristics
- Examine breeders carefully when re-stocking after each cycle.
- Avoid introduction of breeders from non-accredited sources.
- Teach laborers and caretakers the importance of preventing genetic contamination.
- Drain ponds completely and remove all stocks pond reconditioning.
The open pond is the simplest and most common method of fingerling production. In this method, a pond serves both for spawning and rearing. Stock breeders into the ponds and allow to spawn naturally at controlled conditions.
Brood fish stocking rate. Stock pond at the rate at 100 to 200 kg brood stock per hectare at a sex ratio of 1:3 or 1:4 male to female. Brood only fish weighing about 50-100 g. A female brood fish of 90-300 g produces as much as 500 eggs per spawning. However, brood fish may be used continuously for a period of 3-5 years. Use larger breeders to identify them as brood stock.
Collecting, grading and conditioning fingerlings. Collect fingerlings 30-45 days after stocking of breeders using knot 32 mesh seine. Do this 3-4 times per harvest period at an interval of two to four weeks.
Grade collected fingerlings by using 22k, 17k, 14k and 10k nets. Release breeders back to the pond immediately. Condition collected fingerlings by stocking these in "hapa" or tanks for 3 or more days before disposal. Give the fingerlings supplementary feeds at the rate of 3% body weight. However, stop feeding 24 hours prior to disposal. The ideal stocking rate for 'hapa" is 2-3 kg of fingerlings per cubic meter.
The average number of fingerlings harvested should be at least 100,000 pieces per hectare per month or about 1.2 million per hectare per year. Increasing the frequency of harvesting and minimize predation and cannibalism by the parent fish and other predators of the fingerlings.
Recondition the ponds after 120 days or sooner to increase production.
Restock small fingerlings in earth nurseries to reach the desired size of size 22 at 15-30 days and size 17 at 45 days. Stocking rates between 25 to 30 fingerlings per square meter give optimum results.
Routine hatchery pond fertilization. Aside from the basal fertilization, apply organic fertilizer uniformly such as air-dried chicken dung at the rate of 750 kg/ha per week or 3 tons/ha per month.
Apply inorganic fertilizers (16-20-0) at the rate of 100 kg/ha per month. New ponds may require higher rates of fertilizers.
Increase the rate of fertilizer if plankton bloom does not appear within 5-10 days. Apply fertilizer by means of the platform or by the hanging sack method.
Feeding. If manure is not applied, use supplemental feeding feed fish with rice bran at the rate of 2-3% of their body weight per day. Give 1/2 of the daily ration in the morning and the other half in the afternoon. Drain the pond completely after 90-120 days to eliminate predators and prevent inbreeding. To prepare the pond for the next production cycle, refer to "Fishpond Preparation".
- management is very simple, but effective
- the pond serves as spawning and rearing pond, thus, the fingerlings produced are larger compared to those produced through the other methods
- no supplemental feeding is required at high manuring rates
Disadvantages of the Open Pond
- the number of fingerlings produced per square meter is lesser compared with the other methods
- the fingerlings produced are not of the same size; they need to be graded upon harvesting.
"Hapa" Method
A "hapa" (net enclosure or "bitinan") is like an inverted mosquito net which the four top corners are tied to bamboo stakes. It is made of fine meshed polyethelene netting. The seams are sewn with nylon thread and double stitched to prevent splitting.
A "hapa", measuring 3 m long , 3 m wide and 1.5 m deep is the most common size used. Usualy, it is installed in ponds, lakes or along river banks with slow moving current. The open part of the "hapa" should be two feet above the water surface.
Advantages of the "Hapa" Method
- production on a per square meter basis is high
- fry are more uniform in size
- fry and breeders are easily handled
Disadvantages of the "Hapa" Method
- management is more complicated and intense compared with the other methods
- brood fish in "hapa" are easy targets of poachers
- "Hapas" may be destroyed or blown away during typhoon or stormy weather
- feeding of breeders and fry is a must
Stocking. In the "hapa" method, the sex ratio of male to female is 1:5 to 1:7. Stock 4-5 breeders weighing 50 to 200 g pe sq m.
Feeding. Feeding is a must in the "hapa" daily for the presence of schooling fry. Two weeks stocking of breeders, scoop out fry and transfer these to tanks, other "hapas" or rearing pond. Feed collected fry a diet in powdered form at the rate of 5 percent of the total body weight.
Collecting fry. Check the "hapa" daily for the presence of schooling fry. Two weeks after stocking of breeders, scoop out fry and transfer these to tanks, other "hapas" or rearing ponds. Feed collected fry a diet in powdered form at the rate of 5 percent of their body weight per day. Feed four times a day until they reach the desired size.
HANDLING AND TRANSPORTATION OF FINGERLINGS
Transporting live fish involves hauling of a large number of fish into a small quantity of water. Unless this is done properly, water quality deteriorates causing fish mortality. The use of plastic and buri bag or hauling box with aerators are new methods commonly used in transporting live fish. The objective of having a good transport system for live fish is to minimize stress on the fish and ensure a high rate of survival.
Conditioning Fish-prior to Transportation
Place fingerlings havested from brood ponds or nurseries in "hapa" or aerated concrete tanks at least three days prior to disposal. This process is called "conditioning". It allows the fish to recover from handling stress at harvest time. Feed fingerlings during conditioning, but stop feeding 24 hours prior to disposal.
If the fish are held in tanks, supply these with sufficient aeration. Tanks used for holding fish should be clean, leak-proof, and glazed or painted with epoxy paint to discard rough surfaces. Smooth surfaces reduce physical injuries to fish. One cubic meter of water in tanks can hold approximately 4.4 kg of fish.
Avoid overcrowding in holding "hapas" or tanks especially in the early morning when dissolved oxygen level is low. If fish go near the surface gasping for air, increase aeration or decrease the holding rate. Well-aerated water could hold more fish.
Method of Transporting Live Fingerlings
a. Plastic bag method
The most common size of plastic bags which can hold large quantity is 20 inches x 30 inches x .003 gauze double seine. Use standard sized "bilid-bilid" "bayong", or pandan bags to support the plastic bags. Transport 400 pieces of fingerlings of size 22 for a duration of 24 hours for long distances and for short distances 800 to 1,000 pieces of the same size for not more than 6 hours.
Maintain the temperature at 28°C to 30°C while transporting. To reduce fish mortality and stress during the trip, place about 500 g of cracked ice between the two plastic bags (figure 8). This technique increases survival rate of fingerlings.
Pointers in using plastic bags
- a set consists of one pandan bag and two plastic bags.
- check the plastic bags carefully for holes, put one bag inside the other
- fill the plstic bag with eight liters of clean water
- water temperature in the holding "hapa" or tanks should be the same as that of the bag
- load the fish in the bag. For small deliveries, count fish individually. For big deliveries, use the average weight or volumetric method
- use the recommended loading capacity to reduce mortality
- fill the bag with 1.5 L of medical oxygen immediately after it is filled with fish
- tie the oxygenated bag with rubber immediately to avoid oxygen leakage
- icing is advisable when transporting fish for more than six hours and if water temperature is 30°C.
b. Hauling box or tank method
Construct the haulin tank or box out of fiber glass, alumimum sheet, marine plywood, metal sheet, or stainless steel. Construct this such that it can hold water. Provide a cover to prevent water from splashing. The cover should be provided with hinges to make it fold. Put holes exactly the size of the agitator. Paint boxes of marine plywood with epoxy paint to make these durable. The most common size of hauling boxes made of marine plywood is 3 feet long x 2 feet wide x 2 feet deep.
An agitator is basically mechanical stirring blade. It is covered with a screen to keep the fish from being hurt. The blade extends partially into the water and its rotation produce air bubbles. Connect this to a 12-volt battery of the delivery vehicle or provide extra battery for that purpose.
The capacity of the hauling box is approximately 0.18 to 0.24 kg of fish (irrespective of size) per liter of water 50-60 kg per 270 liter box.
Loading Techniques
Before loading the fish in the hauling box or tank, know the total weight of the fish. Do this by getting their average weight using the following formula:
Average weight = Total weight of the fish sampled in kg / total # of fish sampled
Example:
Total weight of fish sampled: 1,000 g or 1 kg
Total number of fish sampled: 1,000
Average weight of fish: 1/1,000 = 0.001 kg or 1 gram
Number of fingerlings to be loaded = Capacity of hauling box / Average weight of fish
Example: 50 kg/001 kg = 50,000
Fill the hauling boxes with water to about one-half of the agitator's shafts and run the agitators for 3 min. before loading the fish to provide oxygen while loading.
Water temperature of the hauling box should not vary more than 5°C from that of the holding water. Handle fish carefully to prevent shock and stress.
Unloading Techniques
Abrupt changes in temperature cause thermal shock to the fish. Check water temperature before releasing the fish into the stocking pond to prevent thermal shock and stress.
Source: http://www.da.gov.ph/tips/tilapia/fingerlings.html
Posts
0 comments
Post a Comment