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Monday, June 7, 2010

So You Want To Breed Arowana?

The Golden Arowana is the most popular and expensive ornamental fish. The best quality is the crossed-back full scale Arowana is the Golden Arowana. In its natural habitat breeding season normally occurs from August to October every year. In its natural habitat the fish prefer slightly acidic clean water and unpolluted natural surroundings, especially shallow and fast flowing rivers with overhanging vegetation on the river bank. 

Rear eight Arowanas in a bare-based concrete tank measuring 5 x 5 meters with a water depth about 0.5 meters fenced with plastic netting about 0.75 meters high to prevent the fish from jumping out. A spawning room was built in one corner of the concrete tank and some pieces of bogwood were added to help create a natural living environment for the fish. Other decorations such as pebbles and stones were avoided because they may injure the fish and be swallowed accidentally during feeding. The rearing tank was partially shaded, away from direct sunlight and built in a quiet area. The broodstock were maintained in the rearing tank until the fish reached maturity. 

 Although arowana is a hardy fish the quality of water should correspond to the pH of water in its natural habitat when reared in concrete tanks. The pH of water in the rearing tank should be maintained between 6.8 - 7.5 and 27 - 29°C. Water was partially changed at about 30 - 35% of total volume and topped up with dechlorinated tap water. The water depth was maintained at about 0.5 - 0.75 meters.

Broodstock should be fed a variety of food. A balanced diet is very important in helping fish to mature and spawn. The daily diet should be diverse and contain a high protein content. Feed them daily with meat-based live food such as wild guppy, freshwater prawn (Macrobrachium lanchestrii), low grade goldfish and chopped fish meat. Pellet feed containing 32% crude protein was also given as supplementary food. Total amount of food provided was approximately 2% of total body weight per day. 

The fish should attain first maturity from around the 4th year onwards at which point they measure between 45-60cm in total length. The fish spawn throughout the year with the peak season occurring between July and December. In the wild the male incubates the fertilized eggs in its mouth cavity until the fry are free swimming after about 2 months. 

The arowana shows very unique behavior during courtship. Courtship takes place from several weeks to months before the pair starts to mate. The courtship sequences usually are observed at night when the fish tend to swim closer to the water surface. The male chases the female around the perimeter of the tank and sometimes the pair circle each other nose-to-tail. About one to two weeks before spawning takes place, the fish swim side by side with their bodies touching. Eventually the female releases a cluster of orange-red eggs.
The male fertilizes the eggs and then scoops them into its mouth where it incubates them until the fry can swim and survive independently. The eggs are about 8 -10 mm in diameter and rich with yolk and hatch about one week after fertilization. After hatching, the young larvae continue to live in the male's mouth for a further 7 - 8 weeks until the yolk sac is totally absorbed. The fry leave the mouth and become independent when they reach about 4550mm. 

After mating a brooding male can be identified by a distended operculum and its swimming behavior. They don't seem to feed and look more placid than at other times. A brooding male can also be recognized by a remarkable brood pouch located at the underside of its mouth. The incubation period (time from fertilization until the fry are released) is normally about 8 weeks. To shorten the period the fertilized eggs can be hand removed from the male's mouth on the 30th day after spawning. The brooding male should be carefully caught with a fine net and covered with a wet cotton towel to avoid injury and struggling. 

The lower jaw of the fish is pulled backward slowly and the body is shaken slightly to release the half developed larvae from the male's mouth. The larvae are collected in a plastic basin and incubated in an aquarium. The number of the fertilized eggs collected in a single brood is usually about 20 - 35 larvae.

Once removed from the male's mouth, the half-developed larvae are incubated in glass aquarium tanks, measuring 90 x 45 x 45 cm. Water temperature is kept around 27 - 29°C using a thermostat heater and dissolved oxygen is maintained at about 5 ppm (mg/l) through continuous gentle aeration of the water. Add about 2 ppm of Acriflavine solution to the water to prevent infection of any injuries suffered by the larvae during handling. Using this in vitro hatching technique, the survival rate to free swimming stage is generally about 90 - 100%. 

During the first few weeks when the larvae still have a large yolk sac, they tend to remain at the bottom of the tank most of the time. The fry start to swim upward periodically when the yolk sac becomes smaller. On the 8th week the yolk sac is nearly fully absorbed and the fry start to swim horizontally. At this stage the first live food should be given to the fry. The yolk sac is fully absorbed and the fry become free- swimming at about 8.5cm in length. 

During the incubation period the fry do not need to be fed. The fry will swim freely on the 7th week. Supplementary external live feed such as young guppys or bloodworm can be given at the early free-swimming stage to prevent the fry from attacking each other. The fry are very vigorous feeders and should be provided with ample supply of feed. We recommend a partial water change of about 30% of total tank volume every 2- 3 days to maintain water quality. 

Bigger fry of about 10 -12cm in length can be fed with freshwater prawn or chopped fish meat to accelerate their growth rate. At 4 months in age, rear fingerlings individually in 75 x 45 x 45cm aquariums to avoid physical defects from fighting with siblings. Illuminates with artificial lighting at least 10 -12 hours a day to enhance the colour and promote the formation of chromatophores.  After 6 -7 months of free-swimming the fry measure about 20 -25cm in length are suitable for market. 

Breeding of arowana in earthen ponds is commonly practised by commercial ornamental fish farms. To start the business the breeding operation needs a large amount of money for the cost of capital such as buying the broodstock and building new infrastructures.




3 comments:

  1. Very cool looks like a decoration in the aquarium, always loved gold:)) It is necessary to try to do it at home.

    ReplyDelete

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