Arowana breeding and DNA


Arowana blogger
I just came across the following on AF; it is old information but likely of interest to some on the site (See: )

Discovery of arowanas' secrets boosts breeding

Molecular tools help uncover the breeding habits of expensive fish

by Shobana Kesava, The Straits Times Friday 3 Oct 08;

UNLIKE most of their scaly counterparts, Asian arowanas mate for life, local studies by ornamental fish farmers and scientists have found.

And when it comes to taking care of the brood, father knows best. The male carries the babies in its mouth for over six weeks before allowing them to swim free.

The secrets of the world's most expensive ornamental fish were uncovered using molecular tools at the Temasek Life Sciences Laboratory (TLL) and the fish of mainboard-listed Qian Hu, during a five-year research project.

Their discoveries on breeding habits have led to a doubling in fish production.

'In the second year alone, it was a 50 per cent increase and each year since then, its been a 20 to 30 per cent increase on the previous year's broods,' said lead researcher at TLL, Mr Alex Chang.

Qian Hu managing director Kenny Yap said the group produces a third, or about 10,000 of the world's supply of this freshwater fish each year.

The studies were conducted on close to 230 adult fish which had their genetic fingerprints put under the microscope.

'Knowing which fish have paired up could reduce breeding costs, because we can bring smaller numbers of fish together in a single small pond,' said Mr Yap. It can also guarantee customers who pay thousands of dollars for a fry complete information on the pedigree.

Traditional breeding methods have been hit-and-miss because farmers cannot tell one sex from another, let alone which fish have formed pairs. Breeding patterns are also hard to predict.

'Most are monogamous, with the odd few going astray or preferring complete celibacy, much like humans,' said Mr Yap.

To achieve the most prized characteristics and increase the baby count, the next phase of the research will use 'in-vitro' fertilisation. This will guarantee specific characteristics are carried by lineage.

'Within reason, we'll be able to give the buyers what they want - bigger fins, brighter colour, favoured shape of head,' Mr Yap said. The company is investing another $3 million over the next three years, on top of the initial sum of $1 million, to start a research centre in Sungei Tengah next year.

Mr Chang, Qian Hu's first formal scientific scholar, will head the facility, which will have 32 ponds. Two-thirds will be for breeding while a third will be for research.

Professor Peter Ng, director of the Tropical Marine Science Institute, said findings could change the conservation landscape for this species. 'Of the red, green and silver arowana in the wild, the red is most endangered. There is a chance it is a separate species and if this is proven through the genetic tests, more must be done to protect them.'

With Qian Hu's expected jump in arowana production, stocks in the wild could be replenished, said Mr Chang. - IMO red does overstock production from Indonesia last yr 2009.


Tracing the lineage and habits

* DNA tests comparing fossils and present day arowana show the popular red and green arowana diverged from their prehistoric predecessors up to 30,000 years ago, when Kalimantan separated from the rest of its South-east Asian landmass.

* The fish lack sexual dimorphism - they look the same whether male or female. They become fertile after three years and naturally spawn up to 80 marble-size eggs once a year. In-vitro fertilisation, using cryogenically frozen sperm and eggs harvested from the mother, could see many more fish produced.

* They remain fertile for about 30 years and generally mate for life.

* Extremely protective, the father carries the brood in his mouth for 45 days till they are large enough to fend for themselves. The male fish starve during this time.

* These top predators usually eat live amphibians, fish and insects. TLL and Qian Hu intend to optimise medicines and diet for these prized pets to increase their reproduction.

* A five-month old, 15cm-long red Asian arowana, the most prized colour, can fetch sellers $2,500. The largest known 40-year-old specimens reach 1m.


Go Forth and Spawn

Mother Nature gets a hand in efforts to boost the arowana fertility rate

Not many of us get to combine our passion with work, but Mr Alex Chang, a research fellow currently pursuing his PhD with Temasek Life Sciences Laboratory (TLL), gets to do that and more.

As the first recipient of the Qian Hu-TLL Life Sciences Scholarship, he is currently involved in research and development (R&D) work, which once fully commissioned, could revolutionise the way farmers breed arowana.

Launched in January 2004, the scholarship aims to train researchers for R&D that is highly relevant to the ornamental fish
industry, and in turn, move the industry towards becoming more knowledge-based.

The unique aspect about the project, said Mr Chang, is that it merges traditional aquaculture with modern molecular and
scientific tools. "Our approach uses high-end molecular tools to understand the breeding biology of the arowana, which is a big contrast to basic aquatic research which is restricted to conventional methods like selective breeding," he told Today.

Arowana, or dragon fish, is currently the most popular pet ornamental fish, due to its association with good feng shui, especially among businessmen. Covered in glistening gold, silver or red scales, the fish is regarded as a "good luck charm", bringing peace, harmony and prosperity to businessmen. In recent years, arowana hobbyists have almost tripled in number here, many of them keeping the freshwater fish for its unique beauty.

The Chinese call it the "dragon fish" because its elongated body, large mouth, eyes and barbels on the lower jaw resemble images of the mythical beast. While the fish can live up to 100 years, they fetch a high price of between $3,000 and $50,000, as they are difficult to breed, spawning well only in natural ponds. Of late, its appeal has spread further, with India and the United States seen as potential lucrative markets.

The $1.2-million research project, is a collaboration between Qian Hu and TLL, a non-profit organisation established in 2002 to undertake research in molecular biology and genetics. Qian Hu, a home-grown fish farm that was the first of its kind to seek a mainboard listing in the region, is also Singapore's leading exporter of ornamental fish.

"This is the first time in Singapore that a fish farm is working with a research institute and sponsoring a student for a PhD
programme at the same time," said Mr Chang, who has been working with arowanas for more than five years, and has authored a handbook on Asian Cichlasoma.

Qian Hu was keen on the project, as the results of the study will help remove two barriers that have persisted in traditional
methods of breeding: Understanding the mating behaviour of the arowana, and ultimately breeding higher quality fish.

For now, the arowana's breeding behaviour appears a little mysterious, as there are no conclusive studies to indicate if they are strictly monogamous or polygamous in their choice of partners. The matter is further complicated by a lack of sexual dimorphism, that is, the male and the female look exactly the same. However, what is known is that it is the male arowana that picks up the eggs after fertilisation and incubates them in the mouth for about two months before the fry are released to survive on their own.

"The traditional method of breeding is to place about 20 arowanas in the pond, and after two months, harvest the fish and check to see if there are any eggs in the mouth," said Mr Chang.

A lot of care is taken not to injure the costly fish, making the process labour- and time-consuming. "This is how the industry has been operating for the past 15 years. Even if you find a male with the eggs in his mouth, no light is shed on how many males or females there are in the pond or who the mother is."

By picking a small scale from the fish and extracting the DNA, microsatellite markers, which are DNA markers used intensively in forensic sciences, will show who the parents are. "DNA extracted from the fish will enable us to tell how many male and female arowanas there are in the pond. In addition, it also tells us which fish is mating with whom. In this way, we can separate the parents and put them in their own enclosure to breed in peace."

By separating the pair, it is hoped that the frequency of breeding will increase, as there is less competition from rival suitors. As the fish pass down their genes the Mendelian way, that is, one set of genes from the father and another set from the mother, the study will look into the possibility of pairing a "good-looking" arowana with another "good-looking" one so that the quality of the offspring is enhanced.

But even with increased production, Mr Chang does not believe that demand and price for the fish will drop because a lot of new markets have opened for the 20 or so registered farms here.

Aside from demand from China and Taiwan, there is also a resurgence seen from Japan, as it recovers from its economic slump.

The research will also help consolidate Singapore's position as a leader in the ornamental fish market. According to statistics from the Food and Agriculture Organization of the United Nations (FAO), Singapore currently exports about 30 per cent, or about US$50-million-worth ($78 million), of the world's ornamental fish export market. The global ornamental fish market is estimated to be around US$166 million.

"Competition in the arowana market is intensifying, with more Indonesian and Malaysian farms also looking into breeding the fish. If Qian Hu, as the only listed fish farm here, is not going to move one level up, then we will remain as just another arowana supplier in the market," Mr Chang emphasised.