Jonny recently bred Asian arowana, also known as dragonfish â€” a first in Europe. He is assistant curator at Bristol Zoo Aquarium.
How old were the parents?
We acquired them from a Customs seizure in 1996. They were wild and we don’t know how old they were. We’ve had them 13 years now.
What triggered the spawning?
Probably because we kept four adults in a large system and had a lot of luck! They had been showing spawning behaviour for a few years, including nipping fins and ‘dancing.’ About a year before the fry came we switched to RO which softened the water. We then upped the temperature to 28ËšC/82°F and installed a large spraybar to simulate rainfall. Shortly after they began to spawn.
How long did they brood the fry?
About eight weeks before the fry hatched we noticed the brood pouch was distended. We took 16 fry from the adult’s mouth and left 10-15. We held off as long as we dare before stripping the fry. We timed it just right as the fry had fully absorbed their yolk sacs and were fighting fit. Prior to this the same adult had kept a clutch for five weeks but they were found on the aquarium floor by week six.
What parental care did they show?
The brooding adult became very subdued during during the eight weeks and formed a strange bond with our Giant gourami. The dragonfish would sit in a corner away from the others and if any came over to nip his fins the Giant gourami would see them off!
This happened repeatedly, right until the fry were released. Other than that we never saw fry emerge from the mouth. We only saw tiny eyes looking back at us when the adult swam past. He didn’t feed for the duration and lost quite a lot of weight. I am pleased to say that he’s fighting fit again now and has been spawning again. The fry we left in the mouth of the adult arowana did not survive.
How do you feed the offspring?
We started off feeding the fry on gut-loaded crickets, which they took from day one. They have grown a lot now and are all eating mussel, cockle, bits of trout and invertebrates. Some went off their food for a while so had to be encouraged to feed — but now we need to watch our fingers!
What size tank do you keep them in?
The adults are in a 20,000 l/4,400 gal tank (6 x 2 x 2m/18’ x 6’6” x 6’6”). The juveniles are in two 150 l/33 gal tanks. We had to split them as they became very competitive for food. They will shortly be moved on to larger tanks.
This article was first published in the September 2009 issue of Practical Fishkeeping magazine. It may not be reproduced without written permission.