A fish breeder from the Czech Republic has produced a new variety of selectively-bred Cardinal tetra which is gold and red in colour.
Dr Karel Zahradka of Prague, who is an occassional contributor to Practical Fishkeeping magazine and an expert tropical fish breeder, was given one of the golden morphs of the Cardinal tetra, Paracheirodon axelrodi, in a brood of fish spawned by a friend.
He has since managed to fix the strain so its offspring are predominantly the same as the parents.
The new Gold cardinal strain is erythristic and has the same bold red longitudinal stripe on the ventral surface but has a much paler silver-blue stripe and a more golden back than the wild-type fish.
Zahradka told Practical Fishkeeping: "The fry are a bit more sensitive and slow-growing than normal Cardinal tetras, but they are not very difficult to breed under the same conditions as Cardinals. One of my friends has now produced more than a thousand of them."
Some of the Gold cardinals have already been exported to the Japan aquarium trade and Zahradka expects the fish to also be exported for the European market soon.
Importers in the UK wishing to obtain the new Cardinal tetra should contact Dr Karel Zahradka at [email protected].
Natural morphs in natureBreeders have already been successful in producing new strains of the Neon tetra, Paracheirodon innesi, which is now available in a "diamond" form which has metallic scales on the dorsal surface, as well as a less common long-finned form.
Research by Paulo Petry of Bio Amazonia Conservation International and Phillip Harris of the University of Alabama has shown that the Cardinal tetra exists in several different natural colour forms in the Amazon basin, some of which could later be described as distinct species.
This fish may be the first selectively-bred form of the Cardinal to reach the aquarium trade. However, the Cardinal tetra exists as a number of phenotypes in the wild, including in the Rio Negro a gold form in which the blue stripe is replaced by yellow and a "silvery blonde" form where the entire dorsal surface and blue stripe is pale silver-blue in colour. "The Cardinal tetra exists as a number of phenotypes in the wild, including a gold form which is found in the Rio Negro..."The phenotype found in the Rio Negro has a metallic blue stripe reaching the adipose fin (see below image), while the form found in the Rio Orinoco drainage has a metallic blue stripe which stops between the dorsal and the posterior end of the adipose.
Cardinals were once considered a difficult species to breed, but many breeders are now producing the fish. The Czech Republic is one of the world's largest producers of Cardinal tetras and the bulk of the Cardinals sold in UK shops are now imported from breeders there the EU than exported from the wild.
Some Brazilian ichthyologists believe that fishkeepers should continue to support the sustainable Cardinal fishery of the Amazon basin, since thousands of people are employed in the region to source fish for the aquarium trade. The fear is that if the fishermen didn't catch Cardinals, they could turn their attentions to deforestation. In nature, the Cardinal is an annual species and does not appear to be dramatically affected by commercial fishing pressures.
Further reading: Harris P and P Petry (2001) - Preliminary report on the genetic population structure and phylogeography of the Cardinal tetra, Paracheirodon innesi in the Rio Negro basin. In Conservation and Management of Ornamental Fish Resources of the Rio Negro basin, Amazonia, Brazil. Project Piaba. ISBN: 85-7401-083-9.
Fact File: Cardinal tetra
Common name: Cardinal tetra
Scientific name: Paracheirodon axelrodi
Synonyms: Cheirodon axelrodi and Hyphessobrycon cardinalis are both invalid.
Origin: Blackwater rivers and streams in Brazil, Colombia, Guyana and Venezuela.
Size: 5cm/2" is a good size in the aquarium. Few wild fish reach this size as the species largely annual.
Water: Cardinals are found in very peaty blackwater regions where the water conditions can be very extreme. A pH of 3.0-4.0 is not unusual with negligible hardness. In the aquarium, wild fish generally do best in soft, acidic water. Aquarium bred fish can usually be acclimatised to harder water.
Aquarium: Cardinal tetras are best kept in a very large group (10+) in a blackwater biotope tank. They mix well with other fish from the region, providing they are not too large.
Availability: South American wild caught fish tend to be trickiest to keep, and usually demand soft water. Czech fish tend to be more expensive, but also a little more robust and simpler to keep.
Price: Around 1.50-2.00 each.