Silver arowana

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Osteoglossum bicirrhosum

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Osteoglossiformes
Family: Osteoglossidae
Subfamily: Osteoglossinae
Genus: Osteoglossum
Species: O. bicirrhosum
Binomial name
Osteoglossum bicirrhosum
Cuvier (ex Vandelli), 1829

The silver arowana, Osteoglossum bicirrhosum, sometimes spelled arawana, is a freshwater bony fish of the family Osteoglossidae, commonly kept in aquaria. The term "Osteoglossum" means "bone-tongued" and "bicirrhosum" means "two barbels" (from the Greek language).

Contents

[edit] Description

This species is found in is the Amazon River basin and in the Rupununi and Oyapock Rivers in South America as well as in still waters in Guyana.

This fish has relatively large scales, a long body, and a tapered tail, with the dorsal and anal fins extending all the way to the small caudal fin, with which they are nearly fused. It can grow to a maximum size of around 1 m (39 inches) in captivity. In the wild, it has been known to reach over 1.2 m (47 inches) in length. The juveniles are usually a dull silver color with black markings around the head and the tail. Once they reach about 15 cm (6 inches), the markings will disappear and they will start to obtain the silvery color that give them their common name.

The species is also called monkey fish because it of its ability to jump out of the water and capture its prey. It usually swims near the water surface waiting for potential prey. Although specimens have been found with the remains of birds, bats, and snakes in their stomachs, its main diet consist of crustaceans, insects, smaller fishes and other animals that float on the water surface, on which its draw-bridge-like mouth is exclusively adapted for feeding.

Arowanas are sometimes called Dragon Fish by aquarists because their shiny armor-like scales and double barbels are reminiscent of descriptions of dragons in Asian folklore.

[edit] Conservation status

The Silver Arowana is currently not listed on any CITES appendix [1] nor on the 2004 IUCN Red List.[2] It is one of the most popular ornamental fish from South America, however, and therefore its conservation status merits attention.[3]

As reported by Environment News Service in August 2005, shared use of the Silver Arowana population was a cause for a dispute between Brazilian and Colombian authorities. Juvenile Silver Arowanas are caught in Columbia for sale as aquarium fish, while the people of Brazilian Amazonia catch adult fish for food. A sharp drop in the number of arowanas had caused Brazilian authorities to prohibit fishing of them between September 1 and November 15; the Colombians, on their part, would prohibit capturing them between November 1 and March 15. [4]

The Silver Arowana is often kept as a pet, being considered an accessible substitute for the Asian arowana, which is listed on CITES Appendix I and is therefore difficult and expensive to obtain legally.

[edit] Keeping Silver Arowanas as aquarium fish

Silver arowanas are primarily surface dwellers.
Silver arowanas are primarily surface dwellers.

[edit] Aquarium

To keep one of these large fishes, a properly sized aquarium is important. The minimum recommendable tank size for one adult Silver Arowana is 200 cm (72 inches) x 66 cm (24 inches) x 66 cm (24 inches), or approximately 180 gallons. A young specimen can be kept in a smaller tank, but as it grows a larger tank will be necessary to prevent deformities and to ensure the maximum length and life span of the animal.

Any aquarium housing an arowana should be tightly covered because of these fishes' jumping behavior.

[edit] Water Conditions

Water conditions are important for arowanas. Strong filtration is necessary for these large carnivores. Commercially available black water additives can help simulate the Silver Arowana's natural habitat, although they can adapt to most water supplies and thrive. A 25-30% water change, siphoning waste and other detritus, is necessary 1-2 times every week to maintain excellent water conditions. The water temperature should range from 24°C (75°F) to 28°C (82°F), with the ideal about 26°C (79°F).

[edit] Feeding

Young Silver Arowanas should not be overfed, because according to some hobbyists, they can develop dropeye, a condition in which the eyes are turned downward, as they grow. Arowanas should be offered meaty foods such as insects, shrimp, fish, beef heart, frogs, pellets, etc. Many aquarists recommend against live feeder fish because these are often raised in poor conditions and are capable of transmitting diseases to predatory fish; additionally, an arowana may eventually refuse to eat anything else but feeder fish which could prove to be very expensive. Mealworm exoskeletons are sometimes difficult for young arowanas to digest, so they are best avoided.

[edit] Tankmates

Silver Arowanas can be kept with other freshwater fish as long as they are too large to fit in the arowana's mouth and can tolerate the arowanas active-swimming lifestyle. Many people like having more than one Arowana in the tank; in this case, hobbyists recommend keeping at least 5 to 6 in the tank at a time because Silver Arowanas are very aggressive towards each other.

[edit] References

  1. ^ CITES Appendices
  2. ^ IUCN Red List
  3. ^ International meeting on ornamental fish boosts regional conservation and sustainable resource management initiatives (WWF)
  4. ^ Brazil, Colombia at Odds Over Silver Amazon Fish. A meeting between the representatives of the Amazon Basin countries in August 2005 was meant to discuss the dispute.


[edit] See also

[edit] References

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