Silver arowana

Order: Osteoglossiformes

family: Osteoglossidae

Osteoglossum bicirrhosum (Cuvier, 1829)

This fish is found in the fresh waters of South America, specifically in the Amazon, Essequibo and Oyapock basins. It inhabits both the white rivers (with waters rich in minerals) and the black rivers (with water with a very low pH and a high content of humic and fulvic acids). In the dry season it inhabits slowly moving or stationary tributaries, backwaters and lagoons, while in the wet season it moves to floodplains. Due to its predatory behavior, it prefers shallower waters. It is able to adapt to an environment with low levels of dissolved oxygen in water. They then use their swim bladder as an additional respiratory organ.

Appearance

Arowana reaches a length of 90 cm, although there are reports of individuals growing up to 1.2 m. The maximum documented weight was 6 kg. Its elongated body is covered with very large, decorated scales, the upturned muzzle is crowned with 2 spines, while the dorsal and anal fins extend practically from the middle of the fish’s length to the caudal fin. Coloration changes with the age of the fish. The juvenile body shows blue reflections and a yellow-orange stripe, while the adult specimen is silvery. A characteristic feature is its bony tongue, which is helpful in catching the victim. In addition, many parts of the mouth have teeth, including the jaw, palate, tongue and throat.

Feeding

It is an omnivorous fish that feeds at the surface of water. The position of its mouth allows it to grasp the prey from below. It has unique predatory behavior. It stays close to the shore and waits for the passing victim. Usually it is placed sideways next to a fallen tree, then it is less visible. During the attack on the prey, it can jump above the water surface. This particular behavior earned it the nickname “water monkey” or “monkey fish”. Despite the fact that its general diet includes insects, mollusks, crustaceans, smaller fish and other floating animals, the remains of birds, bats and mice have also been found in its stomach.

Reproduction

Arowana is a dioecious species with spawning at the beginning of the wet season, i.e. in December and January. During the entire breeding season, the female is able to produce 50-250 eggs, and the typical size of a single brood is 12-30. The role of the female is limited to laying eggs. The male takes care of the offspring, first it houses the eggs, and then the larvae and juveniles in its mouth. The fry are usually quite large and after hatching they are 50-75 mm long. The young stay in the male’s mouth until their yolk sac is absorbed, which is about 2 months. During this time, the fishermen catch the males, take out the juveniles and sell them. Young ones with a visible yolk sac are very often available on the market.

Economic importantance

The shared use of the silver arowana population of Brazil and Colombia was the cause of a dispute between the authorities in 2005. The Colombians recruited young arowanas for sale as aquarium fish, while the Brazilian Amazon caught the adult fish for food. This resulted in a sharp decline in the number of arowanas. Fishing bans were introduced in Brazil from 01/09. to 15/11, and in Colombia from 1.11. and 15.03. Arowana has great economic value for the local population. It is the largest source of protein compared to other Amazonian fish. Moreover, due to its low fat content, it is considered the most digestible and the least susceptible to disease. The Amazonians of Coboclo consider it the only acceptable food for women in the puerperium. Arowana is also of great value in the aquarium industry, as evidenced by its sale on many commercial websites and the prices it achieves. However, it is the cheapest of all arowana species. A specimen of the much rarer Asian arowana was sold for $ 300,000. The Osteoglossidae is the only freshwater fish family that lives on both sides of the Wallace Line, with four important species in South America, one in Africa, one in Southeast Asia, and two in Australia.

Can arowana survive in waters of Poland?

In 2016, a single representative of the silver arowana was observed in Lake Poniatowskie. This individual was 40 cm long and was in poor condition. It was injured, most likely from attacks by other fish. There is no chance that it would survive in Poland’s freshwater reservoirs due to the prevailing low temperatures.