Oscar

order: Perciformes
family: Cichlidae (cichlids)

Astronotus ocellatus

It is an endemic species of the Amazon basin. It lives in the water column in areas where the current of water is free and the ground is muddy or sandy. Juveniles prefer a bottom covered with vegetation, where they can hide from predators. This fish lives from 10 to 20 years and grows up to 40 cm long. It is omnivorous, it feeds on fruits, molluscs and other aquatic invertebrates, insects and fish, which it actively hunts for. It lives in small schools in an area of its territory which it defends. During reproduction, it forms monogamous pairs. After laying eggs, it protects the breeding area, and after larvae hatch, takes care of the offspring. It can quickly change its coloration, mainly in the case of territorial fights. Its body, in place of its natural olive-green-brown color, becomes black with irregular white streaks. Juveniles differ in color from the mature ones, their body is covered with white and orange wavy stripes, and the heads are speckled.

This cichlid is extremely resistant to oxygen deficiencies that may occur in its natural environment, mainly in the seasonally flooded jungle, where it searches for food and breeds.

Mature individuals are more resistant to lack of oxygen than juveniles and can withstand up to 6 hours in completely anaerobic conditions. They can survive for 20 to 50 hours in low oxygenated water (5-20%). Due to their coloration, they have gained great popularity as an aquarium fish. Many varieties of color and shapes were bred. In the Amazon region they are used for consumption, their meat is very tasty.

How does the oscar defend against piranha attacks?

Piranhas of the genus Serrasalmus or Pristobrycon often feed on the fins of large fish. Fins provide them with an abundant, quickly renewable food source. It has been observed that the oscar is much less frequently attacked by piranhas than other fish of the same size. This is due to its coloration, specifically the artificial eye spot, which is located near the caudal and dorsal fins. It is a dark spot surrounded by an orange ring imitating the eye of a fish. In this way, the predator is confused and it is more difficult for him to locate the fins.