Yellow peacock bass, yellow tucunare

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Onglets

Description

Distinguishing features

While not at all related, yellow peacock bass resemble smallmouth bass, with the addition of three black vertical lines on each side of the body and a black spot at the base of the tail. Like smallmouth bass, they have two fused dorsal fins, the first with hard rays (spiny dorsal fin) and the second with soft rays (soft dorsal fin).

The genus Cichla contains 15 species known as peacock bass (or tucunare). Among these yellow peacock bass is considered a small species, even though it can grow up to 45 cm in length.

Reproduction

For reproduction, yellow peacock bass couples build two to four nests out of small rocks on the riverbed, but the female does not lay her eggs directly inside. Instead she will lay between 5,000 and 7,000 eggs (2.4 mm in diameter) on a solid substrate nearby. When the eggs hatch, the parents use their mouths to move the young to the nests.

The parents protect the eggs and then the fry, for two months, until they are 3.5 cm long. The female stays close to the nests while the male patrols the area a short distance away, chasing off any intruders who come too close. The parents barely eat during this period.

When the parents stop protecting their young, the fry form small groups that seek shelter in the dense vegetation near the riverbank.

Diet

A piscivorous (fish-eating) species, peacock bass are voracious predators at the higher levels of the food chain. They are very active hunters that relentlessly pursue their prey. They are so voracious that when introduced into a body of water for sport fishing, they can easily become a threat to local species.

Predators

As the yellow peacock bass is a rather large fish (up to 45 cm) it has very few natural predators, once adulthood is reached, except perhaps the giant river otter (Ptenoura brasiliensis), the boto or Amazon river dolphin(Inia geoffrensi), as well as caimans and humans.

Peacock bass (Cichla sp) are highly prized in the Amazon for sport fishing, especially the larger species like C. temensis, C. monoculus and C. ocellaris.

They are also eaten locally, due to their succulent meat. However, since peacock bass are at the top of their food chain, they contain high levels of mercury due to trophic magnification (explained below in the Ecology and Behaviour section). Consumption of this fish should therefore be limited.

Mercury is highly toxic for our body and can cause Minamata disease, which has many disabling symptoms, including tremors, weakness, loss of vision and difficulty speaking. Local health authorities recommend eating herbivorous species, like pacu, instead, since they contain lower levels of mercury.

Habitat

Yellow peacock bass is native to the clearwater rivers of the Tocantins River Basin and its tributary, the Araguaia River, in the Lower Amazon (Brazilian states of Pará and Tocantins).

Several tucunare species (but mostly yellow peacock bass) were introduced to southeastern Brazil for sport fishing. This practice harmed native fish populations, given the peacock bass’ predatory nature . Luckily, the famous Cichla temensis so prized by sport fishers has not managed to adapt well outside the blackwater of the Amazon (Rio Negro, Orinoco River, etc.)

Yellow peacock bass live near the banks of rivers, among vegetation, branches and other submerged objects, where they find refuge. During the rainy season, they inhabit clearwater flooded forests called igapós.

Ecology, behaviour

Peacock bass are rather sedentary. They can migrate when prey becomes scarce, but will not venture more than 40 kilometres away.

They also tend to be very territorial, especially when defending their nests and young. They will not allow any other fish to approach.

During the 80s, a team of Canadian and Brazilian researchers (which included Robert Davidson, a researcher from the Montréal Biodôme), discovered a connection between the deforestation of the Amazon rainforest and mercury contamination of the rivers. They discovered that clearcutting of forests releases mercury, which has accumulated naturally in the soil over thousands of years. This mercury is then transported by rainwater and once it enters a waterbody it is incorporated into the food chain as methylmercury.

Piscivorous species like peacock bass accumulate the highest levels of mercury. This process is known as trophic magnification. Here’s how it works:

Methyl mercury is first absorbed by aquatic plants. Since it is difficult for an organism to eliminate this substance, herbivores absorb the mercury that has accumulated in the plants. The carnivores that feed on these herbivores accumulate the mercury contained in their prey. Carnivores further up the food chain, like peacock bass, feed on these small carnivores and thus contain the highest levels of mercury.

French name

Tucunaré jaune

Scientific name

Cichla kelberi

Phylum

Chordata

Class

Osteichthyes (bony fish)

Order

Perciformes

Family

Cichlidae

Size

Up to 45 cm long

Weight

Up to 1.5 kg

Life span

Estimated at between 10 and 15 years

Status

Least concern (IUCN 2017)

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