The rock bacu

(Lithodoras dorsalis = skin of stone)

The spectacular Rock bacu or as known here on the Amazon river of Peru, Cahuara(ka-wara) ladrillo (brick)have a very interesting natural history. They have evolved quite an important niche in seed dispersal of plant species especially palms of the seasonally flooded forests of the Amazon river basin
20121221-113227 a.m..jpg .
This peculiar catfish was known to modern ichthyology only through dried specimens less than 30 years ago yet It turns out that locals have been eating them for thousands of years. River dwellers were catching them in weir traps that close off sections of flooded forest where they primarily feed almost half the year. For some time, people have been catching them with hook and line in the Oran region of the Amazon River

The bacu feeds heavily on seeds and fruits of the seasonally flooded forests throughout the Amazon basin. This fish among other catfish are important seed dispersers of palms and other fruiting trees of the flooded forest.

20121221-012340 p.m..jpgMost palm seeds are heavy and sink. They would not float off with a slight current and get trapped close to the trunk, settling into the thick leaf litter. This would cause an overcrowding of seedlings close to the mother trunk.

These fish are wired to respond to the sound of fruits falling, and they instinctively investigate and consume any seeds they can find. The bacu can also sense fruits by “smelling the water” .

Certain trees have specific smells either due to the rotting fruit or the tree trunk and roots itself. Fish that depend on flooded forest fruits can sniff out where their next meal may be.

After consuming whatever is available in an area, they swim off to defecate them in away from their origin. This way the next generation will have a better opportunity to grow. Whole mature stands of palms that are in lowland areas can be the products of bacu seed dispersal.

These catfish do not destroy the seed that they feed on. Many seeds have a soft mesocarp that is ground off inside their stomach or mouth and the whole seed is passed. Other destructive fish actually destroy the shells of some seeds, helping dispersal but also consuming seeds that would be new plants.

To learn a bit more about fish and seed dispersal check out this paper on ichthyochory

In the season of falling water levels, the majority of these fish will migrate into the main river channels as the igapo forests dry out. In this period they are omnivorous eating fish or aquatic vegetation as the fruits are no longer available. It is unclear where and in what season these fish breed. It is believed that these bacu fish spawn annually in the estuary region due to the tremendous amount of juveniles located close to the mouth of the Amazon in semi brackish water

Can you imagine that this catfish has survived millions of years evolving with the forest that surrounds its aquatic domain? They are one of the strangest armored catfish that exists. Their ventral scales have practically no symmetry! Take a look the pictures here and see if you can find the pattern. I certainly cannot.

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This particular specimen weighed in at 16k. and was caught with live bait, rod and reel close to Otorongo Expeditions jungle lodge on the main channel of the Amazon River. I will not divulge the secret of how to catch, if you would like more information on trips to catch river fish like these Contact Anthony at

20121221-100802 a.m..jpgThere is no match for any other fish in Amazonia when considering tough armor and spines. This bacu is one of the largest of the thorny armored catfishes that can reach up to and most likely exceed 20k and lengths of over 100cm.

As usual it is necessary for me to note that the flooded forests are the first ecosystems to be degraded by human activity, mostly by clear cutting for pasture, agriculture or other reasons. Many seasonally aquatic ecosystems have been disrupted before they can be completely understood.

For a long time the lumber and oil companies through the government maintained a common idea to the public that the Amazon River and its forests has a homogeneous makeup throughout it’s entire realm.

This view is completely incorrect and only serves the companies so they may keep exploiting unfettered by the public worrying.

If fact the Amazon Basin has proved to be a diverse heterogenous mix of forest stands and river types that reveal secrets to the scientific community every day. As stated above , some areas especially in the Brazilian Amazon region, hundreds of kilometers square of seasonally inundated forest have been irreversibly changed to meet human demands.

Who suffers? In the long run, everyone

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