Many knifefish fans soon discover they own a big fish. New contributor Alex Bell introduces a handy ‘pocket sized’ version that much easier to manage.
NEW SPECIES of fish are constantly being discovered, with around 200 species being described in 2021 alone. Many of these were found in areas of the world that have been poorly explored until recent times, while others were assigned species names of their own after being split by taxonomists from closely related species — until being split, the two fish were thought to be one and the same to be the same.
In 2009, an example of a new species being split from a relative was a diminutive brown knifefish; Brachyhypopomus gauderio. Described by ichthyologists Giora and Malabarba, it was formerly identified as Brachyhypopomus pinnicaudatus, but is differentiated morphometrically by having an extra curved bone below the operculum, and by the positioning of the anal and pectoral fins in relation to each other.
This is a species that’s seldom seen in the hobby, yet I luckily managed to get a group of juveniles. Growing to a maximum of 18cm, this was the perfect opportunity for me to keep some smaller knifefish — otherwise, I would have needed to carry out some major reconfigurations to my home to fit the size of aquarium needed to house some of the larger, more commonly encountered Gymnotiformes and witness their fascinating behaviours.
In the wild
Going from catch data and surveys that have been conducted across South America since 2009, we know that this species is widely distributed across the temperate regions of that continent. Its range spans four countries: Uruguay, Brazil, northern Argentina and Paraguay, and across multiple drainages including the Uruguay, Paraguay, Paraná and Tramandaí rivers.
Something common to these river systems is that they all have areas of slow-moving water — typically river banks, lagoons and flooded meadows — and this is where you’d most likely encounter B. gauderio. These waters are usually clear or lightly tinted by tannins but the lighting is dimmed by the abundant floating and emergent vegetation that are present, with Pistia stratiotes and Eichhornia crassipes both known to occur sympatrically.
Although underwater reports and images of these habitats are difficult to find, areas of submerged vegetation, leaf litter, sand or mud substrates, small sized rocks and large pieces of dead wood are what you’d expect to find hidden below the surface.
In the temperate regions of South America where this species lives, the water para
