HABITAT Hatchetfish
THE HATCHET JOB
Forget everything you know about hatchetfish coming from slow waters as Tai Strietman discovers them thriving in a less than expected environment.
TAI STRIETMAN
A former aquarist at London Zoo, Tai is now based in Brazil where he is researching and studying fish.
TAI STRIETMAN
ONE OF my greatest joys involves delving into my books or searching online for information on fish and their habitats. There’s a wealth of information available but there’s always one thing which, after having been lucky enough to explore the wild habitats of some of our favourite species myself, never fails to make me grimace.
Look up any species and you will likely find a listed preference for water parameters, levels of flow, substrate, vegetation or other features, which are often based on the information collected at its type locality. Therefore, a species might be found over a sandy substrate in slow, warm waters full of leaf litter and tannins, and as far as the reader is concerned that’s the only environment that the fish will apparently accept. Well, neither fish nor environments are static; they move and they change.
Digging up the hatchets
Recently I went through a ‘reeducation’ regarding one of my favourite aquarium species, the Spotfin hatchetfish, Thoracocharax stellatus. I’ve kept them at home and following the general guidelines regarding all hatchets, they were housed in a warm, tannin-rich blackwater setup with very low flow. This was partly based on my experiences in the Colombian Amazon where I’ve collected Marbled hatchetfish, Carniegella strigata, from small forest streams.
But just because they are called ‘hatchetfish’ doesn’t mean that the nine member species of this group fall into a ‘one size fits all’ category.
Although Spotfins are recorded as coming from a range of habitats including clear-water streams, hatchetfish in general bring to mind sluggish waters. One trusted source, Fishbase, doesn’t even list them as inhabiting the Paraguay river basin, but they most certainly do!
I have collected Spotfins in the Miranda river in the Brazilian Pantanal; a wide, murky, yet strong-flowing lowland floodplain river. There I netted a few small individuals in the shallow margins at night. However, on an expedition in December 2020 to the Taquari river basin in Mato Grosso do Sul, Brazil, I found these fish in wickedly strong currents and at the bottom of powerful rapids, habitats that don’t exactly scream ‘hatchetfish’.