Catfish of the Month Right Arrow April 2014 • Article © Heok Hee Ng, uploaded June 09, 2014

Weasel Catfish - Heptapterus mustelinus   (Valenciennes, 1836)

Rather than expound at length on how to maintain the subject of this month’s article (Heptapterus mustelinus) in an aquarium, I thought that I would start by telling you how the Planet Catfish forum (yes, this is a shameless plug) gave me the opportunity to maintain one of my dream catfish. Sometime in late 2003, someone had posted a query on the forum to identify a catfish for a friend that I managed to successfully identify as H. mustelinus. In the course of corresponding with the owner of the fish, it transpired that: (1) he lived less than an hour’s drive from me (this was when I was still a graduate student in the US) and (2) he wasn’t really keen on keeping the fish and offered to give it away. There are catfishes that one immediately desires to keep just from looking at photographs and this was definitely one of them for me. I became the owner of an 8” specimen of my dream catfish after a short drive to pick it up. Now that I had the fish, how was I going to maintain it? Information on the aquarium husbandry of this species is non-existent, since this is a species that very rarely shows up in the aquarium trade. I did have some information from the scientific literature about the biology of this species, and used that as a basis to set the fish up by itself in a 40-gallon tank with gravel substrate and PVC pipes for cover. I kept the fish for more than two years, until my graduation (and subsequent leaving of the country) forced me to give the fish away.

Heptapterus mustelinus is known from swift-flowing streams in subtropical and temperate South America. In Argentina, this species has been recorded from streams with moderately alkaline water (pH 7.5–8.8), moderate temperature (19–26°C) and current, and a substrate of gravel/rocks. Even though this data suggests that H. mustelinus are sensitive to deteriorating water quality, other studies in southern Brazil have shown that they are surprisingly resistant to habitat degradation due to urbanization, being able to withstand high concentrations of phosphorus, low levels of dissolved oxygen, and shallow water. It probably does better with water temperature in the cooler end of the spectrum (about 20–24°C): I maintained the heater at 22°C throughout the entire time I kept the fish; the water in water in my area was reasonably alkaline (pH about 9.0). Although its long, eel-like body (the specific epithet is Latin for “like a weasel” and probably a reference to its elongate body) and information about its habitat in the wild suggests that it does best with a current, my fish did very well without any significant water flow in the tank.

In the wild, this species feeds primarily on aquatic invertebrates; I found it to be very easy to feed in the aquarium, readily taking frozen and dried food. Although the fish had the tank all to itself for almost the entire period it was with me, there were occasional tankmates (mostly fish that were in the process of getting rehomed in another tank temporarily sharing its abode). I maintained medium-sized auchenipterids (e.g. Trachelyopterus) in the same tank without any problems. My H. mustelinus left tankmates alone as long as they were too large to be viewed as food.

I am very unlikely to have the chance to own this catfish ever again, but I will always be grateful to the Planet Catfish forum for giving me the opportunity for H. mustelinus to share two years of my life.

Copyright information for the images used in this article can be found on the species' full Cat-eLog page.

Jump to next section Cat-eLog Data Sheet
Scientific NameHeptapterus mustelinus  (Valenciennes, 1836)
Common NameWeasel Catfish
Type LocalityRio de la Plata, South America.
Synonym(s)Heptapterus eigenmanni, Pimelodus mustelinus
Jump to next section Species Information
Size 209mm or 8.2" SL. Find near, nearer or same sized spp.
General RemarksThe SL size given is at odds with Fishbase (which lists 9cm TL) for the same species, however the size given on this site is verified.
Jump to next section Habitat Information
DistributionSouth America: La Plata and Uruguay River basins and coastal drainages of southern Brazil.
La Plata (click on these areas to find other species found there)
La Plata, Uruguay (click on these areas to find other species found there)
Mar Chiquita, Dulce, Sali (click on these areas to find other species found there)
Show it on a map (Click the map-icon to show/hide map of species distribution)
pH6.0 - 8.0
Temperature18.0-24.0°C or 64.4-75.2°F (Show species within this range)
Other ParametersdH 6-10.
Jump to next section Husbandry Information
Jump to next section Further Information
ReferencesPoissons Amér. Méridionale - ppno p. - Pl. 2 (figs. 1-4)
Registered Keepers(1) Silurus.

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Breeding ReportsNone.
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Last Update2014 Jun 10 12:18 (species record created: 2014 Jun 09 19:39)

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