Heptapterus mustelinus
Weasel Catfish - Heptapterus mustelinus   (Valenciennes, 1835)

Article © Heok Hee Ng, uploaded June 09, 2014.

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.

Down Cat-eLog Data Sheet
Scientific Name Heptapterus mustelinus  (Valenciennes, 1835)
Common Name Weasel Catfish
Type Locality Rio de la Plata, South America.
Synonym(s) Heptapterus eigenmanni, Pimelodus mustelinus
Down Species Information
Size 209mm or 8.2" SL. Find near, nearer or same sized spp.
Identification Deprá et al. (2022) redescribed the genus Heptapterus as having the following shared features: (1) Adipose fin extensively fused with the caudal fin; (2) caudal fin non-bifurcate (i.e., caudal fin not divided in two lobes; vs. bifurcate, with distinct dorsal and ventral lobes); (3) dark bars and stripes on back of trunk (vs. absence of dark bars and stripes on back of trunk); (4) 5-6 pairs of pleural ribs (vs. 8-9 ribs); (5) elongate body with a head length of 16.1-24.9% (vs. 25.5-27.3%); (6) posterior extension of mouth rim short, with rictus barely reaching vertical line through posterior nostril (vs. posterior extension of mouth rim longer, with rictus reaching vertical line between posterior nostril and eye); (7) premaxillary tooth plate with no posterolateral extension, or with a small one (vs. with a very long posterolateral extension); (8) pelvic-fin insertion posterior to vertical through insertion of dorsal fin (vs. anterior) and anal-fin insertion posterior to vertical through adipose-fin origin (vs. anterior); (9) 10-23 anal-fin rays (vs. 33-46); (10) anal and caudal fins separated (vs. anal fin confluent with the caudal fin); and (11) supraorbital pore 6 (s6) fused or closer to each other (vs. separate and closer to the eye than to each other).
General Remarks The 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.
Down Habitat Information
Distribution South 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)
La Plata, Uruguay, Upper Uruguay, Pelotas (click on these areas to find other species found there)

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IUCN Red List Category Not Evaluated
pH 6.0 - 8.0
Temperature 18.0-24.0°C or 64.4-75.2°F (Show species within this range)
Other Parameters dH 6-10.
Down Husbandry Information
Breeding Unreported.
Breeding Reports There is no breeding report.
Down Further Information
Reference Voyage dans l'Amérique méridionale, pp Pl. 2 (figs. 1-4).
Registered Keepers There is but a single registered keeper, view all "my cats" data.
Wishlists Love this species? Click the heart to add it to your wish list.
There is no wish to keep this species.
Spotters Spotted this species somewhere? Click the binoculars!
There are 6 records of this fish being seen, view them all.
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Look up on Encyclopedia of Life Look up Heptapterus mustelinus on Encyclopedia of Life
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Heptapterus mustelinus QR code LFS label creator
Last Update 2022 Sep 10 01:54 (species record created: 2014 Jun 09 19:39)

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