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Cetopsis coecutiens (Lichtenstein, 1819)

This month we welcome back our resident catfish contributor, Chris Ralph, writer and catfish expert in the U.K. fishkeeping magazines. This factsheet is close to my heart, so to speak, as I joined Chris and other catfish buffs on a memorable trip to Peru and the Amazon in 2000 and this catfish was one of the first that I had seen when we caught them from the boat on rod and line. They are not a pretty sight so I will let Chris explain and educate us on the "Whale Cat", Cetopsis coecutiens

etopsis coecutiens is one of the largest of the so called species of “Candiru” and is viewed with some trepidation amongst a number of catfish enthusiasts. Unfortunately or fortunately depending upon your personal views, Cetopsis coecutiens is not commonly available to the hobbyist. When this unusual catfish is available, expect to pay £20-£25 per fish. In their natural habitat these catfish are very much opportunist parasites feeding upon other fish, literally biting chunks of flesh from the body of their unfortunate victim. These catfish are often found inside the body cavities of larger fish such as the Red tail catfish – Phractocephalus hemioliopterus and Tiger shovelnose – Pseudoplatystoma fasciatum! These catfish are found in relatively large numbers in their natural habitats.

Cetopsis coecutiens

Cetopsis coecutiens belongs to the family Cetopsidae or Whale Catfishes from South America; namely the Amazon basin, Peru, Bolivia, Colombia, Ecuador, Venezuela and Brazil - Tocantins and Orinoco River basins.

Although it is documented that this catfish reaches a size of 265mm, whilst collecting catfish in Peru in July 2000 a number of specimens were caught on rod and line ( see image below) which exceeded this length and were 300mm+!

Cetopsis coecutiens = caught on rod and line

Cetopsis coecutiens prefer to be kept in water which has a pH in the range of 6.0-7.4. This catfish is ideally suited to temperatures in the range of 22-28ºC. Cetopsis coecutiens is naturally an open water swimming fish and as such requires well aerated water with a strong current in order to keep it in optimum conditions.

I would suggest a minimum size of Aquaria to be 72” x 24” X 24” if you are going to keep these catfish until they attain adult size. There is no real preference of substrate when keeping these catfish however; I would suggest good quality aquarium sand such as BD Aquarium Sand, or very smooth rounded gravel. The aquarium should provide minimal shelter in the form of rocks or bogwood due to the fact that this catfish is constantly on the go, swimming in the midwater regions of the water body. As with all other species of fish, water quality and general husbandry is very important, and I would recommend that a minimum of 25% water is changed on a weekly basis due to the fact that these catfish are constantly looking for food and the diet is fish or meat based. Lighting should be dim, due to the poor eyesight of these catfish and the fact that they are found at relatively deep water levels in their natural habitat.

Did you know? – This particular catfish was recently featured in the BBC series Amazon Abyss, and was seen still feeding upon the carcass of a catfish even after it was taken out of the water!

The body shape of Cetopsis coecutiens is described as being cylindrical, torpedo or cigar shaped. The body is also best described as being naked or devoid of scales. The pectoral fin spines are not serrated. The eyes are small in comparison to the rest of the body and are often described as being “piggy”. The mouth is relatively large in comparison to the rest of the body with the mandible being under slung, with the maxilla protruding, almost giving the appearance that the fish is smiling

The base colour of the dorsolateral region of the body and head is blue, whilst the ventrolateral region is predominantly white in colour interspersed with some patches of blue towards the head. The dorsal and caudal fins have some blue colouration whilst the remaining fins are white in colour.

Wherever possible I would recommend that the aquarist keep these catfish in a species only aquarium in small groups, but as the absolute minimum I would suggest two to three specimens assuming that they are available in these numbers. In their natural habitat Cetopsis coecutiens would be found in very large shoals. This catfish is not a species to be trusted in with other species due to its ability to bite lumps out of other large fish, and would soon devour any small fish within the confines of its environment. With this information in mind I would not recommend that you keep any other fish with these catfish.

As far as I am aware there are no documented records of Cetopsis coecutiens having been spawned in aquaria to date (but then who would want to?).

Sexual differences
The males tend to be more slender than the females. The dorsal fin of the male tends to be more pointed in mature specimens.

As with all the other catfish that I have had the pleasure to keep over the years, Cetopsis coecutiens readily accepts a mixed but meaty varied diet. I found that these catfish relished meaty foods such as whole mussel, cockles, prawns and earthworms and after a while they even accepted the occasional sinking catfish pellet! A word of caution though, these catfish will easily gorge themselves if given too much food, so you need to ensure that these catfish are not overfed.

Cetopsis: from the Greek cetos which means whale, and cosis which means like, hence the reference to this catfish being whale-like in appearance.

Ventrolateral: is defined as extending from below and to the side.
Dorsolateral: is defined as extending from the top to the side.
Maxilla: is defined as the bone of the upper jaw.
Mandible: is defined as the lower jaw.

Photo Credits
Chris Ralph

Factsheet 124

Silurus coecutiens, Silurus caecutiens
Common Name:
Blue Whale Catfish, Whale Catfish, Baby Whale Catfish, Blue Shark Catfish, Blue Torpedo Catfish or Candiru
South America; namely the Amazon basin, Peru, Bolivia, Colombia, Ecuador, Venezuela and Brazil - Tocantins and Orinoco River basins.
265mm s.l. (10½ins) (standard length – this is the measurement of the fish from the tip of the snout to the base of the caudal peduncle)
22 -28°C (71 -83°F)
6.0 -7.4.
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                                                                                                                                  Factsheet 124 = updated December 14, 2018 , © ScotCat 1997-2018 Go to Top