The Wolf Pack

 

Scientific Name:  Hoplias aimara

Known Common or Trade Names: Giant Trahiras, Giant Wolf fish, Usually called ‘aimara’ It is important to understand that common names can be applied to many individual species and does not guarantee the correct identification of the fish in question.

Original Description:  Valenciennes, 1847 - French Guiana

Distribution and environment: Across most of the northern parts of south America, Brazil, Columbia, Venezuala , Guyana, French Guiana and Suriname.  Including  Rio Tocantins, Rio Xingu, Rio Tapajos, Rio Jar, and Rio Trombetas, in coastal drainages of the Guyanas, Suriname, and state of Amapa, Brazil. Hoplias aimara live in differing habitats including large rivers, rapids, waterfalls and flooded forest floor environments.

Size: The largest Hoplias species with the largest captured record at 120cm. The largest rod and reel record being  101cm. They will easily reach 50cm+ in aquaria and often much more.

Description:  A very large Hoplias species and follows the usual Hoplias elongated cylindrical shape. The colouring  is usually a variation of browns with a lighter base colour with a number of vertical patches or strips, usually small spots are visible on the upper front portion of the body onto the head,  the patterning can vary from location to location. See the site gallery to see some examples of this Hoplias aimara gallery. Some like the Amapa variant have a clean solid pattern where as the Venezuelan pattern is much more patchy.  The degree of colouration can vary greatly from almost solid black to light brown gold colour with very strong dark strips. The definitive was to ID an aimara is to look for a vertically-elongated dark spot on opercular membrane or edge of the gill plate, this can be seen on the image below identified by the red arrow.

 

Juvenile Description: The juveniles have a slim profile with relatively large eyes for their physical size. Because of their large eventual size they maintain this immature shape well up to 50cm.

Sexual Differences: Females are thought to be heavier in build.

Water parameters: Generally unfussy as long as extremes are avoided. Anywhere between a PH of 6.5 and 8 will be fine. Tropical temperatures of 23c – 30c

Tank Size: Because of the large size of the fish a large aquarium should be provided. 240cm x 90cm x 60cm – 96” x 36” x 24”.

Tank Setup:  A large open aquascape should be provided as these wolf fish are relatively active and like to hover mid water. They also seem to enjoy some high water flow perhaps related towards their existence in high flow waters. I have found them to be more active if provided with a good flow. They have been found in both flooded forest area and rocky rapids so there is some flexibility in creating a natural habitat. There is a great picture at http://www.amazon-below-water.com/gallery.html  - Chapter 9, Image 5 of an aimara in a rocky habitat. They are diurnal rather than nocturnal so will be seen during the daytime and unlikely to try and hide.

Compatibility: Considered to the most aggressive Hoplias species and one of the most aggressive aquarium fish. They are well known for attacking maintenance equipment and given the chance will go for your hand. It is very unlikely that you will be able to keep other fish with them. It has been done usually with big wolves and very small cohabitants. There are examples of immature specimens being kept with larger fish but until these fish get bigger we won’t know if they are successful or not. As with most large fish personalities can vary between individuals. My own personal theory to the aggressiveness of Hoplias aimara is that they live in rapids where suitable territory to hide and wait for passing food is scarce so they are very defensive of their patch.

Preferred diet: Aimara are not fussy eaters and will except most meaty foods, shrimps, crabs, crayfish, and fish meats are all accepted and variety will help ensure good health.

Breeding: Breeding is unknown in captivity but should require a vast aquarium. Successfully putting two together would be an achievement.

Availability: Once rare and very expensive they have become readily available although still expensive compared to most other fish. Only the Venezuelan/Columbian example is readily available as export form other locations is now illegal. When available other locality caught specimens are more expensive. They have been widely kept in Asia for some time now and apart from a few specimens have only recently become widely available elsewhere.   

Additional info:  Although originally described in 1847 by Valenciennes, a further description was carried out in 1907 by Pellegrin and named Hoplias macrophthalmus. Further studies were carried out and proved this to be the same species. As Hoplias aimara was used first that name takes precedence and the name Hoplias macrophthalmus is now defunct.

 

Author: Stephen Cousins 2010