Traira and Trairao (Wolfish)
A Brazilian guide once referred to traira and trairão (known as guabina and aimara respectively in Venezuela) as giant bars of soap with mouths full of teeth. These ferocious, prehistoric looking fish, members of the Erythrinidae family of characins look like a cross between a bowfin and a carp. The traira (Hoplias malabaricus) is the smaller of the two species, usually well under 10-pounds. They are found from the northern Amazonian periphery in Venezuela all the way to central Argentina in the Paraná River drainage. These fish prefer slack water and will attack largemouth bass-sized topwater lures or fly rod poppers and sliders with reckless abandon. Don't forget your wire leaders though - one look at this fish's choppers and you'll understand why. A 7-8-weight rod spooled with floating line and a stout butt section tied to fairly heavy wire is just the ticket for these ugly but tough bruisers.
The traira's larger cousin, the wolfish or trairão (Hoplias aimara) is truly the stuff of angling nightmares. It attains weights in excess of 30-pounds and eats anything it darn well pleases. Big jerk baits, spoons, jigs, streamers and or large sliders/poppers fished in the eddies and pools adjacent to fast water are all susceptible to attack. Once hooked, this evil-looking fish thinks it's an obese tarpon and jumps repeatedly. Stout conventional tackle is a key to getting one of these bruisers in the boat. Anything less than an 8-weight rod, stout 4/0 stainless saltwater hooks, heavy butt and wire leader would be a big mistake as these monsters have a nasty reputation for heading headlong into the nearest available timber, rocks or current. The best place to catch these fish is in Northern Brazilian shield rivers such as the Rio Travessao or the aptly named Rio Trairao. Uraima Falls and the tributaries feeding into Venezuela's Guri Lake also hold a big population of these outsized beasts.
More about breathing air...
Traira, members of the characoid sub-family Erythrinidae, are examples of facultative (part-time) air breathers. Using vascularized (blood-rich) tissues in their skin, stomachs and swim bladders, this group of fish uses air to augment the oxygen they receive from water during hypoxic (low oxygen) conditions. This ability allows traira to utilize an unusual niche within their environment. They can often be found patrolling the very ends of quiet lagoons, or lurking, hidden at the edge of muddy, shallow shorelines. They suddenly explode into action engulfing any unwary bird, mouse or lizard that comes to the water's edge to drink.