Pacus have several distinct physical features that differentiate them from other fish.
Their most notable characteristic is their human-like teeth, which are square and flat and resemble human molars (quite different from their piranha cousins' sharp, pointed teeth). This dental structure is unusual among fish and specially adapted for their natural feeding habits.
Aside from their human chompers, they're also pretty massive in size. Pacu fish can grow much larger than many other freshwater species. For example, the black pacu, a particularly large pacu species, can reach 3 feet (almost 1 meter) in length and weighs around 65 pounds (a little over 29 kilograms).
Fins and Body Shape
Their plate-shaped bodies are robust and somewhat rounded, distinguishing them from the more streamlined bodies of predatory fish.
Pacus are equipped with several fins that each serve specific functions, contributing to their adept maneuverability and stability in the aquatic environments of South America.
The dorsal fin, situated on the fish's back, plays a pivotal role in maintaining upright stability, aiding the pacu in navigating through slow-moving rivers and avoiding potential threats with ease.
This fin is particularly important for preventing the fish from rolling. It assists in making sudden turns and stops, which is crucial for a species that often dwells in environments with complex vegetation and varied topography.
They also have a well-developed caudal (tail) fin, which provides the propulsion necessary for swimming, chasing down food and evading predators. The anal and pelvic fins, located on the underside of the fish, further aid in stability and steering, allowing the pacu to make precise movements through the water.
The pectoral fins on its sides function like rudders, helping the fish steer and maintain balance.