Final answer:
The most abundant fish in Lake Titicaca is Orestias cuvieri, a small, silver fish caught using gillnets and hook-and-line methods.
Step-by-step explanation:
The most abundant fish in Lake Titicaca is A) Orestias cuvieri. This species is a small, silver-colored fish that is well-adapted to the high-altitude conditions of Lake Titicaca. Orestias cuvieri is typically caught using methods suited to its size and habitat, such as gillnets and hook-and-line techniques.
These methods are both selective and environmentally friendly, allowing for sustainable fishing practices essential for maintaining the fish population in Lake Titicaca.