Which type of fish migrates from saltwater to freshwater to spawn?

The correct choice is anadromous fish, which are known for their unique migration patterns. These fish, such as salmon and certain species of shad, are born in freshwater environments, migrate to the ocean (saltwater) to grow and mature, and then return to freshwater to spawn. This life cycle allows them to benefit from the nutrient-rich environments of the oceans while ensuring that their reproductive processes occur in the traditionally safer conditions of freshwater, where predators are often less abundant.

Catadromous fish, in contrast, have a different migration pattern; they are born in saltwater and migrate to freshwater to grow before heading back to the ocean to spawn. Pelagic fish primarily inhabit the open ocean and do not typically engage in migrations between freshwater and saltwater for reproduction. Demersal fish reside near the bottom of the ocean and are not characterized by significant migratory behavior tied to freshwater spawning. Thus, the distinction of anadromous fish lies in their specific lifecycle that combines both saltwater and freshwater environments to facilitate spawning.