Salmo trutta morpha trutta, commonly known as sea trout, is an anadromous fish inhabiting coastal waters and freshwater streams in Europe. It has a silvery body with dark spots and displays remarkable adaptability, migrating between marine and freshwater environments for spawning. It plays a crucial role in nutrient cycling and is a key species in its ecosystem.

Salmo trutta morpha trutta, commonly known as the sea trout, is native to the coastal regions of Europe and western Asia. Its geographical distribution includes countries along the Atlantic Ocean and the Baltic Sea, such as the United Kingdom, Ireland, Norway, Sweden, Denmark, Finland, Germany, France, and Spain, extending to the Black Sea and the Caspian Sea regions.

Sea trout inhabit both freshwater and marine environments. They spawn in freshwater rivers and streams, requiring clean, well-oxygenated, and gravelly riverbeds for successful reproduction. During their marine phase, they occupy coastal waters and estuaries, preferring cooler temperatures typically found in temperate climate zones. They are often found in areas with abundant food sources, such as small fish and invertebrates.

The ecological niche of sea trout includes their role as both predators and prey within their ecosystems. In freshwater environments, they prey on insects, larvae, and smaller fish, while in marine waters, their diet expands to include crustaceans and larger fish. Sea trout are anadromous, meaning they migrate from the sea to freshwater to spawn, contributing to nutrient cycling between marine and freshwater ecosystems. Their presence in both environments makes them key species for maintaining ecological balance.