Wels Catfish

The wels catfish is a massive, scaleless freshwater predator native to large rivers, lakes, and reservoirs across central, eastern, and southeastern Europe and western Asia. It is one of the largest freshwater fish species in the world, with confirmed adults regularly exceeding two meters and historical records suggesting even greater sizes. As an apex predator in its native ecosystems, the wels catfish has also been introduced to river systems in western Europe, where it has established populations outside its historic range and is regarded as a significant top predator among introduced freshwater species.

• Extremely elongated, scaleless, eel-like body that can exceed 2 m in large adults
• Mottled olive-brown, grayish, or nearly black coloration on the back and flanks, paler on the belly
• Very broad, flattened head with small eyes set well forward
• Long pair of barbels on the upper jaw (often reaching past the pectoral fins) plus four shorter barbels on the lower jaw
• Long, low anal fin running much of the underside; small, rounded dorsal fin set far forward

Its scaleless skin, broad flat head, and long jaw barbels readily distinguish it from all other large European freshwater fish.

Wels catfish inhabit large, slow-flowing rivers, lakes, and reservoirs across its native range spanning central and eastern Europe through the Danube, Volga, and other major river basins, into western Asia. It favors deep pools, undercut banks, sunken wood, and other structure offering cover during the day, becoming more active at dusk and at night. It tolerates a broad temperature range but is most active in warmer months, often becoming sluggish and retreating to deep holes during cold winter periods. Introduced populations now also thrive in rivers and lakes of western Europe.

This is a largely nocturnal ambush predator that rests in deep cover during the day and hunts actively after dark, using its sensitive barbels to detect prey in murky or low-light water. Diet consists mainly of other fish, along with invertebrates, amphibians, and occasionally waterfowl taken by large individuals. Spawning occurs in warm months, when a pair builds a shallow nest among vegetation or roots in which eggs are laid and guarded, primarily by the male, until hatching. As one of the largest predators in its ecosystem, the wels catfish plays an important top-down role in freshwater food webs across its native and introduced range.