Silurus glanis (Wels Catfish) Breeding Guide

Silurus glanis is a giant European catfish that nests and is guarded by the male; this guide covers its biology and why home spawning is impossible.

Overview

Silurus glanis, the wels catfish, is one of the largest freshwater fishes in Europe and a member of the family Siluridae. According to Wikipedia it is native to wide areas of central, southern and eastern Europe, in the basins of the Baltic, Black and Caspian Seas. Most adults are 1.3 to 1.6 m long; the longest recorded specimen measured 2.85 m (2023) and the heaviest authenticated catch weighed 134.97 kg.

Spawning Behaviour & Trigger

Wels catfish are highly fecund: according to Wikipedia, a female produces up to about 30,000 eggs per kilogram of body weight. After spawning, the male takes on parental responsibility and guards the nest throughout development. The species is a nest spawner, with the male defending the eggs until they hatch. Given that wild adults are most often 1.3 to 1.6 m long, even an average female can carry a very large number of eggs, which underlines why spawning happens on a scale far beyond aquarium dimensions.

Egg & Fry Care

Egg incubation depends strongly on water temperature, with hatching taking from three to ten days according to thermal conditions. The guarding male shows notable parental care: if water levels fall too quickly he has been observed to splash the eggs with his tail to keep them wet. This intensive male care continues through the vulnerable egg stage.

Common Challenges

Because adults reach several metres and tens of kilograms, and because spawning, nest defence and the huge egg masses occur on a scale suited to large ponds, lakes and rivers, deliberate reproduction is the domain of aquaculture and public aquaria. Home reproduction is impossible; the species should not be kept where it cannot reach full size safely.