Growth of wels (Silurus glanis L.) in the Vistula River and the Zegrzyński Reservoir

The age of wels (Silurus glanis L.) and the back calculated length at subsequent ages were estimated using sections of the first pectoral fins. The growth of this species in the Vistula River follows the von Bertallanfy curve. Some fish grew faster in the Zegrzyñski Reservoir after its inundation in 1962 than they had before. The two populations exhibited an intermediate growth rate which was between that of wels from the Vag (Slovakia) and Don rivers (Russia).