There was an intensive trawl fishery in the Enonselka basin in Lake Vesijar
vi (southern Finland) in 1989-1993 and thereafter the fishing intensity dec
lined. The fish assemblage dynamics were studied both during the years of i
ntensive trawling and for 3 years afterwards. Roach Rutilus rutilus dominat
ed the fish assemblage before the mass removal. The intensive trawling effe
ctively diminished the roach stock and the present fishing intensity has be
en sufficient to prevent its recovery. There were significant decreasing tr
ends in the gillnet cpue (catch per unit effort) of bream Abramis brama (L.
) and bleak Alburnus alburnus (L.) while increasing trend was observed in c
pue of ruffe Gymnocephalus cernuus (L.) and vendace Coregonus albula (L.).
Perch Perca fluviatilis L. and pikeperch Stizostedion lucioperca (L.) showe
d variations in cpue but no trends existed. The proportion of cyprinids dec
reased while that of percids and coregonids increased in the catches. The c
hanges in the fish assemblage were induced by the intensive fishing and by
the concomitant decline in the ecosystem productivity. (C) 1999 The Fisheri
es Society of the British Isles.