Long-term dynamics of pelagic fish density and vendace (Coregonus albula (L.)) stocks in four zones of a lake differing in trawling intensity

An 11-year time series of hydroacoustic fish density estimates and fisherie s statistics of vendace (Coregonus albula (L.)) from four zones of a lake d iffering in trawling intensity was analyzed in order to test the hypothesis that intensive trawling has detrimental effects on pelagic fish stocks, es pecially vendace recruitment. The standardized fish density estimate in tra wled zones showed no decrease in comparison to the non-trawled zone. No sig ns of recruitment failure associable with trawling intensity were found. Th e growth of vendace at the end of the study period was slower than that at the beginning, indicating a higher density, most clearly so in the zone wit h highest trawling intensity. No significant correlations were detected bet ween 3-year mean trawling intensity and yield per unit effort of over-1-yea r-old vendace or fish density in any zone. Thus, no evidence to support the hypothesis was found. This was suggested to be due to density-dependent co mpensatory processes in recruitment and/or natural mortality effectively co unteracting the population change induced by exploitation.