Patterns of diel activity and species richness in young and small fishes of European streams: a review of 20 years of point abundance sampling by electrofishing

Originally developed to assess the relative abundance of >= 1+ fishes in large rivers, point abundance sampling by electrofishing (PASE) was adapted for 0+ fishes in the mid-1980s. Being both economical and widely applicable, PASE for 0+ fish has become a commonly used sampling approach in Europe, but its use for estimating 0+ fish density and species richness has attracted particular concern because of size and species selectivity. As such, this review is both timely and necessary. It summarizes the development of PASE and evaluates its various applications: studies of 0+ fish community composition, relative abundance and density, species richness (S), population size structure, larval and juvenile growth dynamics, microhabitat use, diel dynamics of species-species and species-microhabitat interactions, and the analysis of data emanating from PASE databases. The use and potential misuse of replicate sampling in estimates of S are examined, with PASE data from various European rivers re-analysed to assess geographical patterns in 0+ fish S. Comparisons of PASE and other approaches for estimating 0+ fish density and species richness have all demonstrated PASE to be cost-effective and relatively reliable, but sampling accuracy and precision do decrease as fishes enter the juvenile period of development.