1997/12/09 by Samuel C. Lohr, Kurt D. Fausch · 2 citations
Environmental Science · #Fish Ecology and Management Studies #Hydrology and Sediment Transport Processes #Wildlife Ecology and Conservation
paper · doi:10.2307/1447289
Much debate about natural variability of stream fish assemblages may stem from investigating them at different spatial and temporal scales, and analyzing data of different resolution. We assessed variability of stream fish assemblages over an 11yr period in a southeastern Colorado plains watershed based on surveys of 12 river and five tributary sites during 1983/1984, 1987/1989, and 1993/1994, and surveys of 40-48 pools along five tributaries during the last two periods. We analyzed across space and time using species presence/absence and relative abundance to assess how conclusions depended on scale and resolution of data. Assemblage similarity through time based on both types of data was higher for whole river or tributary faunas than at individual sites, because rare species that occurred sporadically at sites were consistently present at larger spatial scales. Assemblage similarity among river sites based on species presence/absence was moderate during 1987 and 1993 but lower during 1983 because of differences in passive sampling gear used. It was also low among tributary pools because of spatial variability in both rare and common species. In contrast, assemblage similarity among river sites based on species relative abundance was high for each survey because the same species were dominant but was often low at individual sites among surveys because of an unexplained 92% decline in Cyprinella lutrensis abundance from 1983 to 1993. Assemblage similarity among tributary pools based on species relative abundance in 1993/1994 was high for two tributaries where Lepomis cyanellus was dominant but low in others where it was often absent. The greatest change through time in assemblages at most tributary sites was apparently caused by drought after 1987/1989, which eliminated small pools and limited opportunities for recolonization. Conclusions about the natural variability of these fish assemblages depended strongly on scale, emphasizing the importance of multiscale investigations.