Environmental variables and occurrence of 13 fish species

Species-environment relationships were studied between the occurrence of
13 fish and lamprey species and 9 mainly map-based environmental variables
of Finnish boreal small streams. A self-organizing map (SOM) analysis
showed strong relationships between the fish species and environmental
variables in a single model (explained variance 55.9%). Besides basic
environmental variables such as altitude, catchment size, and mean
temperature, landcover variables were also explored. A logistic regression
analysis indicated that the occurrence probability of brown trout, Salmo
trutta L., decreased with an increasing percentage of peatland ditch
drainage in the upper catchment. Ninespine stickleback, Pungitius
pungitius (L.), and three-spined stickleback, Gasterosteus aculeatus L.,
seemed to benefit from urban areas in the upper catchment. Discovered
relationships between fish species occurrence and land-use attributes are
encouraging for the development of fish-based bioassessment for small
streams. The presented ordination of the fish species in the mean
temperature gradient will help in predicting fish community responses to
climate change.