A Fish-based Index of Biological Integrity for Assessing River Condition in Central Alberta
Cam Stevens and Trevor Council
Recent economic growth in Alberta has resulted in the conversion or modification of the majority of prairie-parkland ecosystems for agriculture, energy infrastructure, and urban development. The extent of, and rapid increase in human activities at the landscape scale may pose a serious threat to the integrity of aquatic ecosystems and the fish assemblages they support. We developed a multi-metric, fish-based Index of Biological Integrity (IBI) for assessing the health of aquatic ecosystems in central Alberta. Data on fish assemblages collected via electrofishing by the Alberta Conservation Association were combined with reach and basin-scale environmental variables for 80 river sites on the Battle River. We screened 12 candidate metrics representing attributes of the Battle River fish assemblage for redundancy, as well as their sensitivity to human disturbance variables, using regression and information theory methods. We selected three metrics for the IBI representing two trophic guilds (i.e., percent carnivores and percent omnivores) and one measure of community structure (i.e., species richness) that were unrelated to river size but related to measures of human disturbance. The multi-metric IBI was highly sensitive to changes in cumulative anthropogenic disturbances (statistically indexed as road densities). Regression analysis indicated that cumulative disturbances associated with road densities as low as 7 m/ha (i.e., 0.7 km/km2) in basins may impair the integrity of fish assemblages. The Battle River IBI provides a single, defensible, easily understood measure of the health of watercourses in the prairie-parkland ecoregion. With the aid of a simple spreadsheet, land managers and researchers can quickly calculate an IBI score using fish data collected from a river section. Additional research on ecological functions and requirements of species in northern systems is recommended to strengthen the basic foundation of guild-based bioassessment methods in Alberta.