A Fish-Based Index of Biological Integrity for Assessing Ecological Condition of the Beaver River Watershed, Alberta, Canada

Increased growth resulting from urban development, agriculture and industrialization over the last century has resulted in land use modifications of Alberta’s landscape that pose serious threats to the biological integrity of aquatic ecosystems in the region, including the Beaver River watershed. Developing management plans driven by good understanding of the relationship between land use and aquatic ecosystem conditions are crucial to protecting these systems. In this study, we develop an index of biological integrity (IBI) for assessing the health of the Beaver River watershed (comprised of the Beaver, Amisk, and Sand rivers) using data collected on fish assemblages and a suite of physicochemical variables. We sampled 47 sites: 33 on the Beaver River, 12 on the Sand River, and 2 on the Amisk River; fish sampling was completed using boat electrofishing. Physiochemical and GIS data were used to assess the level of disturbance of each site. White suckers (Castostomus commersonii) represented 52% of the total catch while the sportfish species walleye (Sander vitreus) and northern pike (Esox lucius) represented less than 2% of the catch. Interviews with long-time anglers in the watershed indicate that sportfish have decreased in size and abundance over the past 30 years. We developed 13 candidate metrics based on the fish community and screened them for responsiveness to disturbance using multiple regressions and an information-theoretic approach. Four metrics (percentage of invertivorous cyprinids, number of benthic invertivores, percentage of omnivores, and percentage of lithophils) were significantly related to human disturbance and were used to calculate the IBI. The resulting multi-metric IBI was highly sensitive to change in cumulative anthropogenic disturbances represented by the variables human disturbance on bank and road density in basin; these disturbances are related to farming and petroleum extraction industry. The Sand River, the least human impacted zone of the watershed, had the highest IBI values. The upper Beaver and Amisk rivers showed the lowest IBI values reflecting poor aquatic health characterized by high nutrients values, low flows, and a high number of tolerant fish species. The IBI we developed is a useful tool for biological monitoring of the Beaver River watershed. It could be used in the future to assess the effects of industrial development and remediation strategies throughout the watershed on the health of the aquatic ecosystem.