A Fish-based Index of Biological Integrity for Assessing Ecological Condition of the Beaver River Watershed
Ariane Cantin and Tyler Johns
Urban development, agriculture and industrialization over the last century has resulted in land use modifications to Alberta’s landscape that pose serious threats to the biological integrity of aquatic ecosystems in the province, including the Beaver River watershed. Developing management plans that are driven by a good understanding of the relationship between land use and aquatic ecosystem conditions are crucial to protecting these ecosystems.
In this study, we developed an index of biological integrity (IBI) for assessing the health of the Beaver River watershed (comprised of the Beaver, Sand, and Amisk rivers) using data collected on fish assemblages and a suite of physicochemical variables. We sampled 50 sites: 31 on the Beaver River, 17 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 represented 52% of the total catch, while the sportfish species, walleye and northern pike, 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 regression and an information-theoretic approach. Five metrics (percentage of invertivorous cyprinids, percentage of benthic invertivores, percentage of omnivores, percentage of lithophils, and percentage of carnivores) 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. Road density had the strongest relationships to the IBI and its metrics, particularly percentage of benthic invertivores, percentage of lithophils and percentage of carnivores. All three of these metrics decreased with higher road density, while percentage of omnivores metric increased with road density. Road density in the study area is mainly related to agricultural and petroleum activities, with agricultural activities accounting for the major land use within the watershed.
The upper Beaver and Amisk rivers had the lowest IBI values, reflecting poor aquatic health, characterized by high nutrient values, low flows, and a high number of fish iii species that are tolerant of habitat degradation. The Sand River had the highest IBI values and the lowest levels of human disturbance. The lower Beaver River showed intermediate IBI values despite having high levels of agricultural activities and bank disturbance. However, the lower Beaver River has high flows of good quality water (inflow from the Sand River) and more diversified habitat than the Sand River. The IBI we developed is a useful tool for assessment and biological monitoring of the Beaver River watershed. It could be used in the future to assess the effects of industrial development and remediation strategies on the health of the aquatic ecosystems throughout the watershed.