Research & Science Note 1: Linking Aquatic Macroinvertebrates to Water Quality and Fish Habitat

Background

Decline in the biodiversity of freshwater aquatic organisms is now a globally-recognized concern. Such declines are best documented for relatively large and visible species (e.g. amphibians, unionid mussels), but they are also commonly reported for smaller, less well-known fauna.

For those cases where species declines are best documented, evidence is equally strong for dramatic, sometimes catastrophic, changes to the functioning of aquatic ecosystems. Losses of aquatic biodiversity and the associated impacts on ecosystem functioning have strong impacts on how aquatic ecosystems are managed.

Losses of aquatic biodiversity and the associated impacts on ecosystem functioning have strong impacts in the context of fisheries management.

Benthic invertebrates play a critical role in the flow of energy through riverine ecosystems. They typically function as key primary and secondary consumers and they are often favoured prey of keystone (and other) species of fishes. Declines in benthic invertebrate biodiversity are well documented. In a recent review of the literature, Haxton and Findlay (2007) showed that macroinvertebrate abundance and species richness was typically lower in dewatered reaches of rivers. Further, altered flows were associated with reduced abundance of specialist invertebrates, but not generalists. These results have clear implications to the management of riverine resources, especially for those species of fish that include macroinvertebrates as primary sources of food.

This project seeks to understand long-term changes in macroinvertebrate communities within 5 selected reaches of the Milk River, in southern Alberta. These sites were first sampled by Beth Cornish in 1986 (Cornish, 1988; Benthic invertebrate communities in the Milk River, Alberta and potential effects of a proposed impoundment) ). The sampling design developed by Cornish (1988),
which involved extensive replication and randomization, together with accurate species level identifications, provide a unique opportunity to evaluate changes over a period that includes both the highest (1995) and lowest (2004) river flows on record. The data collected in this study will be linked to land use, water quality and fish habitat.

This project is being undertaken in partnership with the Milk River Watershed Council Canada, University of Lethbridge, Sustainable Resource Development and Fisheries and Oceans Canada. This partnership creates a strong link for information sharing and exchange.

This study will provide critical information that will support the Milk River Watershed Management Plan. We thank the Stewardship in Action Program (Fisheries and Oceans Canada) for assisting with the funding of this important project.