NWT RESEARCH DATABASE

Regions: North Slave Region, South Slave Region

Tags: mining, biology, environmental baseline, fisheries assessment

Objective(s): The fisheries portion of this baseline program has three primary objectives: to identify the fish species composition in a subset of the lakes and streams near the Thor Lake project area, to identify existing fish habitat in those lakes and streams, and to measure the current levels of mercury, rare earth elements and other trace elements in fish tissues. A secondary objective of the program is to qualitatively determine the relative abundance of fish in the lakes.

Project Description: The fisheries portion of this baseline program has three primary objectives: to identify the fish species composition in a subset of the lakes and streams near the Thor Lake project area, to identify existing fish habitat in those lakes and streams, and to measure the current levels of mercury, rare earth elements and other trace elements in fish tissues. A secondary objective of the program is to qualitatively determine the relative abundance of fish in the lakes. Several gear types will be used for fish sampling in order to target the full range of fish species and sizes. Passive capture techniques, including gill nets and minnow traps, will be employed at the lakes. Electrofishing will be used for fish sampling in the streams. Lake morphometric measurements include bathymetry and surface and shoreline dimensions. Lake habitat features such as the type of substratum and the structure in littoral habitats will be recorded. The detailed stream habitat assessments will follow standard habitat assessment protocols. Water quality measurements of particular importance to fisheries assessment include dissolved oxygen and pH. Tissue and aging structure samples from a range of species and size classes will provide fish contamination baseline data. Tissue will be sampled from a minimum number of fish. Fish retrieved dead from gill nets will be preferentially sampled. Fish retrieved alive will be released unless they are required for tissue sampling. Baseline water quality will be assessed using water samples and water column profiles. Sediment samples will be collected to measure sediment quality parameters. Invertebrate community structure will be characterized using additional water and sediment samples. Ice thickness will also be measured in March 2009. Water quality will be assessed at the same lakes as the fisheries assessment, as well as Blatchford, Wasp, Ring, Porkchop, and five unnamed Lakes. Phytoplankton samples will be collected during spring and summer. Zooplankton and benthic invertebrate samples will be collected and examined for taxonomy and abundance. As much as possible, locals will be employed during the baseline study. Information including data and analysis on surface water hydrology and aquatics in and around Thor Lake will be available to locals and communities for review. The information may provide locals with a more thorough scientific overview of the local surface water hydrology and quality which can be used for various purposes (e.g. land use planning, economic development). The fieldwork for this study will be conducted from March 13 to October 30, 2009, in Thor Lake and around the Thor Lake area - 17 waterbodies in total, including six streams, within 5 km of Thor Lake (62° 6’ 20” N, 112° 35’ 50” W). The waterbodies include eleven lakes: Thor, Long, Elbow, Fred, Cressy, Thorn, Megan, and Kinnickinnick Lakes, two unnamed lakes, and a bay on Great Slave Lake. The six stream sites are two inlets to Thor Lake, the outlet of South Tardiff Lake, Fred Creek (both above and below Fred Lake), and the stream between Cressy and Fred Lakes.