Hydraulic Analysis of Resting Pool Preferences for Arctic Grayling (Thymallus arcticus) in a Nature-Like Fishway: A Case Study in the Northern Canadian Barrenlands

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Cody Kupferschmidt, Fred Noddin, David Z Zhu, Bill Tonn

Monday 29 june 2015

16:45 - 17:00h at Europe 1 & 2 (level 0)

Themes: (T) Hydro-environment, (ST) Ecohydraulics and ecohydrology

Parallel session: 3G. Environment - Ecohydraulic

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Fish habitat compensation projects and the study of ecohydraulics are becoming increasingly important in northern Canada, where diamond and metal mining developments have resulted in an increasing rate of lake destruction. Of 50 approvals issued for partial or complete destruction of lakes in northern Canada between the 1950s and 2005, 31 were issued in the most recent decade. Diavik Diamond Mines Inc. (DDMI) is located in the Barrenlands, a poorly studied region of northern Canada located in the Southern Arctic Ecozone. In fall 2012, DDMI completed construction of a habitat compensation project modifying a nearby existing stream by constructing a diversion channel to bypass a steep lower reach and creating nature-like fishway structures throughout the entire stream. The aim of this project was to enhance spawning habitat and connectivity in West Island Stream (WIS), an ephemeral stream that connects a 14 ha headwater lake to the 577 km² Lac de Gras. While several studies have focused on the ability of arctic grayling (Thymallus arcticus) to pass fishways, few have focused on their preferences for resting habitat within these fishways. This study aimed to evaluate the resting pool designs used in the WIS habitat compensation project by examining hydraulic preferences for resting arctic grayling in the bypass channel section. To study the resting pools, a Sontek FlowTracker handheld acoustic doppler velocimeter (ADV) was used to create 2-D velocity maps on a 10 cm grid for five pools suspected to have a high suitability for resting habitat. When required, a diesel pump was used to increase the flowrate of WIS to allow for ADV measurements in each pool under a total of three different flow conditions. Arctic grayling were placed in the stream for each of the three flow conditions and their use of resting habitat was evaluated using visual surveys and video recording. Arctic grayling resting habitat use was then compared with hydraulic characteristics and their preferences were determined. These findings can aid in understanding the complex ecohydraulics of nature-like fishways and offer improved resting pool designs for arctic grayling.