Fish movement through a nature-like fishpass within a small Arctic stream

  • Author / Creator
    Noddin, Duane
  • Resource development can lead to the harmful alteration, disruption, or destruction of fish habitat. During Diavik Diamond Mine, Inc.’s (DDMI) development of its facilities at Lac de Gras (LDG), NWT, DDMI destroyed two small headwater lakes and associated streams. To help offset this loss, DDMI developed a two-phase habitat compensation program, the M-Lakes and West Island Stream (WIS) projects, located in the LDG catchment, where fishpasses were installed to improve ecosystem connectivity and potentially increase each system’s productive capacity. A collaboration involving the University of Alberta, Fisheries and Oceans Canada, and DDMI worked to design, construct, and evaluate the effectiveness of the WIS nature-like fishpass, a modification of a 420-m headwater lake-outlet stream. The fishpass was designed to improve fish migration through the stream, which was naturally characterized by a series of small cascades and a poorly defined channel, preventing fish passage. My main objective was to evaluate the ability of fish to move throughout the modified stream. Successful movement would provide native fishes, particularly Arctic Grayling (Thymallus arcticus), access to spawning and rearing habitat. To conduct my evaluation, I PIT-tagged adult Arctic Grayling (n = 90), installed three paired antenna arrays, and manipulated stream flow to track fish movement during background (low) flow, and two manipulated (medium and high) flow regimes. A second experiment used the mark and recapture of fin-clipped young-of-year Arctic Grayling to determine the ability of these fishes to migrate downstream through the fishpass at naturally low summer flows. These field experiments revealed that the WIS fishpass established connectivity, albeit imperfectly. Although adult grayling could traverse through the most challenging lower part of the fishpass at medium and high flows, typical of their spring spawning season, I did identify a bottleneck to movement, particularly upstream movement. The section of stream that had the steepest gradient and a V notch structure created where two large rocks came together had the fewest recorded movement events and lowest passage efficiency. Noticeably more grayling moved during the hours of lower light (6pm to 6am), however, neither fish size nor in-stream water temperature affected movement. Young-of-year (YOY) grayling stocked at two upstream pools effectively migrated downstream throughout the steepest, and likely most challenging sections of WIS at the low summer flows that characterize Barrenlands streams when the YOY would be expected to move from their natal stream to their overwintering lake. Although the bottleneck section needs improvement, DDMI’s WIS compensation project achieved the goal of modifying a stream to provide grayling access to a previously unreachable habitat that could then be used for spawning and rearing. My research revealed that a base discharge of 10L/sec in a channel that was approximately one meter wide with a slope of less than 5 percent, would promote adult grayling movement. This discharge (or greater) was observed for a period of approximately 22 days in the spring of 2013, therefore, under comparable flows there would be time available for adult grayling to ascend, spawn, and descend West Island Stream. I also determined that YOY grayling could successfully navigate downstream at low summer flows of 1L/sec, with some of this movement occurring in the hyporheic zone through the hyporheic flow. PIT tags and antennas proved to be a valuable system for studying fish movement, allowing me to remotely record and document grayling movement, which mostly occurred at night.

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  • Degree
    Master of Science
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    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.