Investigating the potential impacts of water quality on kokanee salmon in the Mätʼàtäna Män (Kathleen Lake) Watershed, Kluane National Park and Reserve, Yukon

Abstract

The Kathleen Lake Watershed in Kluane National Park and Reserve is home to a land-locked population of kokanee salmon that experienced a dramatic decline in the number of spawning individuals starting in 2001. As of 2018, evidence supporting possible reasons for this population crash remained elusive. In 2018, a water quality investigation was initiated in the Kathleen Lake Watershed to see if water quality impairments might be impacting the health and spawning of the kokanee. Extensive monitoring by Parks Canada and Environment and Climate Change Canada from 2020 to 2022 documented turbidity events and high concentrations of certain metals, principally selenium and aluminum, in Johobo Creek, a tributary stream that discharges to Sockeye Creek just downstream of the kokanee salmon spawning area. As salmon essentially navigate by smell, they may avoid or delay migration to the spawning areas in the basin headwaters due to the turbidity and/or metal concentrations. Minerals, metals, and very fine sediments appear to be released and transported because of ground ice thaw associated with warm weather events in the basin. Although the metals are from a natural, geological source in the Johobo Creek headwaters, it appears that climate change may be impacting the magnitude and/or timing of the release of these metals and associated fine sediments to the kokanee habitat. To better assess the impacts of the metals and turbidity events on the kokanee spawning behaviour and success, future research should include assessing kokanee migration behaviour in response to turbidity events.