Stream Temperature Monitoring: Maintaining Cold Water Environments is a Hot Topic
In many parts of Canada, native trout, char, salmon, and grayling populations have suffered severe declines in both distribution and abundance within only a few decades. In Alberta, for example, these declines have led to populations of Bull Trout (Salvelinus confluentus) and Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi) being listed as threatened while Athabasca Rainbow Trout (Oncorhynchus mykiss) has been listed as endangered under the Federal Species at Risk Act. Alberta’s Arctic Grayling has also shown significant declines leading to their provincially designated sensitive status in Alberta. In southern Ontario, native Brook Trout (Salvelinus fontinalis) also has shown contraction in both range and numbers. Both Pacific and Atlantic Salmon are considerably diminished from former numbers with several populations being listed as either endangered, threatened, or special concern under the Federal Species at Risk Act and/or by COSEWIC.
The origins of these declines are often associated with the cumulative effects of increasing industrial, agricultural, and recreational activities and land use, hybridization and competition with invasive species, and climate change. Aquatic parasites and diseases such as whirling disease present another threat to these populations. One big stressor facing many of our native fish is increasing water temperatures. In Ontario for example, many small dams and increasing urbanization has led to stream temperatures warming remarkably faster than prior to these developments, often resulting in streams no longer being suitable for fish species that rely on cold water like Brook Trout.
Climate change is also reducing aquatic environments’ resilience. Many of Canada’s native fish species thrive in a narrow niche of coldwater ecosystems leaving them quite susceptible to any changes in these fragile temperature regimes. For example, Bull Trout tend to thrive in environments around 12° C and if water temperature often exceeds 18° C it is unlikely that Bull Trout will continue to persist in that environment. In order to recover depressed populations of native fish, it is imperative that we ensure aquatic ecosystems are as resilient as possible to be able to buffer changes in air temperature.
Water temperature monitoring is a strategy employed in many water bodies to help us understand if they are healthy. There are a variety of temperature monitoring tools but one we often use is the HOBO TidbiT water temperature data loggers which can be left in-stream for months at a time and record water temperature at a predetermined interval (example: every 30 minutes) and store the data inside the device. Depending on the type of logger used, sometimes we use a specially made housing for the logger. For example, many groups in Alberta commonly install loggers into a screw-on PVC end cap with holes drilled into it, then either use epoxy to attach the housing to bedrock or to a piece of rebar which is pounded down into the stream bottom. These data loggers are able to last in cold water conditions for several years on a single battery. When it is necessary to download the data, some devices use Bluetooth connectivity to wirelessly transmit all the data directly to a nearby smartphone or tablet. Some loggers need to be physically plugged into a computer. After downloading the data from the loggers, they can be further analyzed to help answer specific questions about the stream or watershed. In Alberta, stream temperature data can also be uploaded to the provincial Fisheries and Wildlife Management Information System (FWMIS) database where they are publicly available.
Stream temperature data can then help to inform decisions on fisheries management, habitat restoration, or disease risk. Stream temperature may influence the continued suitability of habitat for native fish in the face of changing climates; this may help inform future restoration stocking efforts or other recovery or management actions. Water temperature data can also be used to confirm the sources or areas where a watershed’s “fever” originates which can help guide restoration work. Stream temperature data are also used in areas where restoration work has been applied to monitor the effects of the work.
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