Making heat maps of rivers to conserve salmon and trout

As water temperature in rivers and streams increase as a result of climate change, scientists are developing strategies for mapping critical cold-water habitat to guide conservation decision-making. Last month, more than 40 scientists from around the world, including ASF’s Graham Chafe and Jordan Condon, met at the University of Maine for a workshop to learn more about this technology.

Thermal infrared imagery is a powerful remote sensing technology that measures heat emitted by objects and can be used to create thermal maps of watersheds. Scientists fix cameras to aircraft and fly along the watersheds, capturing a series of images for later analysis. These cameras are creating temperature maps of the rivers and identifying where the water is warmer or colder than average, revealing habitat that would attract species like trout and salmon.

The health and sustainability of Atlantic salmon and brook trout populations are closely tied to the thermal characteristics of their river habitats. By mapping and analyzing thermal patterns, we can better understand how factors like climate change and habitat modification impact salmon. The use of aerial thermal infrared imagery, whether on a large scale by helicopter or at smaller spatial extents within rivers and tributaries, has proven extremely effective in identifying these critical cold-water areas.

Cold water refuges are critical for ensuring the persistence and resilience of cold-water fish species, including Atlantic salmon and Brook Trout, in the face of a changing climate. So, collecting information about thermal heterogeneity is the first step in prioritizing restoration actions or implementing protections to safeguard these vital habitats.

The workshop was co-organized by ASF Vice President of Research, Val Ouellet, along with NOAA Northeast Fisheries Science Center, Maine Department of Marine Resources, Inland Fisheries and Wildlife, and project SHARE. Held over two days, this workshop provided an in-depth look at the application of thermal infrared technologies in river systems. The workshop brought together three experts in the field: Steve Dugdale, associate professor at the University of Nottingham, Baptiste Marteau, lecturer at the University of Rennes, and Christian Torgersen, supervisory research wildlife biologist with the U.S. Geological Survey. Participants explored thermal dynamics and the importance of maintaining diversified thermal habitats to support resilient cold water fish populations. They then took a deep dive into the science behind the technology, including an overview of the platforms used for data acquisition, such as drones and helicopters. The workshop also focused on the skills and software required for analyzing thermal imagery and how the data can be used for habitat management and prioritizing restoration actions.

Val’s participation in this workshop reflects our commitment to staying at the forefront of research and technology in salmon conservation. The insights gained will be invaluable as we continue to develop strategies to protect and restore Atlantic salmon habitats.

When asked how ASF will use this technology moving forward, Val explained “The first step is to use this technology to assess thermal heterogeneity so that we can better understand the distribution of critical freshwater habitat for Atlantic salmon. This will guide our freshwater programs by helping us determine what conservation and restoration actions are needed and where.”

The workshop was funded by the Eastern Brook Trout Joint Venture, a network of fisheries managers, scientists, nonprofits, state and federal agencies, regional and local governments, businesses, conservation organizations, academia, scientific societies, and Tribal organizations that is working to conserve healthy populations of brook trout in the eastern native range.