Professional Spotlight – Studying Arctic Charr Habitat in Maine
Greg Kronisch is a PhD student studying the movement ecology and diet of Arctic charr (Salvelinus alpinus) in Maine. These cold-water relatives of brook trout and salmon are found in North America, Europe, and Asia. Throughout their range Arctic charr exhibit a great diversity of size, body shape, and behavior in association with different habitats and diets. While anadromous (sea-running) populations are common in Canada, Alaska, and Europe, their range in the contiguous United States has receded over the past half a century to now only 12 native land-locked populations in Maine. Greg is advised by Dr. Nathan Furey at the University of New Hampshire, Drs. Michael Kinnison and Christina Murphy at the University of Maine on a National Science foundation project to evaluate Arctic charr diversity and ecology in the context of climate change.
Greg is continuing a 20-year project at UMaine that focuses on studying the Arctic charr in Floods Pond near Bangor, Maine which is one of the most southern populations in North America, putting them at risk from warming and species invasions. This population is among the healthiest and well-studied in Maine due in part to strict regulation of Floods Pond as the water supply for the city of Bangor. The long-term dataset on fish morphology, spawning behavior, and population size, and well-maintained access roads makes this the best lake to study Arctic charr in Maine.
A major part of this research relates to the movement and habitat use of Arctic charr using acoustic telemetry. For this work, fish are anesthetized and a special electronic tag is surgically implanted into the fish’s abdominal cavity. This tag then sends out a transmission every 1-3 minutes to receiving stations throughout the pond, providing information on fish location, depth, and body temperature. The advantage of this method is that the tagged fish only needs to be handled once, but analysis of these detections can produce up to 1,000 position estimates per fish each day (or 525,000 annually).
Initial testing of the receiving stations in April revealed that some receivers were unable to properly communicate, suggesting there might be issues with underwater obstructions. Because of this, Greg needed detailed information of lake depths and structures to set up his telemetry stations in locations that would avoid communication issues and “dead zones” associated with underwater reefs, holes, and large glacial boulders. Additionally, the habitat use of the tagged Arctic charr needs to be informed by an understanding of the lake morphology and available habitats. BioBase quickly come to the rescue for both needs!
Greg is leveraging the power of BioBase to stitch together side-scan sonar mosaics showing boulder fields and substrate types and has made great strides re-mapping the bathymetry of Floods Pond. Historically available maps of Floods, mostly based on fewer than 100 depth soundings taken with handlines in 1942, have turned out to be inaccurate in many locations. Once the lake is fully mapped, charr position estimates from the acoustic telemetry array will be used in conjunction with lake bathymetry and substrate hardness layers to better understand seasonal habitat use and spawning behavior of this state species of special conservation concern. Over the next few years Greg plans to map other Maine lakes to understand habitat available to other relic Arctic charr populations and to create habitat suitability models for lakes that do not currently have Arctic charr.
When asked how Greg would use the side-scan mosaic he said “I use these implanted tags and receivers to triangulate the fish’s positions every few minutes, but this isn’t terribly informative without also having habitat information. I’m using the physical lake data synthesized in BioBase to find if they trend toward certain substrate/bouldery areas, if they may use secondary deepwater spawning areas, where they are in the water column (ie fish depth vs bathymetry of that area), and how these may change seasonally.”
For more information about BioBase or other professionals using BioBase like Eli Kersh and LakeTech or completewaters check out other professional spotlight blog posts. Or for more information on the NSF and other research being done click the link. You can find more on Greg at his Grad Page or the Lab Website.
