Thursday, June 14, 2018

More Adirondack Lake Trout Monitoring Needed

spawning lake trout Lake Trout are designated species of Greatest Conservation Need in NY, based on the reduction of cold, well oxygenated waters in lakes due to climate change.

Lake Trout, Salvelinus namaycush are one of two native salmonines to the interior Adirondacks, Brook Trout, S. fontinalis being the other.

However, unlike Brook Trout, which can be found from small headwater streams to deeper lakes, Lake Trout reside in the hypolimnion (bottom) of lakes during the majority of the year, where water temperatures are most suitable. The depth of the hypolimnion depends on many factors, including latitude, size of the lake, and the height of surrounding land that offers protection from the wind. 

Unlike Brook Trout, which has the Eastern Brook Trout Joint Venture to coordinate efforts, there are limited efforts to better understand our Lake Trout populations, including which water bodies still have sustainable, wild populations.

The Nature Conservancy’s Adirondack Chapter has been evaluating the climate resiliency of lakes based on lake characteristics where Lake Trout are thought to still occur. One recent study compiled the existing data, from the mid-1980s to 2014, and estimated that Lake Trout are present in approximately 102 Adirondack lakes, with only half of these lakes containing sustained populations, and approximately 36 lakes maintained by stocking. However, many of these lakes have not been assessed since the 1980s and the current status of the Lake Trout population is not well understood.

Our climate has warmed two degrees Celsius in the 20th Century and is predicted to warm another 2.5 to 10 in the 21st Century. With the warming climate we can expect to see warmer surface water temperatures and a longer period of lake stratification during the growing season, both detriments to Lake Trout survival and growth. While the lake bottom waters will remain cold due to water’s unique properties, they may not hold enough oxygen, especially late in the season. As temperatures warm, these longer periods of summer stratification, increased productivity, and potentially low or no oxygen in the bottom waters, may severely limit suitable habitat for Lake Trout.

In addition, recent studies on road salt impacts on our waterbodies may add another variable. For example, Mirror Lake in Lake Placid has a dense salt layer in the bottom water that has limited full mixing during spring turnover, limiting the amount of oxygen that recharges the bottom waters during this time. Lake bottom waters (hypolimnion) typically receive a fresh dose of oxygen during spring and fall turnover; during stratification, the hypolimnion is “cutoff” from the surface water and does not receive oxygen. Reduction in turnover events and increased length of stratification can further exacerbate the loss of oxygen in the hypolimnion, limiting suitable Lake Trout habitat.

Lake Trout are an iconic species in the Adirondacks, and throughout New York State, but data on their distribution and population status is lacking, and there is a need for updated assessments on many, if not all, of our lakes. Currently, there is no organized structure for tracking trends in the habitat quality of lakes for Lake Trout and other coldwater fish in Adirondack lakes and how they may be altered by climate change. We need to determine where Lake Trout still reside and then develop a monitoring program to determine the status of each population, prey resources, and habitat conditions and provide information to better inform management of this species.

The need to understand Lake Trout at this time is essential. Determining which lakes offer the best potential for preserving this species in the Adirondacks may be most successful for future management activities.

Photo of spawning lake trout courtesy U.S. Fish and Wildlife Service.

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Margaret Murphy

Margaret Murphy is a principal scientist and owner of Integrated Aquatic Sciences, LLC in Lake Placid and adjunct assistant professor at SUNY-ESF.  She has over 25 years experience in fisheries and aquatic ecology focusing on monitoring; physical, chemical, and biological assessment; and restoration of natural aquatic resources in the Adirondacks.  While growing up in Syracuse, she spent her childhood exploring the Adirondacks from her family camp near Old Forge and became a full time resident 5 years ago - fulfilling a life long dream of living and working in the Adirondacks - to work on conserving our aquatic systems and fisheries for future generations.  You can reach Margaret at margaret@integratedaquaticsciences.com




2 Responses

  1. Christine hildebrand says:

    Do the invasive species of plants like Eurasian Milfoil have any effect on the oxygen levels in the lake depths? Does the harvesting campaigns to remove the weeds have any effect?

    • Lake Trout are typically found in lakes with lower productivity. More productive lakes with more plants will tend to lose oxygen in the bottom waters faster due to oxygen consumption associated with the breakdown of these materials. I am not aware of studies that have assessed the effects of harvesting – but if the biomass is removed, there will be less material to decay.

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