News
May 29. - 2025
Physio-loggers to the Rescue: Tracking Sea Lamprey Parasitism in Lake Trout
Sea lampreys (Petromyzon marinus) are parasitic fish native to the Atlantic Ocean. Their populations spread into the Great Lakes in the mid-1800s, where they caused considerable harm to native fish such as lake trout, whitefish, ciscoes, and walleye. Sea lampreys feed by suctioning onto fish, using their tongues to rasp a hole through the skin, and consuming the blood and juices that flow out. Each sea lamprey can kill up to 18kg of fish during its parasitic stage. When populations peaked at nearly 2.5 million animals in the mid-1900s, sea lampreys were killing a staggering 45.000 metric tons of fish each year.
Rapid increase during Covid pandemic years
Science-based efforts to control Great Lakes Sea lampreys began in the 1950s, eventually causing populations to plummet to only about 10% of their historic highs. However, this battle is far from over as a recent paper [1] points out that reduction in lampricide application during the Covid pandemic years of 2020-2021 corresponded to a rapid increase in sea lamprey abundance. In Lake Ontario, sea lamprey population sizes increased over an order of magnitude (10x).
Lake trout implanted with heart rate and activity loggers
This brings us to a recent study led by researchers at Carleton University, in collaboration with five other institutions, aiming to develop a predictive model to detect sea lamprey parasitism on lake trout using implantable physio-loggers [2]. To do this, the team used two types of tags: Star-Oddi DST milli-HRT ACT tags, which record both heart rate and acceleration (HRA), and acceleration-only (AO) tags from another manufacturer.
Over the course of five trials, 33 lake trout were implanted with HRA tags yielding around 660 hours of data, and 25 trout were implanted with AO tags providing around 7800 hours of data. In total, around 70 different metrics related to heart rate and movement were evaluated to determine which could best signal a lamprey attachment event.
A step towards detecting parasitism in the wild
The results were promising. Body orientation and heart rate emerged as the most reliable predictors, with high classification accuracy. On average, trout showed a heart rate increase of 6.45 ± 1.3 bpm during lamprey attachment. Interestingly, trout that experienced non-feeding attachments (i.e., the lamprey attached but did not begin feeding) did not show a corresponding rise in heart rate—highlighting the specificity of the response.
While the study shows strong potential, the authors note that further refinements are needed. False negatives—likely caused by shifts in tag positioning—remain a challenge. However, the findings point to an exciting future: with acoustic data transmission and continued improvements to the model, bio-loggers could soon be used to monitor sea lamprey parasitism on lake trout in the wild.
[1] Marcy-Quay B, Lewandoski SA, Booth RM, Connerton MJ, Jubar AK, Legard CD, O’Malley BP, Prindle SE, Sumner AW, Symbal MJ, Todd A. Sea Lamprey control reduction during the COVID-19 pandemic corresponds to rapid increase in Sea Lamprey abundance. Fisheries (2025).
[2] Reeve C, Adams JV, Miehls SM, Lowe MR, Cooke SJ, Moser M, & Brownscombe JW. Developing a predictive model to identify Sea Lamprey parasitism on Lake Trout using biologgers. Transactions of the American Fisheries Society (2024).
Rapid increase during Covid pandemic years
Science-based efforts to control Great Lakes Sea lampreys began in the 1950s, eventually causing populations to plummet to only about 10% of their historic highs. However, this battle is far from over as a recent paper [1] points out that reduction in lampricide application during the Covid pandemic years of 2020-2021 corresponded to a rapid increase in sea lamprey abundance. In Lake Ontario, sea lamprey population sizes increased over an order of magnitude (10x).
Lake trout implanted with heart rate and activity loggers
This brings us to a recent study led by researchers at Carleton University, in collaboration with five other institutions, aiming to develop a predictive model to detect sea lamprey parasitism on lake trout using implantable physio-loggers [2]. To do this, the team used two types of tags: Star-Oddi DST milli-HRT ACT tags, which record both heart rate and acceleration (HRA), and acceleration-only (AO) tags from another manufacturer.
Over the course of five trials, 33 lake trout were implanted with HRA tags yielding around 660 hours of data, and 25 trout were implanted with AO tags providing around 7800 hours of data. In total, around 70 different metrics related to heart rate and movement were evaluated to determine which could best signal a lamprey attachment event.
A step towards detecting parasitism in the wild
The results were promising. Body orientation and heart rate emerged as the most reliable predictors, with high classification accuracy. On average, trout showed a heart rate increase of 6.45 ± 1.3 bpm during lamprey attachment. Interestingly, trout that experienced non-feeding attachments (i.e., the lamprey attached but did not begin feeding) did not show a corresponding rise in heart rate—highlighting the specificity of the response.
While the study shows strong potential, the authors note that further refinements are needed. False negatives—likely caused by shifts in tag positioning—remain a challenge. However, the findings point to an exciting future: with acoustic data transmission and continued improvements to the model, bio-loggers could soon be used to monitor sea lamprey parasitism on lake trout in the wild.
[1] Marcy-Quay B, Lewandoski SA, Booth RM, Connerton MJ, Jubar AK, Legard CD, O’Malley BP, Prindle SE, Sumner AW, Symbal MJ, Todd A. Sea Lamprey control reduction during the COVID-19 pandemic corresponds to rapid increase in Sea Lamprey abundance. Fisheries (2025).
[2] Reeve C, Adams JV, Miehls SM, Lowe MR, Cooke SJ, Moser M, & Brownscombe JW. Developing a predictive model to identify Sea Lamprey parasitism on Lake Trout using biologgers. Transactions of the American Fisheries Society (2024).