ANN ARBOR, MI—While the fishing community can be confident that sea lamprey numbers are set to decrease again this year due to aggressive controls that have been put in place by both US and Canada/Ontario stakeholders the past few years, this good news comes with a cautionary note as well.
“For two years there were very little controls put in place to decrease the sea lamprey population numbers,” said Marc Gaden, communications director and legislative liaison for the Great Lakes Fishery Commission (GLFC). This was due to the COVID-19 virus that effectively stopped sea lamprey controls in Great Lakes waters. “The huge spike in numbers that was found after two years of little being done to stem their population demonstrates that if we leave this for a short term the slimy beasts will bounce back.”
“This has to do with the fact that in 2020 the lamprey control season was a bust because crews couldn’t get out to do the normal control work and treatments,” said Mr. Gaden. “There was 75 percent less work carried out. And in 2021 again, the amount of controls and treatments decreased significantly.”
Mr. Gaden explained testing carried out by both USA and Ontario Canada officials in 2022 measures the survival rate of 2020 lamprey crop. “We expected to see a huge spike and this was the case. And again in 2023 studies on the survivor rates of 2021 we also expected a spike in their numbers because the amount of control work carried out was significantly reduced, and this was the case.”
“2022 and 2023 were very telling years because they we measured the amount of lamprey that had been exposed to (lampricide) treatment and control measures,” said Mr. Gaden.
“For 2022, 2023 and 2024 we are back to normal in terms of treatment of water and control measures for sea lamprey,” said Mr. Gaden. In those years, “we have been very aggressive in controls, and based on preliminary numbers we will be back to normal in 2024, back to pre-COVID numbers,” continued Mr. Gaden.
Mr. Gaden said with the sea lamprey numbers decreasing, “the fishery community can be confident the fish numbers will come back as well.”
Each sea lamprey can kill more than 40 pounds of fish during its lifetime. Before scientists developed chemicals and tactics to control the lamprey population, they were killing 110 million pounds of fish per year.
Prior to 2020 the GLFC had noticed an increase in lamprey numbers throughout the Great Lakes, so it had ramped up its treatment. But with the pandemic came restrictions and work teams couldn’t venture into the field to treat the streams, which had definite impacts to the treatment schedule.
“As I mentioned it just shows that you can’t leave them alone for even a short period of time,” said Mr. Gaden. “Sea lamprey are very opportunistic, and we had received a noticeable number of calls, letters and messages from anglers on the increase. We have been very aggressive the past couple of years, and we work very well with Ontario/Canada. It is critical that we work together.”
