Sorting out sea lampreys in the Great Lakes

March 25, 2019

Sea lamprey 2

by Harry Seely, BSc student

Atlantic sea lamprey (Petromyzon marinus) are an invasive species in the Laurentian Great Lakes and since their introduction, have required significant management and control practices to reduce their impact on native fish communities.  Lamprey are parasitic organisms that attach to a host fish and feed on its body fluids. Sea lamprey are native to the Atlantic Ocean and co-evolved with large Atlantic prey fish that probably survived lamprey attacks.  However, in the Great Lakes, this co-evolution did not occur, and sea lamprey function as predators rather than parasites, killing up to 20 kilograms of fish over their 12-18 month feeding period [2].  Atlantic sea lamprey were first discovered in a Lake Ontario tributary in the 1830s, having likely spread there from the Erie Canal [2]. These lamprey then spread to Lake Erie, and soon after in the 1920s, to the other Great Lakes during the reconstruction of the Welland Cannal that connects Lake Ontario to Lake Erie [3].  Since then, the introduced lamprey have disrupted food webs and contributed to sharp declines in host species such as lake trout (Salvelinus namaycush) and lake whitefish (Coregonus clupeaformis) [8]. 

In the Great Lakes, sea lamprey spend their juvenile lives out in the open water and return to small streams and tributaries during the spawning run where they become sexually mature and ready to reproduce as adults [2].  The newborn lamprey ammocoetes (larvae) develop in the tributary until they metamorphose into the parasitic juveniles and return to the lake [7].  It is the larval stage in the lamprey life cycle that has become the focus in the development of management strategies to control their populations. The primary method of reducing lamprey numbers in the Great Lakes has been through the use of lampricide chemicals (usually TFM) which are added to streams where the lampreys return to reproduce in order to kill the Fish_pass_1ammocoetes [8]. 

When lampricides are used to treat a stream, a specific lethal dose concentration is required for a certain period of time to effectively kill the ammocoetes without harming any other species.  However, for lampricides to work, they must be used in concert with physical barriers that help confine the lampreys to a manageable number of streams or sections of waterway where the chemicals can be added to the correct concentration. 

While these methods are highly effective in decreasing sea lamprey abundances, they can be costly and undesirable in some circumstances [8].  Although physical barriers such as dams help reduce the number of available streams for the lamprey to use as breeding grounds, many environmentalists and conservation groups are petitioning to have them removed as they can cause habitat fragmentation for other species [9].  Dam removal would increase the streams available for sea lamprey reproduction therefore, more funding would need to be allocated towards increasing lampricide treatments or other intensive sorting and removal.  Additionally, the increased use of lampricides could cause social concern, especially for local communities that live near streams being treated with the chemicals. However, most research has shown that TFM has no lingering effect on the environment and non-target fish usually recover after stream treatment [9].

Dr. Robert McLaughlin, a professor at the University of Guelph, researches the biodiversity of stream fish and how it can be impacted by physical barriers put in place to reduce sea lamprey numbers in the Great Lakes.  Specifically, he investigates key trade-offs between using physical barriers to reduce sea lamprey numbers, while still allowing for native fish to reach their spawning grounds upstream.  Dr. McLaughlin and one of his MSc students, McLean Smith, are contributing to a new system currently in development called FishPass.  FishPass is a passive sorting facility for researching different methods to sort out sea lampreys from other fish that may be travelling upstream with the ultimate goal of preventing sea lamprey reproduction [2]. 

FP_schemaDr. McLaughlin and McLean are currently researching possible sorting systems including sized-based approaches such as different trap opening size, the effects of water velocity (attraction flow) and even the potential use of light.  Since lamprey are nocturnal and hide during daytime, light could be used as a potential deterrent and can actually attract other species of fish as well.  Research being conducted at Michigan State University is also investigating potential methods of passive sorting that could be used in FishPass such as the use of  pheromones and alarm chemicals to draw in or defer lamprey to specific compartments in a barrier while allowing other fishes to bypass the barrier.

FishPass is a promising system as it would reduce the amount of habitat fragmentation for native fish but would still allow for the use of barriers that are necessary for lampricide treatments. The issue surrounding the sea lamprey invasion in the Great Lakes is multidisciplinary, involving economic, social and ecological challenges.  However, the potential of innovative systems such as FishPass will hopefully reduce sea lamprey populations and restore balance to the biodiversity of the Great Lakes.



1 – Eshenroder RL, Burnham-Curtis MK. Species succession and sustainability of the Great Lakes fish community. 1999. In: Taylor WW, Ferreri CP, editors. Great Lakes fishery policy and management: A binational perspective [Internet]. East Lansing, MI: Michigan State University Press. p. 145–84. Available from:

2 – Great Lakes Fisheries Commission -

3 – Mandrak NE, Crossman EJ. 2008. Postglacial dispersal of freshwater fishes into Ontario. Canadian Journal of Zoology 70(11):2247–59.

4 – Manjon PJ and Hanson LH. 1980. Spawning behavior and fecundity of lampreys from the upper three Great Lakes. Canadian Journal of Fisheries and Aquatic Sciences 37(11): 1635-1640. 

5 – Morse TJ, Ebener MP, Koon EM, Morkert SB, Johnson DA, Cuddy DW, Weisser JW, Mullett KM, and Genovese JH. 2003. A case history of sea lamprey control in Lake Huron: 1979 to 1999. Journal of Great Lakes Research 29:599-614.

6 – Rahel FJ and McLaughlin RL. 2018. Selective fragmentation and the management of fish movement across anthropogenic barriers. Ecological Applications 28(8):2066–2081.

7 – Shetter DS. A Brief History of the Sea Lamprey Problem in Michigan Waters. 1949. Transactions of the American Fisheries Society 76(1):160–76.

8 – VeĢlez-Espino LA, McLaughlin RL, and Pratt TC. 2008. Management inferences from a demographic analysis of sea lamprey (Petromyzon marinus) in the Laurentian Great Lakes. Canadian Journal of Fisheries and Aquatic Sciences 65(2):227-44.

9 – Wilkie MP, Hubert TD, Boogaard MA, Birceanu O. 2018. Control of invasive sea lampreys using the piscicides TFM and niclosamide: Toxicology, successes & future prospects. Aquatic Toxicology.