by Bay Paulsen, Communications Specialist, GLIFWC Public Information Office
With resounding success in the last decades’ efforts to control the overwhelming population of sea lampreys in Gichigami’s waters and the native namegos (lake trout) being fully restored, readers may wonder what post-crisis management of this non-local being looks like.
Sea lampreys are a parasitic fish, native to the Atlantic Ocean but unintentionally introduced to the Great Lakes through man-made canals. Beginning life as larvae in rivers, they inhabit the sediment, where they filter feed. As they mature, they migrate downstream to the lakes where they feed on larger fish species by latching on with their unique suction-cup mouths and rasping tongue.
In its native ocean habitat, the sea lamprey encounters host fish that are generally larger and more abundant than those found in the Great Lakes. However, within the Great Lakes, a single adult lamprey can be a significant threat, capable of killing up to 40 pounds of fish during its lifetime.
During the larval stage when lampreys are found in river sediment, they are vulnerable to chemicals called lampricides, which are used to treat Great Lakes tributary streams annually and are a huge asset in the ongoing sea lamprey control efforts. These lampricides are harmless to most non-lamprey beings who inhabit the tributaries.
Annual lamprey monitoring
GLIFWC’s biologists continue to monitor adult sea lamprey populations by performing mark and recapture surveys each spring during the lampreys’ spawning season, when adult lampreys can be captured moving up those tributaries to reproduce. Traps are set during this time and checked daily. Up to 30 of the lampreys caught each day are marked on their dorsal fins and released back downstream from the trapping site. The number of lampreys with this mark that are recaptured gives biologists an estimate of the population in the tributary. Sea lampreys captured in excess of 30 each day are removed from the ecosystem.
Although current population estimates indicate lower sea lamprey numbers compared to pre-treatment levels, the fact remains that these non-local lampreys continue to be a significant threat to Great Lakes fisheries. While celebrations are in order for the restoration of the namegos fishery, it’s important to remember that vigilant observation, research, and action remains an important aspect in the long-term care of Gichigami.