Sea lamprey attach to fish with their suction cup mouths then attach their teeth into flesh. Once securely attached, sea lampreys rasp through the fish’s scales and skin with their sharp tongue. Sea lamprey feed on the fish’s body fluids by secreting an enzyme that prevents blood from clotting, similar to how a leech feeds off its host. Sea lamprey are native to the Atlantic Ocean and invaded the Great Lakes in the early 20^th century. In the Great Lakes, they are predators, with each individual capable of killing up to 40 pounds of fish over their 12-18 month feeding period. Only one in seven fish attacked by a sea lamprey will survive, either dying directly from the attack or from infections in the wound after the initial attack. Sea lampreys entered Lake Michigan around 1936 and subsequently infested several tributaries of the lower Grand River.

Sea lamprey spawn in streams, and their larvae live in those streams before they become parasitic. Sea lamprey control depends on a targeted  lampricide to kill the larvae or, in stream systems that are large (like the Grand River and its tributaries), barriers to prevent sea lamprey access to their spawning grounds.

How do we block sea lamprey but still provide passage for native and desirable fish species? This is a question plaguing the resource management agencies as conversations about removing aging dams/barriers and restoring connectivity are increasing across the country. There are options available to control sea lamprey but they must be evaluated on a case-by-case basis.

The Great Lakes Fishery Commission is leading the design and permitting effort for the upper reach project and has contracted with the U.S. Army Corps of Engineers to conduct an Environmental Impact Statement process that kicked off in April of 2019. 14 design alternatives have been developed for the upper reach where sea lamprey control will be evaluated and will undergo additional evaluation of impacts and feasibility through the EIS process. In 2021, the GLFC put the EIS process on hold until the permit for the Lower Reach project was near complete to avoid duplication of work. Once the EIS process resumes, additional analysis on the 14 alternatives, including the proposed Adjustable Hydraulic Structure (ASH) as proposed by the City and GRWW will commence.