TL/DR: where sea lampreys have been part of the ecosystem for a long time, they are a valuable part of that ecosystem. Where they are an invasive species, they

TL/DR: where sea lampreys have been part of the ecosystem for a long time, they are a valuable part of that ecosystem. Where they are an invasive species, they disrupt ecosystems and can nearly wipe out fish species that haven't co-evolved with them - but that doesn't mean the goal should be to exterminate them everywhere.