Managing invasive species—not eliminating them altogether—is a better use of time and conservation resources in many cases,. Every year, hundreds of introduced species cause billions of dollars in damage to ecosystems, agriculture and infrastructure in North America alone. Dealing with the effects of invasion is particularly problematic in marine and freshwater habitats, because the pace at which invaders establish often greatly outstrips the resources available for their eradication. While most managers in North America now focus on ongoing containment and suppression interventions, they often lack quantitative guidance from which to set targets and evaluate success. Together with collaborator Prof. Stephanie Green (U Alberta), we have developed practical guidelines for identifying management targets for invasions for which eradication is unfeasible. We advocate “functional” eradication, which we define as suppressing invader populations below levels that cause damaging ecological impacts for high-priority locations. We summarize the key ecological information that managers will need needed to employ this strategy, including density–impact functions and recolonization rates. We have applied this framework for developing local suppression targets using three globally invasive species as examples: red lionfish (Pterois volitans), European green crab (Carcinus maenas), and rusty crayfish (Faxonius rusticus). Identifying targets for suppression allows managers to estimate the degree of removal required to mitigate ecological impacts and the management resources needed to achieve sufficient control of an invader.