This Data Nugget lesson begins with a phenomenon: an introduced crab species is killing native plants in a marsh ecosystem. The invasive European green crab, introduced into the Great Marsh ecosystem on the North Shore of Massachusetts, uproots eelgrass, a native saltwater plant species, when the crab digs up the bottom looking for food and shelter. Scientists want to know how to reduce the harmful effects of the green crab on eelgrass. Data on the number of female and male green crabs found at 13 different locations in Essex Bay (an area within the Great Marsh) are provided to students with the driving question, “What locations in Essex Bay are the most promising for eelgrass restoration, based on the number of invasive green crabs?” The lesson involves calculating totals and “suitability score” (explained in the Data Nugget lesson), mapping data, making a claim, and providing evidence and reasoning to support the claim. Students are also asked to suggest further questions to investigate and to formulate a hypothesis to test one of their questions. A teacher guide is available by email request and a student activity sheet is provided.