The Lake Erie water snake subspecies (Nerodia sipedon insularum), which occurs mainly on the lake's western islands offshore from Ohio and Ontario, recovered to the point where on August 16, 2011 the U. S. Fish and Wildlife Service removed it from the Federal List of Endangered and Threatened Wildlife. The subspecies was first listed as threatened in 1999 after a decline due to eradication by humans, as well as habitat loss and degradation. When initially listed, the subspecies’ population had dropped to only 1,500 adults. Endangered Species Act (ESA) protections for the snake included designation of 300 acres (121 hectares) of inland habitat and 11 miles (18 km) of shoreline for breeding grounds. The introduction of an invasive species, the Eurasian round goby (Neogobius melanostomus) into Lake Erie in the mid-1990s became a new food source for the Lake Erie water snake. By 2009, the population recovered to 11,980 snakes, safely exceeding the population minimum goal of 5,555 adult snakes required by the 2003 recovery plan. Monitoring will occur for 5 years following this delisting. The Lake Erie water snake is just the 23rd species or subspecies to be removed from the list due to recovery.