Fish stocking is the practice of releasing fish that are artificially raised in a hatchery into a natural body of water (river, lake or ocean), in order to supplement existing wild populations or to create a new population where previously none exists. Stocking may be done for the benefit of commercial, recreational or tribal heritage fishing, but may also be done for ecological conservation to restore or increase the population of threatened/endangered fish species that is pressured by prior overfishing, habitat destruction and/or competition from invasive species. Fish stocking may be conducted by governmental fisheries management agencies, non-profit organization and voluntary associations in public waters, or by for-profit NGOs, clubs and commercial enterprises in privately owned waters. When in public waters, fish stocking creates a common-pool resource which is rivalrous in nature but non-excludable. Thus, on public grounds, all can enjoy the benefits of fishing so long as fish continue to be stocked. Fish stocking is a practice that dates back hundreds of years. According to biologist Edwin Pister, widespread trout stocking in the United States dates back to the 1800s. For the first hundred years of stocking, the location and number of fish introduced was not well recorded; the singular goal of stocking was to enhance sport fishing regardless of ecological ramifications such as erosion of biodiversity. As Pister states, "When trout planting was first implemented, the nation was gripped with a highly utilitarian resource management ethic that placed short-term human interests above virtually any other consideration". Recently, the U.S. Fish and Wildlife Service along with state fishery branches have done a better job of recording exactly what species of fish are stocked at any given location. This began in the 1960s when research suggested the negative impacts of fish stocking on the ecological complexity of other life forms. The Wilderness Act of 1964 also opened the public's eyes to the impact stocking has on other organisms.