Spawning aggregation is defined as a group of fish of the same species that are gathered together for the purpose of spawning—releasing sperm or eggs for the purpose of reproduction. The fish population that is together at this time is significantly greater than during periods the fish are not reproducing. For fish whose habitat is stable, drawing aggregations revolves around a relatively small area. In transient populations the individuals might travel for days or weeks in order to reach the aggregation site.

The U.S. Fish and Wildlife Service (FWS) oversees the recovery of species listed under the Endangered Species Act. For fish, that goal is tended through the National Fish Hatchery System—coordinating efforts between hatcheries and fisheries management. As a result, national fish restoration programs have returned abundance to the populations of various species, including the Great Lakes lake trout, the Atlantic coast...