An estuary is a place where freshwater from a river mixes with saltwater from the ocean. Estuaries are often called a bay, sound, lagoon, inlet, or harbor. Estuaries are important because they are a very biologically productive ecosystem that supports many unique species. Estuaries contain many important habitats such as wetlands, mud flats, rocky shores, and seagrass beds. Estuaries serve as nursery and spawning areas. Almost 80% of the commercial and recreational fish we catch depend on estuaries for part or all of their lives. (Excerpted from National Estuary Program). Migratory birds use estuaries as rest stops where they feed and rest.

There are a total of 102 estuaries in the Unites States. About 30 of these have been deemed to be impaired in some way by either the state or federal government. Here on the Central Coast, Elkhorn Slough is an important estuary. The slough is an important stop for migratory birds and is considered one of the best birds spots in the world. The slough is also home to six endangered species and countless other animals.