River Mouths, Brakish and Estuarine Coastal Wetlands
V. Animals

The coastal river mouth is one of the most important and diverse wildlife corridors on the landscape. Due to dramatic reduction in freshwater inputs described and related human activity (see II. and Socioeconomic Uses section), wildlife around river mouths is much reduced in diversity and abundance. Anadromous fishes such as salmon and steelhead (see Anadromous Fishes section), and many amphibians (e.g. Santa Cruz long toed salamander, Red-legged frog, California tiger salamander) and reptiles (e.g. San Francisco garter snake, western pond turtle) have been dramatically reduced in number (Smith 1990, Rathbun et al. 1993). Many species of seabirds (e.g. Least tern), shorebirds (e.g. Snowy plover), waterfowl (e.g. Clapper rail), songbirds and raptors which once flourished are now much reduced in number or extirpated. The total abundance of birds using river mouths is orders of magnitude lower than 150 years ago (Grinnell 1922, Gordon 1996), except in Elkhorn Slough where the freshwater and brackish marsh have been converted to intertidal mudflat with intensive use by shorebirds (Ramer et al. 1991). Now-extirpated tule elk and grizzly bear once roamed the lower river valleys and coasts (McCollough 1987, Gordon 1996).

Relatively recent invasions of exotic aquatic invertebrates at Elkhorn Slough and potentially other coastal lagoons is another sign of habitat disturbance and degradation (Carlton 1975, Carlton and Geller 1993; and see Exotic Species Table).