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).
Next - Section VI. Humans & the
River Mouths, Brackish & Estuarine Wetlands
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