Monday, May 04, 2015

Jerry Smith Studies 1995-1996

Pescadero Marsh Natural Preserve Salinity,
Tidewater Goby and Red-legged Frog Monitoring 1995-96

Jerry J. Smith
Dawn K. Reis

Department of Biological Sciences
San Jose State University
San Jose, CA 95192
June 25, 1997

A Report Prepared for the California Department of Parks and Recreation 3790-301-722(7)


The Pescadero Marsh, a 320 acre coastal wetland, includes an estuary/seasonal lagoon at the
confluence of Pescadero and Butano creeks, fresh and brackish water marshes, brackish water
ponds, and riparian areas along the streams. Modifications to the marsh complex due to past
human land uses include restricted water flow, due to a levee system throughout the marsh, and
reduced tidal prism, due to both the levees and sedimentation from land uses in the upper
watershed. Although it no longer functions as it did 150 years ago, Pescadero Marsh supports a high
diversity of animal and plant life, and is a refuge for a number of sensitive species (Smith 1990;
Jennings and Hayes 1990). Federally endangered tidewater gobies (Eucyclogobius newberryi)
use the lagoon and marsh habitats. Federally threatened California red-legged frogs (Rana
aurora draytonii) and federally endangered San Francisco garter snakes (Ihamnophis sirtalis
tetrataenia) use the fresher portions of the complex. Low salinity habitat (less than 4 parts per
thousand (PPT)) is required for California red-legged frog egg survival (Jennings and Hayes
1990), and relatively low salinity habitat (less than 7.5 PPT) is required for larval survival
(Jennings, pers. comm.). Tidewater gobies tolerate fresh or saltwater habitats, but avoid
strongly tidal areas when the sandbar is open (Smith 1990). North Marsh and Butano Marsh,
partially leveed wetlands in the northern and southern portions of the lagoon/marsh complex
(Figure 1), provide extensive habitat for both California red-legged frog and for tidewater goby,
but the quality of that habitat depends upon the timing of sandbar formation, water surface
elevations, the amount of flooded marshland and upon water salinity.

Portions of the Pescadero Marsh Restoration Project were implemented in the summer and fall
of 1993. One modification involved removal of portions of the levees separating North, Middle
and East Butano marshes (near water quality stations D3 and D6, Figure 1); previously an
opening had been made in the levee separating the eastern end of East Butano Marsh from
Butano Creek. These modifications allow Butano Creek flood waters to flow through the Butano
Marshes. They also allow tidal water, or water impounded by a closed sandbar, to move much
more easily throughout the Butano Marsh complex.

The second major restoration effort involved modifying the northern portion of the marsh
complex. A small culvert through the levee separating North Marsh and North Pond from
Pescadero Creek was replaced with 6 large culverts and two small culverts (water sampling
station B). In addition, a:levee that formerly separated North Pond was removed (north of water
sampling site C2).

Finally, a low levee (designed for + 5.5 feet) was added to separate North
Marsh from the channel leading to North Pond. Two large, normally-closed, culverts were
installed in the low levee (between water sampling sites C3 and Fl and between Cl and El).
One result of these modifications was to restore tidal action to North Pond, and the channel
leading to it, when the 6 large culverts are open; the culverts were to be left open except for
brief periods immediately following sandbar closure. The second intended result to was to
isolate North Marsh as a fresh-water to mildly brackish-water habitat for red-legged frogs and
San Francisco garter snakes. North Marsh would also serve as a potential refuge for tidewater
goby in case yellowfin goby (Acanthogobius flavimanus) became established in the saltier
portions of the marsh complex. The only open connection between North Marsh and the
remainder of the lagoon/marsh complex was to be a permanently open 12 inch culvert at +4.5
feet extending through the levee between water sampling sites Band El.

This report describes the results of water level and salinity sampling in 1994, 1995 and 1996 and
sampling for adult and larval frogs and tidewater gobies in 1995 and 1996. The monitoring was
designed to evaluate the functioning of the estuary/marsh complex in response to the restoration
actions and to propose additional management actions to maintain water levels, salinities and
other habitat conditions suitable for red-legged frogs, San Francisco garter snakes and tidewater

Check out Part 1 of this report here in pdf format.

Check out Part 2 of this report here in pdf format.


Help to Restore the Marsh!

*click to view


Heron and other predatory birds were seen feeding on the shorelines.

November 25, 2010

January 3, 2008

KGO news report 2010

KGO news report 2003