Pescadero Creek - Ecology

Ecology

Intensive logging and watershed development, also beginning in the late 1920s or early 1930s, has dramatically increased sedimentation in Butano and Pescadero creeks. Both streams are listed under the federal Clean Water Act as impaired water bodies for sediment. Concerns about agricultural pesticide runoff into the marsh prompted a report prepared by DFG. Jong confirmed eutrophic (high nutrient) conditions in the marsh and found that algae blooms raise DO levels to saturation during the day and deplete levels during night respiration. Jong speculated that the low night DO could result in fish kills. The DFG study found levels of pesticides potentially toxic to fish in the sediment. In the mid-1980s the west bank levee of Butano Creek was breached about 50 feet downstream of Pescadero Road Bridge in order to reduce flood flows down the Butano Creek channel in the marsh. Breeches in other levees of the North Butano Marsh were also made to improve circulation.

Historically, both Pescadero Creek and Butano Creek, as well as several tributary streams, supported runs of Steelhead trout (Oncorhyncus mykiss) and Coho salmon (Oncorhynchus kisutch). Steelhead are still present, but there have been only sparse reports of Coho salmon in the watershed in recent years. Before logging removed much of the dense forest cover of this area in the middle of the 20th century, these streams were shaded, with frequent, stable pools created by fallen trees, bedrock outcrops, and boulders, and an abundant, if not steady, supply of gravel. With cool stream temperatures and reliable flows through the summer, they provided excellent habitat for salmon and trout, and both Pescadero Creek and Butano Creek were renowned sports fishing streams for vacationing San Franciscans in the late 19th century. According to a study by Professor Jerry Smith San Jose State University, estimates in 1985 showed that 10,000 steelhead trout were rearing in the lagoon. As of 2008, 750 steelhead were counted in the same area. With the exception of a few juvenile coho observed in Peters Creek in 1999, salmon have been absent from the watershed until a 2003 release of 17,000 hatchery-raised coho smolts in Pescadero Creek. Very few of these coho have returned to the creek.

California Golden Beaver (Castor canadensis subauratus) were re-introduced to Pescadero Creek around 1937-1938 by the DFG after near extinction in California in the early twentieth century. The beavers continue to thrive and although concerns about flooding related to beaver dams occurs, there is evidence that beaver in the lower channel in the 1950s reduced sediment movement through the system, especially since the late 1980s. Beaver improve salmonid abundance and size as their beaver ponds recharge the water table which, in turn, replenishes stream flows in the dry season and by providing ideal over-summering habitat. Contrary to popular myth, most beaver dams do not pose barriers to trout and salmon migration, although they may be restricted seasonally during periods of low stream flows. Physical evidence suggesting that beaver were once native to the area prior to extensive early nineteenth century fur trapping is a Castor canadensis subauratus skull in the Smithsonian Institution National Museum of Natural History collected by zoologist James Graham Cooper in Santa Clara, California on Dec. 31, 1855.