Historic and Current Status of Fish in San Lorenzo Creek Watershed

The following is an excerpt from "Historical Distribution and Current Status of Steelhead (Oncorhynchus mykiss),Coho Salmon (O. kisutch), and Chinook Salmon (O. tshawytscha) in Streams of the San Francisco Estuary, California," October 2003, Robert A. Leidy (U.S. Environmental Protection Agency, Region 9 San Francisco, California 94105), Gordon S. Becker, Brett N. Harvey (Center for Ecosystem Management and Restoration, Oakland, Calfornia 94611)



San Lorenzo Creek Watershed

San Lorenzo Creek flows generally west, entering central San Francisco Bay near Roberts Landing, west of the city of San Lorenzo. The watershed consists of about 48 square miles, with highly urbanized lower and middle watershed areas. A 4.6 mile concrete channel runs from the mouth upstream. The upper watershed, including areas tributary to Crow and Palomares creeks, is less urbanized. Cull Creek Dam, located at RM 8.9 approximately 0.25 miles upstream from the Crow Creek confluence, was constructed in the early 1960s. The dam created a complete barrier to fish migration. Don Castro Dam, located immediately downstream of the Palomares Creek confluence, also was built in the early 1960s and also created a complete barrier to upstream migration.


San Lorenzo Creek

DFG surveyed San Lorenzo Creek from the mouth upstream 8.3 miles in April 1946. At an upper station near the B Street bridge (RM 7.77), steelhead (35-50 mm TL) were found to be abundant in shallow gravel areas (Shapovalov 1946). A local resident reported observing adult in-migrants in the year of the survey. The DFG survey also observed two steelhead, one each above and below tide gates near the mouth of San Lorenzo Creek. Oncorhynchus mykiss also were observed approximately 0.5 miles upstream from the tide gates. The survey report cited observations made by a local resident in 1941 or 1942 of 400 adult steelhead trying to ascend the concrete apron under the bridge on E. 14th Street in one day. DFG estimated that about 100 of these fish passed the apron (Shapovalov 1946).

DFG rescued 770 fingerling steelhead from drying portions of San Lorenzo Creek in 1955 (Allen 1957). These fish apparently were moved to other watershed areas with wetted channel persisting longer into the dry season.

A 1960 DFG stream survey of Crow Creek noted that small, sporadic steelhead runs occurred in the San Lorenzo Creek drainage (Allen and Moore 1960a). A 1961 DFG memo assessing the probable effects of several proposed Corps' flood control projects in the watershed also stated that the San Lorenzo Creek drainage appeared to support a minor steelhead run (Elwell 1961). The assessment estimated that there were 2.5 miles each of available spawning and nursery area of "mediocre" quality in the middle reach of San Lorenzo Creek (Elwell 1961). The assessment estimated a total of approximately 10.5 to 13.5 miles of spawning area considered "mediocre" and seven miles of "mediocre" nursery area scattered throughout the drainage. DFG considered the winter steelhead fishery to be of little or no value as it did not attract many anglers, and did not propose actions to conserve steelhead as part of mitigation for water and flood control developments in the watershed (Elwell 1961).

According to a 2002 assessment on fishery resources of the San Lorenzo Creek watershed, local landowners reported O. kisutch in the San Lorenzo Creek watershed through the 1960s (ACFCWCD and HES 2002). In a 1962 report, Skinner indicated that San Lorenzo Creek was an historical migration route and habitat for steelhead and/or coho salmon (Skinner 1962). At that time, the creek was said to be "lightly used" as steelhead and/or coho salmon habitat (Skinner 1962). In this reference, no distinction is made between use by steelhead and by coho salmon.

In August 1975, DFG visually surveyed San Lorenzo Creek from Don Castro Dam downstream to the inland limit of the concrete flood control channel at the Highway 238 crossing, a distance of 3.1 miles (Curtis and Scoppettone 1975b). Although no salmonids were observed, the survey report noted that San Lorenzo Creek was a historic steelhead stream (Curtis and Scoppettone 1975b). The report further noted that channelization, dam construction, flow regulation and urbanization of the basin, and siltation of gravels had an adverse impact on the steelhead resource. According to DFG, the downstream 4.3-mile concrete flood control channel likely was a barrier to steelhead passage as a result of high water velocity and absence of resting pools (Curtis and Scoppettone 1975b). The report observed that a program involving installation and maintenance of baffle plates in the low-flow channel to facilitate steelhead passage was terminated in 1963 with the construction of Don Castro Dam, which blocked access to principal spawning and nursery areas (Curtis and Scoppettone 1975b). The report concluded that San Lorenzo Creek did not appear to support a viable steelhead population and that the area below the reservoir should not be managed for trout (Curtis and Scoppettone 1975b).

A DFG memo from 1975 stated that rainbow trout lived in Don Castro Reservoir and main stem San Lorenzo Creek upstream from the reservoir (Anderson 1975a). The memo further noted that trout migrated upstream from Don Castro Reservoir into tributary streams to spawn during the spring months (Anderson 1975a).

As part of a fish distribution study, 11 sites along the entire length of San Lorenzo Creek were sampled during July 1981. Oncorhynchus mykiss was not found (Leidy 1984).

Spring migrant trapping, visual surveys for parr, and some electroshocking were performed on San Lorenzo Creek beginning in the Spring 1997 through the Spring 1998 as part of a masters thesis research project. No O. mykiss were observed or collected during the study (Kobernus 1998). The thesis concluded that the 4.6 mile concrete channel in lower San Lorenzo Creek was an impassable barrier to migratory fish. The thesis also identified four limitations in steelhead spawning and rearing habitat in San Lorenzo Creek, including few pools, lack of large woody debris, sedimentation of riffle habitats, and low abundance of benthic macroinvertebrates (Kobernus 1998).

As part of fisheries assessment, a July 1998 fisheries electrofishing survey of 16 sites within the San Lorenzo Creek watershed was conducted. A 305 mm TL fish was collected in San Lorenzo Creek downstream from Don Castro Dam and upstream from the confluence of Crow Creek (Hagar 1998). The survey report suggested that this fish may have come from Don Castro Reservoir because of its relatively large size. The second fish measuring 584 mm TL was collected from a large pool in San Lorenzo Creek downstream from the confluence of Crow Creek (Hagar 1998). The origin of this trout was not known, but the report considered that it was possibly anadromous. The report concluded that "the presence of trout in San Lorenzo Creek in July is an indication that the habitat may at least be capable of sustaining trout through the critical summer months" (Hagar 1998, p. 5). The report recommended further monitoring and analysis to determine whether water temperatures in the watershed were suitable for O. mykiss, and whether the 5.8 miles of channelized stream below the MacArthur Freeway was a barrier to adult steelhead.

ACFCWCD conducted a fisheries assessment, including fish sampling, of streams in the San Lorenzo Creek watershed during 2001-2002. Six San Lorenzo Creek sites were sampled, revealing four O. mykiss within a 75 meter reach upstream of the Castro Valley Creek confluence (ACFCWCD and HES 2002). In May 2002, staff of the ACFCWCD observed two O. mykiss in San Lorenzo Creek between Foothill Boulevard and 2nd Street in the city of Hayward. The fish were estimated to be between 380-510 mm in length (M. da Costa pers. comm.). It was not determined whether the trout had been "washed out" of Don Castro Reservoir or had migrated into the creek from San Francisco Bay.


Castro Valley Creek

Castro Valley Creek is largely underground in its lower reaches in the city of Castro Valley but has more natural reaches toward the headwaters. It flows generally south to join San Lorenzo Creek in the vicinity of Baywood School, east of Highway 238.

In January 1997, a large adult female O. mykiss was noted in the lower part of Castro Valley Creek (L. P. Kobernus pers. comm.). The fish appeared to be of hatchery origin. Three Castro Valley Creek sites were surveyed in 2001 as part of a fish study for the San Lorenzo Creek watershed. No O. mykiss were found (ACFCWCD and HES 2002).


Crow Creek

Crow Creek is a perennial stream draining an area of approximately ten square miles and is the largest tributary to San Lorenzo Creek. A 1,600-foot-long concrete box culvert was constructed in 1972 upstream of the Cull Creek confluence with San Lorenzo Creek that is a fish passage barrier.

DFG rescued four fingerling steelhead from drying portions of Crow Creek in 1955 (Allen 1957). These fish apparently were moved to other watershed areas with wetted channel persisting longer into the dry season.

In June 1960, DFG surveyed Crow Creek from the mouth to the headwaters, a distance of 5.5 miles. No salmonids were observed (Allen and Moore 1960a). However, the survey report noted that small, periodic steelhead runs were known to occur in the drainage (Allen and Moore 1960a). The report further concluded that Crow Creek likely represented one of the better spawning and nursery tributaries of the San Lorenzo Creek watershed. In years of normal runoff, parts of the creek were believed capable of supporting a small juvenile steelhead population throughout the summer period (Allen and Moore 1960a). This DFG report cited local residents who had observed O. mykiss between 150-200 mm TL being caught early in the trout season in the stream's lower reaches (Allen and Moore 1960a).

According to a 2002 assessment on fishery resources of the San Lorenzo Creek watershed, local landowners reported O. kisutch in the Crow Creek watershed through the 1960s (ACFCWCD and HES 2002). A 1961 DFG memo assessing the probable effects of proposed Corps' flood control projects in the watershed stated that Crow Creek contained the best steelhead spawning and nursery areas in the San Lorenzo Creek watershed (Elwell 1961). DFG estimated that three to four miles of spawning habitat and two miles of rearing habitat were available in Crow Creek (Elwell 1961). However, DFG did not propose actions to conserve steelhead and their habitat as part of mitigation for water development in the drainage watershed.

In a 1962 report, Skinner indicated that Crow Creek was an historical migration route and habitat for steelhead and/or coho salmon (Skinner 1962). At that time, the creek was said to be "lightly used" as steelhead and/or coho salmon habitat (Skinner 1962). In this reference, no distinction is made between use by steelhead and by coho salmon.

In July 1975, a pollution-induced fish kill in the vicinity of Crow Canyon Road included a 430 mm TL O. mykiss (DeSilva 1975). In August 1975, DFG visually surveyed the lower 8.2 miles of Crow Creek, essentially the entire stream length (Anderson and Scoppettone 1975). Above the confluence with Bolinas Creek, six O. mykiss were observed. One fish was netted and measured 230 mm FL, with the others of similar size (Anderson and Scoppettone 1975). The survey report noted that Crow Creek supported a minimal number of rainbow trout in its upper reach and offered poor spawning habitat but sufficient food (Anderson and Scoppettone 1975).

As part of a fish distribution study, two sites on Crow Creek were sampled in July 1981. No O. mykiss were collected (Leidy 1984).

ACFCWCD conducted a fisheries habitat assessment of streams in the San Lorenzo Creek watershed during 2001-2002, including fish sampling at six Crow Creek sites. Oncorhynchus mykiss were collected at two locations, one near the Cull Creek confluence and a second about one mile upstream. The former site yielded eight O. mykiss in a 115 meter reach, while the latter contained two individuals in a 138 meter reach (ACFCWCD and HES 2002). The report cites the sampling results as evidence of successful reproduction of rainbow trout in Crow Creek (ACFCWCD and HES 2002).


Cull Creek

Cull Creek is characterized by about seven miles of intermittent stream between the confluence with Crow Creek and the headwaters. It flows generally south to enter Crow Creek just downstream of the Cull Creek Dam. This dam, built in 1962, is a complete barrier to fish passage (ACFCWCD and HES 2002).

In July 1960, DFG visually surveyed the length of Cull Creek primarily by automobile with occasional stops to check the stream. No fish were observed, but the survey report noted that in 1957 or 1958, 50-100 mm O. mykiss were reported below a ranch pond spillway about midway along Cull Canyon Road (Rafra 1960). DFG estimated that there was little or no steelhead use in years of normal rainfall (Rafra 1960). Another report from the same survey stated that the stream probably received some use as a spawning area in some years (Allen 1960a). A farm pond dam located at about RM 4 was identified as a complete barrier to fish migration. DFG recommended that Cull Creek be managed as a steelhead spawning stream (Allen 1960a).

In a 1962 report, Skinner indicated that Cull Creek was an historical migration route and habitat for steelhead and/or coho salmon (Skinner 1962). At that time, the creek was said to be "lightly used" as steelhead and/or coho salmon habitat (Skinner 1962). In this reference, no distinction is made between use by steelhead and by coho salmon.

As part of a fish disribution study, one Cull Creek site was sampled in July 1981. No O. mykiss were collected (Leidy 1984).

ACFCWCD sampled three Cull Creek sites in April 2001 as part of a fisheries habitat assessment. No O. mykiss were collected (ACFCWCD and HES 2002).


Palomares Creek

Palomares Creek and its tributaries drain the hills east of the city of Castro Valley. This stream is an intermittent tributary to San Lorenzo Creek estimated to consist of about five miles of channel that joins San Lorenzo Creek near Don Castro Regional Recreation Area.

In June 1960, DFG surveyed the length of Palomares Creek by automobile with occasional stops to check the stream. In pools in the lower section, O. mykiss 38-89 mm TL were observed at an estimated density of 10-20 fish per 30 meters of stream (Allen 1960b). The survey report stated that historically Palomares Creek was probably utilized by steelhead as a spawning area, and that juveniles probably migrated to the lower part of the drainage, remaining in nursery areas in San Lorenzo Creek until they migrated to the Bay (Allen 1960b). The report also estimated that there was approximately three to four miles of "mediocre" to "fair" steelhead spawning areas, and recommended continued management of Palomares Creek for steelhead spawning (Allen 1960b). As part of a fish distribution study, two Palomares Creek sites were sampled below Don Castro Dam in July 1981 (Leidy 1984). No O. mykis were collected. DFG reported seeing rainbow trout in Palomares Creek in September 1987 (Gray 1987c).

In July 1996, Leidy electrofished Palomares Creek at the confluence with Eden Canyon Creek, opposite Palomares School. No O. mykiss were collected (Leidy 2002). ACFCWCD sampled four Palomares Creek sites in April 2001 as part of a fisheries habitat assessment. No O. mykiss were collected (ACFCWCD and HES 2002).


Eden Canyon Creek (Eden Creek)

This creek is tributary to Palomares Creek and consists of about three miles of channel between the mouth and the headwaters. A drop structure under Palomares Road and Interstate 580 on Eden Creek is a barrier to fish passage into Eden Canyon Creek (ACFCWCD and HES 2002).

In June 1960, DFG surveyed the length of Eden Canyon Creek primarily by automobile with occasional stops to assess the stream. No fish were observed. The study report concluded that Eden Canyon Creek had little value as a sport fishery (Allen and Moore 1960b).

As part of a fish distribution study, one Eden Canyon Creek site was sampled in July 1981. No O. mykiss were collected (Leidy 1984).

ACFCWCD sampled two Eden Creek sites in April 2001 as part of a fisheries habitat assessment. No O. mykiss were collected (ACFCWCD and HES 2002).

Assessment: Steelhead probably used much of the San Lorenzo Creek watershed historically, until channelization and other effects of urbanization led to degraded habitat and decreased population size. Steelhead were relatively abundant in this system into the 1950s (ACFCWCD and HES 2002). Construction of Don Castro Dam and Cull Creek Dam completely blocked anadromous fish migration into large portions of the upper watershed in the early 1960s. According to a fisheries assessment for the drainage, O. mykiss persists at extremely low frequency in the watershed, probably as a result of stocking in Don Castro Reservoir (ACFCWCD and HES 2002). The assessment report summarizes conditions in San Lorenzo Creek as follows: "Although suitable habitat for rainbow trout and steelhead exists in the watershed, passage barriers, excess fine sediment, and periodic poor water quality limit the numbers and distribution of these fish" (ACFCWCD and HES 2002, p. 1).


Allen, J. T. 1957. The 1955 fish rescue report for Region 3. CDFG.

Allen, J. T., CDFG. 1960b. Stream Survey Palomares Creek. Report dated June 18.

Allen, J. T., and R. Moore, CDFG. 1960a. Stream Survey Crow Creek. Report dated June 16.

Allen, J. T., and R. Moore, CDFG. 1960b. Stream Survey Eden Creek. Report dated June 16.

Anderson, K. R., CDFG. 1975a. Memo to S. DeSilva, and R. Houghtby, Warden. Re: Fishery resources of Upper San Lorenzo Creek, Alameda County. Dated August 27.

ACFCWCD, and HES. 2002. Fish habitat and fish population assessment for the San Lorenzo Creek Watershed, Alameda County, California. ACFCWCD, Hayward, CA.

Curtis, R., and G. Scoppettone, CDFG. 1975b. Stream Survey San Lorenzo Creek. Report dated August 20.

DeSilva, S., CDFG. 1975. Initial report of fish and wildlife loss: Crow Canyon Creek. Report dated July 8.

Elwell, R. F., CDFG. 1961. Memo to W. A. Evans. Re: San Lorenzo Creek and Cull Creek Projects, Alameda County. Dated June 9.

Gray, F., CDFG. 1987c. Letter to T. Palmisano. Re: Salmon and trout habitat in Alameda and Contra Costa County. Dated October 30.

Hagar, J., HEG. 1998. Technical memorandum to R. Wetzig, ACCWP. Re: San Lorenzo Creek fishery resource and habitat survey. Dated October 1.

Kobernus, L. P. 1998. Assessment of steelhead presence and habitat in San Lorenzo Creek watershed. M. S. California State University, Hayward, Hayward.

Leidy, R. A. 1984. Distribution and Ecology of Stream Fishes in the San Francisco Bay Drainage (and associated unpublished data, 1981-1984). Hilgardia 52(8).

Leidy, R. A., USEPA. 2002. Unpublished stream survey data 1992-2002.

Rafra, J., CDFG. 1960. Stream Survey Cull Creek. Report dated July 20.

Shapovalov, L., CDFG. 1946. Stream Survey San Lorenzo Creek. Report dated April 23.

Skinner, J. E. 1962. Fish and Wildlife Resources of the San Francisco Bay Area.