Titus, R. G., D. C. Erman, and W. M. Snider: History and status of steelhead in California coastal drainages south of San Francisco Bay. In preparation. San Pedro Creek Drainage San Pedro Creek is somewhat unique in that it is a highly urbanized stream which continues to support a naturally reproducing steelhead stock, in part due to the interests and efforts of local residents in the community of Pacifica. From an historical perspective, the CDFG files indicate that adult steelhead were seen ascending the stream to spawn in April 1941. At that time, ranches dominated the drainage area and it is assumed that the creek system was in relatively good condition. There was tidewater at the stream mouth, but no real lagoon. The main stem was about 4 km long and formed by flow from three forks, the "east" fork being the only one with perennial flow. Water was diverted from the creek system for irrigation. However, by 1971 the creek habitat was severely degraded due to the effects of garbage dumping, rat poisoning, and wastewater discharge in conjunction with urbanization of the area. Apparently, a fish kill had occurred on 22 December 1970. Local citizens formed a committee to promote the protection and enhancement of San Pedro Creek (J. Ladd, CDFG, unpubl. memo. of 14 January 1971). Two adult steelhead were seen in the stream during a single spot check on 6 April 1972 (E. Armstrong, CDFG, unpubl. memo. of 7 April 1972). Adults ascended the stream during the winter of 1972-73 as well (D. C. Erman, UC Berkeley, unpubl. letter of 9 February 1973). San Pedro Creek was surveyed by the CDFG in July 1973. Urban debris was still common in the streambed, and spawning areas were both quantitatively and qualitatively limited. Rearing habitat was adequate, with the presence of pools and abundant riparian cover. Several barriers to upstream migration were identified, especially at culverts, and several diversions were observed, the largest being that for the North Coast County Water District. Storm drains discharged into the creek. Juvenile steelhead were observed in all reaches of the main stem. As determined from electrofishing samples, the trout ranged from 3.8 to 20.3 cm in length and averaged 8.9 cm. Steelhead were observed above all culverts on the main stem, but only below the water district diversion in the south fork of the creek system. The size-structure of the juvenile steelhead population in San Pedro Creek was investigated on four occasions during the 1970's. On 3 July 1973, steelhead were sampled by electrofishing at four main stem stations (K. R. Anderson, CDFG, unpubl. memo. of 29 August 1973). The fish ranged in size from 3.6 to 16.0 cm FL, and averaged 8.0 cm FL (SD = 1.8 cm, n = 220). Thus, rearing juveniles were age 0+ and 1+, and 0+ trout were proportionately dominant in number. Abundance estimates were also made in late summer 1973, by electrofishing seven stream reaches (15–61 m) and applying the two-pass removal method of population estimation (K. R. Anderson, CDFG, unpubl. memo. of 13 November 1973). Juvenile steelhead densities ranged from about 2.0 to 7.6 trout/m, and averaged (± SD) 5.1 ± 2.3 trout/m. Despite its somewhat degraded condition, the creek system continued to support relatively high densities of juvenile steelhead. On 10 October 1974, the average size of juvenile steelhead electrofished in four main stem reaches was 10.2 cm FL (range, 5.1–18.8 cm FL; n = 125). The largest trout (21.3 cm FL) was found in the South Fork San Pedro Creek (K. R. Anderson, CDFG, unpubl. memo. of 28 October 1974). On 17 September 1976, the average size of juvenile steelhead electrofished in two main stem reaches was 8.9 cm FL (range, 3.3–17.3 cm FL; n = 26). Overall abundance of juvenile steelhead was apparently lower than in previous surveys (K. R. Anderson et al., CDFG. unpubl. memo. of 24 September 1976). Finally, on 15 November 1979, the mean size of juvenile steelhead electrofished in two main stem reaches was 9.4 cm FL (range, 5.6–16.8 cm FL; n = 43) (I. L. Paulsen and L. Fish, CDFG, unpubl. memo. of 21 November 1979). Estimated densities were 0.2 and 0.9 juvenile steelhead/m, which were much lower than those measured in 1973. Despite apparent differences in relative year-class strength, these four surveys demonstrated that the juvenile steelhead population in San Pedro Creek consistently comprised two age-classes, 0+ and 1+, and that the 0+ group dominated numerically. The relatively small proportion of 1+ trout present in any given survey indicates that the main smolting age of steelhead in San Pedro Creek is age 1. During the winter of 1975-76, entry of adults from the ocean and their migration to upstream spawning grounds were apparently restricted due to a lack of precipitation and thus reduced stream flow. Consequently, no adult steelhead or redds were observed in San Pedro Creek on 26 February 1976. Several adult steelhead, two estimated at 2.7 kg each, were observed in the creek on 1–2 March 1976, however. The local warden estimated that 60 adult steelhead had been poached at Adobe Road Bridge during this period (G. Scoppettone, CDFG, unpubl. memo of 25 March 1976 and 19 April 1976). In March 1978, about 600 steelhead died in San Pedro Creek due to the storm drain discharge of an unknown poison, possibly chlorinated swimming pool water (The Times, San Mateo, 22 June 1978). By 1985, the headwaters of San Pedro Creek were protected by virtue of their inclusion in San Pedro Valley County Park. In March 1985, 800 Dry Creek steelhead (8.8/kg) were stocked into the stream. When surveyed by the CDFG in May 1985 (J. Ford and L. Bordenave, DFG, unpubl. memo. of 29 July 1985), the creek system was in good condition overall. Steelhead spawning habitat was abundant in the upper main stem, or middle fork, but lacking in the north and south forks. Most spawning occurred within the park boundaries. Spawning reportedly occurred as late as May, and during the 1984–1985 spawning season, there were about 40 pairs of spawning steelhead within a 30 m spawning reach. Obstructions for upstream migrating spawners were identified, and storm drain pollution was still cited as a problem. Indeed, on 10 March 1987, 600–700 steelhead fry, yearlings, smolts, and adults were killed in the north fork and 2 km of the main stem as the result of a toxic storm drain discharge, probably chlorinated swimming pool water. The lowermost 880 m of San Pedro Creek was surveyed by the CDFG on 28 September 1988 (C. Dayes and D. Becker, CDFG, unpubl. memo. of 21 October 1988). Age 0+ and 1+ steelhead, up to about 20 cm in length, were observed throughout the reach, including the lagoon. Riffles provided over 464 m2 of spawning gravel for steelhead. Rearing habitat was good to excellent, and included abundant streamside riparian vegetation. Notably, the creek had continuous flow to the lagoon and contained two consecutive year-classes of juvenile steelhead, despite two consecutive drought years.