following salmonid evolutionary significant units2 (ESUs) (NOAA Fisheries 2005a) have the potential to be near the project site.

Central California coast steelhead trout (Oncorhynchus mykiss) Federally Threatened, California Species of Special Concern. Steelhead populations in what is known as the Central California Coast “evolutionarily significant unit” are listed as threatened under the Federal Endangered Species Act (FESA). Anadromous rainbow trout, or steelhead, occur in California from the Smith River in Del Norte County south along the coast to San Mateo Creek, San Diego County, and in streams of the San Francisco Estuary and Central Valley (Moyle, 2002).

All Central Valley steelhead are considered winter steelhead. Busby et al. (1996) wrote, “Steelhead within this ESU have the longest freshwater migration of any population of winter steelhead. There is essentially a single continuous run of steelhead in the upper Sacramento River. River entry ranges from July through May, with peaks in September and February; spawning begins in late December and can extend into April.”

The timing of steelhead outmigration is less well known, but trawl capture data are consistent with a late-winter and spring migration (Jahn 2011a). Steelhead smolts, like chinook smolts, migrate mainly in deep water, but steelhead tend to wander into shallow water more than chinook (Jahn 2011a). Thus, there is some chance that steelhead, especially of the coastal ESU that spawn in some south Bay tributaries, may enter the Brisbane Lagoon in small numbers. Because numbers are low, and most smolts are expected to remain in the deep channel, the probability of encounter within the lagoon at any given time would be low.

The “headwaters” of Visitacion Creek terminate in the former railyard area to the east of the round house and consist of shallow stagnant drainages which are dry during approximately half of the year. The drainage channels in this vicinity are not suitable for spawning steelhead due to the lack of appropriate spawning substrates and absence of sufficient attracting water flows for steelhead.

Spawning habitat for anadromous fish does not exist within Brisbane Lagoon or within the tributary channels to the lagoon. Guadelupe Creek does not provide spawning habitat because it is located underground within culverts for significant portions of its length to the west of the outfall at the northwest corner of the lagoon. The unnamed drainage that enters the southern corner of the lagoon likewise runs through underground storm

² Evolutionary significant unit (ESU) refers to a population of organisms that is considered to be distinct from other populations for purposes of conservation.