Distribution and ecology of stream fishes in the San Francisco Bay drainage.

Abstract

Of 35 species collected, 22 (63%) were exotic to California and 13 (37%) were native. Urbanization has resulted in the alternation and destruction of many stream habitats, and in changes in the dominance of fish assemblages from native to introduced species. The native Rhinichthys osculus, Eucyclogobius newberryi, Pogonichthys macrolepidotus and Gila crassicauda are apparently extinct in study area streams. Oncorhynchus kisutch, Mylopharodon conocephalus, Hysterocarpus traskii and Archoplites interruptus have experienced significant reductions in their ranges. The abundance of native fishes was positively correlated with occurrence of other native species primarily in stream habitats with little human disturbance. Abundance of introduced fishes shows a significant negative correlation with occurrence of native species. Introduced fishes occurred primarily in large, highly disturbed pools at low and intermediate elevations, often in channelized stream sections.- from Author