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FISHES OF THE SANTA CLARA RIVER SYSTEM,

SOUTHERN CA.LIFORNIA 1

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By MICHAEL A. BELL

ABSTRACT: The distribution of fishes within the Santa Clara River and most of

its tributaries in which fishes were found is described fron1 field observations and 46

fish collections. Fifteen species of fishes were collected, of which five probably are

native to the system. All native species are peripheral freshwater fishes so there is

no evidence of fauna] exchange with adjacent river systems. Gasterosteus aculeatus

and Gila orcutti occurred at almost all collecting stations while five species occurred

at only one. This river system contains a high diversity of freshwater fishes for south-

ern California streams. The Santa Clara River system is vulnerable to habitat destruc-

tion by urbanization, and potential threats to fishes of the system are discussed.

INTRODUCTION

Although many papers have discussed individual fish species from the Santa

Clara River system (Girard 1854; Hubbs 1967; Hubbs, Hubbs and Johnson 1943;

Miller 1960, 1968, 1972, 1973; Ross 1973; Smith 1966), its fish fauna has not been

described previously. By virtue of its proximity to Los Angeles, this drainage currently

is subject to rapid urbanization with the attendant dangers of habitat destruction and

pollution. The only known native population of the endangered unarmored threespine

stickleback, Gasterosteus aculeatus williamsoni (Girard), still survives in this drain-

age. This drainage also harbors some introduced fishes endemic to southern California

and some species of game fishes. Thus, it is desirable to describe t11e fish fauna before

disturbance of the ecosystem causes the elimination of some species. This description

will serve in the future as a base line to assess the impact of urbanization on the fish

fauna.

MATERIALS AND METHODS

Forty-six fish collections were made at varying intervals from the mouth of the

Santa Clara River system to as far upstream as water existed except in Piru and Santa

Paula creeks primarily between September 4 and November 9, 1975 (Fig. l). Col-

lections were made in the Santa Clara River, Todd Barranca, Sespe Creek, Piru Creek

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REVIEW COMMITTEE FOR THIS CONTRIBUTION

ROBERT J. LA VEN BERG

J. D. MCPHAIL

ROBERT R. MILLER

CAMM C. SWIFT

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Research Associate in Ichthyology, Natural History Museum of Los Angeles County, and Depart-

ment of Biology, University of California, Los Angeles, California 90024.