6043

• UCREFRP Catalog Number: 6043
• Author: Desert Fishes Council ‎(Edwin Pister, e.
• Title: A Summary of the Proceeding of the Tenth Annual Symposium.
• USFW Year: 1978.
• USFW - Doc Type: November 16-18, 1978.
• Copyright Material: NO

51
POPULATION DYNAMICS OF CYPRINODON RADIOSUS: A PRELIMINARY
REPORT.
David K. Young, California State University, Fresno.
The Owens pupfish, Cyprinodon radiosus, is a member of a
limited desert fish fauna whose existence has been sustained by
the efforts of various government and private agencies, as well
as several committed individuals. In 1964, the actions of
Dr. C. Hubbs, Dr. R. Miller, and Mr. Phil Pister resulted in
rediscovering a remnant population of this once thought extinct
species. Since then the Owens pupfish has been the subject of
an intense preservation program. In 1968, it was listed as
endangered by the U.S. ;Department of Interior.
Historically, the distribution of C. radiosus was restricted
to the Owens Valley drainage, from near Lone Pine in Inyo County,
Ca., in the south, to Fish Slough in Mono County, Ca., in the
north. Today, the Owens pupfish is limited to three sanctuaries.
One refugium is found at Warm Spring near Big Pine, Inyo County.
The other two sanctuaries, the Owens Valley Native Fish Sanctuary
and the BLM Spring Sanctuary, are located at Fish Slough.
I visited these refuges in July and August, 1976, with
Professor Robert Brown (C.S.U.F.). It was during one of these
visits to the BLM Spring Sanctuary that I noticed that a gravel
barrier, originally constructed to prevent upstream movement of
predatory fish into the sanctuary, had been destroyed. We
searched the stream between the two dams but failed to find
pupfish. By using electrofishing gear we were able to obtain a
population index of ten largemouth bass (Micropterus salmoides).
The stream section north of the upstream dam appeared to be free
of bass and here we observed many pupfish and mosquitofish
(Gambusia affinis). I brought these findings to the attention of
Phil Pister who suggested that I pursue the following objectives:
1. To eradicate the existing population of largemouth bass,
repair the gravel dam and reintroduce Cyprinodon radiosus
into its native habitat.
2. To study the population dynamics of the Owens pupfish
and to monitor the growth characteristics of this
species, as well as the ecological consequences of this
growth.
3. To observe and record the behavioral patterns of C.
radiosus in the field.
4. To describe the distribution of this species in relation
to spring inflow, vegetation types, water quality, and
temperatures.
5. To develop recommendations for effective management.
Work began in March, 1977, by chemically treating the stream
and repairing the gravel percolator dam. This resulted in the