Thomas M. Baugh

Abstract.-The Salt Creek pupfish, -Cyprinodon salinus-, is adapted to fresh water in aquaria.

The Salt Creek pupfish, -Cyprinodon salinus- is endemic to Salt Creek, a short, 2 km, spring-fed stream located at about 70 m below sea level on the floor of Death Valley, Inyo County, California. Although this cyprinodont was first described by Miller (1943), it appears only infrequently in the subsequent literature (Burley 1978, Brown and Feldmeth 1971, Hunt 1975, LaBounty and Deacon 1972, Miller 1948, Miller 1968, Soltz and Naiman 1978).

To obtain specimens for a study of social behavior, twelve -C. salinus were taken from Salt Creek on 30 September 1980. The fish, which ranged in size from 15 to 35 mm,were cap- tured with dip nets from open waters on the banks of the first small pool below McLean Spring and from a mud-detritus substrate at the same pool. Water temperature at the time of capture was 17.8 C, and salinity of the water was 20 o/oo. The fish were placed in stream water in a 7.6 liter plastic bucket and transported by backpack, automobile, and airline to the laboratory, where they were placed in a 75 liter aquarium on 2 October 1980.

The water in the aquarium consisted of aged (21 days) tap- water to which had been added enough Instant Ocean(r) synthetic salts to bring the salinity to 20.6 o/oo. The fish accepted a mixed diet of TetraMin Staple Food(r), Tetra Krillflakes(r), and Tetra AlgaeFlakes(r) at 0600 and San Francisco Bay Brand(r) frozen brine shrimp at 1630.

To circumvent problems associated with maintaining fish in saline aquarium environments, I decided to desalinate -C. salinus- and conduct behavioral observations in a freshwater environment. Steunkel and Hillyard (1978) reported maintain- ing this species in freshwater but gave no details or sched- ule for desalination.

Desalination began on 4 October by the removal of saline aquarium water and the addition of an equal amount of aged (7 days) tapwater. During the desalination sequence, starting from a salinity of 20.6 o/oo, daily salinity was as follows: 17.8, 15.3, 12.7, 10.1, 7.5, 4.8, and 3.4. Throughout this schedule the water temperature was maintain- ed at 20 C.

After six months the fish have shown no adverse effects to the adaptive procedure. In addition, they have spawned repeatedly in this freshwater environment.

Acknowledgments

I thank George Van derLippe, superintendent, and Peter G. Sanchez, resource specialist, Death Valley National Monument for their help in various phases of my work with this species.

Literature Cited

Brown, J. H. and C. R. Feldmeth. 1979. Evolution in constant and fluctuating environments: thermal tolerance of the desert pupfish (Cyprinodon). Evolution 25(2):390-398

Burley, V. J. 1978. Salt Creek nature trail. Death Valley Nat. Hist. Assoc., California. 15 pp.

Hunt, C. B. 1975. Death Valley: geology, ecology, archaeology. Univ. of Calif. Press, Las Angeles. 234 pp

LaBounty, J. F., and J. E. Deacon. 1972. -Cyprinodon milleri-, a new species of pupfish (family Cyprinidontidae) from Death Valley, California. Copeia 1972(4):769-780

Miller, R. R. 1943. -Cyprinodon salinus-, a new species of fish from Death Valley, California. Copeia 1943:69-78.

---.1948. pages 86-87 in The cyprinodont fishes of the Death Valley system of eastern California and southwestern Nevada. Museum Zool., Univ. of Mich. Misc. Publ. No. 68, Ann Arbor.

---.1968. Records of some native freshwater fishes trans- planted into various waters of California, Baja California, and Nevada. Calif. Fish and Game 54(3):170-179.

Soltz, D. L., and R. J. Naiman. 1978. The natural history of native fishes in the Death Valley system. Natl. Hist. Museum, Los Angeles County Sci. Ser. 30. 76pp.

Steunkel, E. L., and S. D. Hillyard. 1978. Page 49 in Effects of temperature and salinity on electrolyte and energy metabolism in the pupfish, -Cyprinodon salinus. Proc. 10th Ann. Symp. Desert Fish. Coun.