CREAR and HAVDOCK: REARING DESERT PUPFISH 



ment of Fish and Game and judged that the 

 numbers of mosquitofish, Gambnsia affhiis, and 

 desert pupfish were sufficient to support a large 

 population of carnivorous game fish. Cowles 

 (1934) reported the pupfish populations to be 

 exceedingly large in and around the Salton Sea. 

 In 1956 Barlow (1961) observed schools of ju- 

 venile pupfish of nearly 10,000 individuals. He 

 estimated that one large, isolated, shore pool 

 at the Salton Sea contained 150 adults per square 

 meter. Today, in the Salton Sea area desert 

 pupfish are almost totally confined to a few trib- 

 utaries. In response to the severe reduction of 

 pupfish populations in the Salton Sea area, Jack 

 Hesemeyer, Supervisor of the Anza-Borrego 

 State Park, has built a pupfish sanctuary near 

 the Park headquarters at Borrego Springs. This 

 small sanctuary was stocked on June 24, 1970, 

 with 48 laboratory-reared fish produced by the 

 techniques outlined below. Several hundred 

 additional fish were placed in the Palm Canyon 

 pools nearby. 



The authors hope that this article, in addition 

 to demonstrating the value of the desert pup- 

 fish as a teaching and research animal, will help 

 in its preservation by describing laboratory- 

 spawning methods that can provide adequate 

 stocks for sanctuaries in natural and artificial 

 habitats. In addition, the rearing techniques 

 described here for desert pupfish may be useful 

 for the preservation of many other species of 

 pupfish that are in danger of extinction. 



MATERIALS AND METHODS 



The desert pupfish used to develop spawning 

 techniques were seined from an irrigation ditch 

 emptying on the northwestern shore of the 

 Salton Sea in Riverside County, Calif. Speci- 

 mens were transported in plastic garbage pails 

 filled with aerated ditch water to the Fishery- 

 Oceanography Center at La JoUa, Calif. We 

 found that the water temperature during trans- 

 port should not be allowed to fluctuate radically 

 from that at which the fish are found. 



Many of the specimens collected were infected 

 by a freshwater parasitic copepod of the family 

 Lernaeidae (possibly introduced with home- 

 aquarium fish). The large egg cases of this 



copepod were clearly visible on the fish, usually 

 at the base of the fins. Individuals carrying 

 this parasite were weak and commonly died dur- 

 ing or soon after transport. Reichenbach-Klinke 

 and Elkan (1965) recommend a salt bath (NaCl, 

 0.76-1.1'^r) to eliminate such copepods. To 

 treat this infection, all fish on arrival at the 

 laboratory were converted to seawater over a 

 5-day period. Kinne (1960) reported that a 1- 

 month-old pupfish can survive sudden salinity 

 changes up to 35 '/ic, whereas 1-year-old adults 

 cannot survive sudden salinity changes of more 

 than 10 to 15 7^. Robert R. Miller (1970, per- 

 sonal communication), however, reports that in 

 1937 he found that this species could be shifted 

 with ease directly from fresh water to seawater 

 and back. After conversion to seawater all 

 traces of the parasitic copepod vanished. To- 

 ward the end of the experiment, several fish 

 died from a devastating protozoan infection in 

 the epithelial tissue surrounding the mouth. 

 The tissue appeared bloody and often had com- 

 pletely disintegrated. Many apparently healthy 

 fish died with little or no warning in less than 

 12 hr. The marine parasitic protozoan, Cryp- 

 tocaryon irritans, prevalent in the Scripps water 

 system was suspected ( Wilkie and Gordin, 1969) . 

 The surviving fish were transferred back to fresh 

 water and, fortunately, the parasite failed to 

 make the transition. 



LABORATORY CONDITIONS 



The fish were maintained in 20-gal tanks with 

 subsurface filters covered with crushed oyster 

 shell. The water was changed completely and 

 the shell washed approximately every 6 weeks. 

 Four individuals were isolated in each aquarium 

 by plastic, perforated dividers. The tanks were 

 maintained at room temperature, 20° to 22° C. 

 Standard aquarium heaters were used whenever 

 higher temperatures were needed. No attempt 

 was made to control pH other than the use of 

 the crushed oyster shell substrate. 



The fish were fed frozen adult brine shrimp, 

 Artemia salina, three times daily during the 

 week and once a day on weekends. Kinne (1960) 

 and Kinne and Kinne (1962) used two species of 



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