CREAR and HAVEWCK: REARING DESERT PUPFISH 



lasts from 30 min to 2 hr, depending on the 

 size of the female and the number of eggs laid. 

 In order to prevent the serious injury or death 

 of the female, the male was not left in the spawn- 

 ing bin for longer than 2 hr. After termination 

 of spawning the fish were returned to their 

 aquaria and the feces were removed from the 

 container. The spawning bin was then sus- 

 pended in a 27° C water bath with aeration. 

 Kinne and Kinne's (1962) data on hatching 

 shows that any incubation temperature between 

 24° and 30° C should produce hatches of at least 

 80 Sf in 100 '~r air-saturated seawater. Pup- 

 fish eggs left at room temperature in the lab- 

 oratory at La Jolla suffered extremely high mor- 

 talities owing to daily temperature fluctuations 

 between 18° and 24° C. Kinne and Kinne (1962) 

 supplied data on egg mortalities and incubation 

 periods at different temperatures from 10° to 

 37° C. 



Hatching success of different breeding pairs 

 varied unexplainably under constant conditions. 

 A large sample of eggs from one breeding pair 

 showed, however, that salinity and temperature 

 markedly effected the hatching success of pup- 

 fish eggs (Table 2). Eggs in small clusters, 

 apparently laid at nearly the same instant, sel- 

 dom hatched. Kinne and Kinne (1962) also 

 reported reduced development and increased 

 mortalities for conglomerated eggs. 



Pupfish larvae are large enough (5.5 mm total 

 length at 27° C in 50 9 seawater) to feed from 

 the day of hatching on brine shrimp nauplii 

 (Salt Lake variety), Artemia salina. The 

 larvae when handled were drawn with a bulb 

 into a long glass tube. Kinne and Kinne (1962) 

 gave extensive data on the growth, food intake, 



Table 2. — Hatching success of desert pupfish eggs. 



and food conversion for pupfish larvae at dif- 

 ferent temperatures and salinities. 



CONCLUSIONS 



The desert pupfish may be reared in the lab- 

 oratory over a wide range of temperatures and 

 salinities. Half-strength seawater at 27° C pro- 

 vided the best hatch observed during this study. 

 The pupfish is a hardy laboratory animal that 

 does well in captivity if proper attention is paid 

 to food, space, and hygiene. However, a note 

 of caution should be added, since we reared only 

 two generations of pupfish. Bunnell (1970) 

 states that when a pupfish stock is bred in cap- 

 tivity from a single pair, the fish do well at first, 

 but gradually die out over several generations. 

 This possibility should be further substantiated 

 before committing experimental studies to a 

 single line of descent. 



The authors believe that the desert pupfish is 

 an excellent experimental animal for many types 

 of biological research. Studies of the syste- 

 matics (Miller, 1948) , behavior (Barlow, 1961), 

 and physiology (e.g., Kinne and Kinne, 1962) 

 provide a wealth of background information on 

 the basic biology of pupfish which will prove 

 valuable to investigators interested in using this 

 species in teaching and research. Other reports 

 (e.g., Bunnell, 1970) indicate the critical status 

 of some species of Cyprinodon, including C. 

 macularius, and point out the need to provide 

 sanctuaries to avoid extinction of this unique 

 species. Laboratory rearing of pupfish will not 

 only provide material for scientific observation 

 and experimentation, but will also remove some 

 of the pressure on an already rapidly contracting 

 natural population by providing adequate stocks 

 for present and future sanctuaries. Both 

 measures should enhance the value of the desert 

 pupfish and emphasize the importance of saving 

 the species from extinction. 



ACKNOWLEDGMENTS 



The authors wish to extend their deep appre- 

 ciation to Robert Rush Miller and Carl Hubbs 

 for their valuable suggestions and extensive 

 editing of this manuscript. 



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