Propagation of hybrid Devils Hole Pupfish × Ash Meadows Amargosa Pupfish

Recent censuses of Devils Hole Pupfish Cyprinodon diabolis revealed that fewer than 100 individuals currently remain in the wild. Captive propagation is among actions being considered to prevent their extinction, but no pure-strain Devils Hole Pupfish were available for broodstock. To help provide emergency information, we investigated techniques to propagate their most closely related relative, hybrid Devils Hole Pupfish C. diabolis× Ash Meadows Amargosa Pupfish C. nevadensis mionectes. We tested various temperatures and larval feeds with respect to egg production, larval survival, and growth. Larval survival and growth were similar from 24°C to 32°C and egg production peaked at static 28°C; however, reducing water temperatures to 23°C and then raising them to 28°C resulted in even higher production. Larvae fed infusoria, Rio Grande Silvery Minnow Chow (RGSM), or Zeigler larval diet (ZLD) had the highest survival (79.4, 71.6, and 73.4%, respectively), and those fed Otohime (OTO) had the lowest survival (60.8%), although OTO provided greatest (14 mm) 30-d growth. Supplementation of RGSM or ZLD with Artemia nauplii increased growth but decreased survival. Larval production was maximized by placing six spawning mops, constructed of yarn and tile, in each of four 437-L parental aquaria, stocked with 24 adult fish each (1:1 sex ratio) for 3 d, to attract adults and provide spawning substrate. A 30% water change conducted on the same day of mop placement lowered water temperature from 28°C to 23°C. Water temperature was raised back to 28°C over 48 h. After 3 d, mops were transferred to hatching aquaria that were held at 28°C and aerated until larval hatch. Although some differences likely exist in effective propagation techniques for hybrid and pure-strain Devils Hole Pupfish, these data help provide initial recommendations to aid recovery.