Captive Breeding of Endangered Yaqui Topminnow and Yaqui Chub for Recovery Purposes

Abstract

AbstractYaqui topminnow Poeciliopsis occidentalis sonoriensis and Yaqui chub Gila purpurea, two federally endangered fishes from the Rio Yaqui basin (Arizona, USA, and Sonora, Mexico), were propagated by various methods. Propagation of Yaqui topminnow was attempted in aquaria and wading pools; the greatest number of offspring was produced in 556‐L, plastic wading pools. We added substrate, artificial plants, and a vertical mesh barrier to create refuge for offspring. Fish were stocked when water was 19°C; after 1 month, when water temperatures exceeded 21°C, Yaqui topminnow started to produce young continuously. On average, 7.4 offspring/d were captured from four pools collectively. Yaqui chub were propagated in 189‐L, glass aquaria. We manipulated photoperiod, diet, and substrate to induce spawning of Yaqui chub, but success was only achieved after the water was chilled to 17°C for 30 d and then adjusted to 21°C over 14 d. After the water was maintained at 21°C for 3 d, we covered the bottom of each aquarium with glazed ceramic tiles and a raised plastic grid to protect eggs from predation. Broadcast spawning of Yaqui chub occurred at night; the next morning, we retrieved the tiles and the attached eggs and placed them in incubation tanks. Yaqui chub eggs hatched over the next 5 d, and the hatching success rate averaged 83%. After this initial spawn, manipulation of water temperature was not required to induce spawning, as Yaqui chub spawned each time tiles were placed in the tanks. These methods worked well, and we recommend them for propagation of Yaqui topminnow and Yaqui chub.