Methods for Spawning Yaqui Chub and Yaqui Topminnow
September 2002 to December 2007
Development of methods to spawn and rear threatened and endangered fish is necessary for their conservation. We report methods to propagate and rear Yaqui chub and Yaqui topminnow, two endangered fishes from the Rio Yaqui basin of northern Sonora, Mexico and southeastern Arizona, USA. We held mature Yaqui topminnow (2 males and 6 females) in 556-L plastic wading pools housed in a greenhouse with an evaporative cooler. We added cobble, gravel, and artificial plants to pools and installed a vertical mesh barrier impassible to larger fish to create refuge for offspring. Water in pools increased from 19°C as the ambient temperature increased. Yaqui topminnow produced young after 1 month when the temperature exceeded 21°C. Numbers of offspring were variable but reproduction was continuous after the temperature exceeded 21°C. On average, 7.4 offspring were captured each day from the four pools collectively. We spawned Yaqui chub in four 189-L glass aquaria stocked with 6-9 fish per tank. We chilled water to 17°C for 30 d and then increased the temperature to 21°C over 14 d. After the temperature was 21°C for 3 d, we covered the bottom of aquaria with glazed ceramic tiles and a raised plastic grid over the tiles to protect eggs from predation. We found Yaqui chub to be broadcast spawners. They spawned at night, and we retrieved tiles containing eggs the following morning and placed them in incubation tanks. Yaqui chub eggs hatched in the next 5 d with a success rate of 83%. Both methods worked well and we recommend them to propagate these species. The student graduated spring 2007, and this work was published in January 2009 in the North American Journal of Aquaculture.