Evaluation of Substrate Type and Density as Factors in Optimizing Growth of Least Chub

Abstract

The least chub Iotichthys phlegethontis is a diminutive and rare cyprinid endemic to the Bonneville Basin of Utah. As part of a species recovery effort, aquaculture techniques were investigated. Three experiments are summarized here: two compared silt substrate and no substrate, and one evaluated the effect of three different densities on growth and survival. The substrate experiments were an attempt to compare extensive versus intensive culture. In the first test, growth of 4-7-month-old least chub in outdoor aquaria containing 2-3 cm of silt substrate was significantly higher than that of fish in indoor or outdoor aquaria with no substrate. Survival was unaffected by substrate treatment. In another test using fry that had just hatched, mortality rates were significantly higher in the aquaria treatment (mean 6 SD ¼ 95.3 6 2.3%) than in the silt substrate treatment (45.3 6 23.1%; P ¼ 0.009). Final length was also significantly higher in the simulated ponds (mean 6 SD ¼ 10.2 6 1.2 mm) than in the aquaria with no sediment (6.2 6 2.7 mm; P , 0.001). In a final, 8-week test, fish rearing densities of 2.27, 11.36, and 22.7 fish/L were compared among 5-6-week-old least chub. Growth and survival were not significantly affected within this range of rearing densities. These results indicate that extensive aquaculture using fertile fry ponds would produce more and faster-growing least chub than intensive raceways or tanks, assuming predation and disease were not factors. High rearing densities are also possible with this schooling species of cyprinid.

Conservation Aquaculture of Northern Leatherside Chub and Effects of Temperature on Egg Survival

“…We found no significant difference in growth or survival in the density range we examined. Our highest density, 3,400 fish/m 3 , was still well below or within previously recommended densities for other cyprinid species in intensive aquaculture (Hepher and Pruginin 1981;Horváth et al 1992;Wagner et al 2006), but the above densities were typically recommended for pond-reared cyprinids relying on natural foods (Stickney 1979;Horváth et al 1992;Feldlite and Milstein 2000).…”

“…Although the upper limit for juvenile northern leatherside chub rearing density has yet to be determined, densities of at least 3,400/m 3 can be used for intensive aquaculture without compromising growth and survival. As seen with the least chub Iotichthys phlegethontis (Wagner et al 2006), leatherside chub tend to be a schooling species; therefore, high densities are possible. The glass aquaria used for our study were adequate rearing environments for the densities we examined.…”

Culture of Plains Topminnow in a Pond Constructed for Species Conservation

“…Reintroduction is becoming an important tool in efforts to manage native fish (Archdeacon and Bonar 2009), creating a need to develop and maintain refuge populations as sources for rare fishes (Wagner et al 2006). Despite the potential importance of captive propagation to management and conservation actions (Schultz and Bonar 2009), little is known about culture for most threatened or endangered fishes, especially compared with sport and baitfish species (Kline and Bonar 2009).…”