Effect of water temperature in the early life phases and on the sexual proportion of Rhamdia quelen

Abstract

The development of jundiás Rhamdia quelen subjected to different temperatures (19, 24 and 29^oC) in the phases of fertilization, hatching and larval rearing (Phase 1) were evaluated; in the Phase of nursery (phase 2), the sex ratio of fish when kept at constant temperature were determined. In Phase 1, the survival, weight and total length were evaluated and, during the hatchery, 7-L plastic tanks stocked with 20 larvae L^-1 were used as experimental units. Phase 2 used 60 fingerlings stocked in 80-L circular tanks connected to a recirculating water system. Monthly, the survival, weight, total length, feed consumption, feed conversion rate (FCR) and specific growth rate (SGR) were measured, and also the sex ratio of fingerlings at the end of the experiment. Survival was lower (P<0.05) in colder temperature during Phase 1 and remained the same at the end of Phase 2. No influence of temperature was registered on the final weight of animals (P>0.05) in both phases, but total length for larvae and for fingerlings reared on colder temperature were lower at the end of Phase 1 (19°C: 1.78 ± 0.39 cm; 24°C: 2.32 ± 0.33 cm; 29°C: 2.49 ± 0.56 cm) and Phase 2 (19°C: 7.42 ± 0.91 cm; 24°C: 8.28 ± 0.96 cm; 29°C: 8.56 ± 0.95 cm), respectively, while consumption, FCR and SGR showed better response with temperature increase. The number of males produced was higher than that of females, but the sex ratio was not affected by the temperature.