Lethal temperatures for Rhamdia quelen larvae (Pimelodidae)

Abstract

The lower and upper lethal temperatures (LT50) of R. quelen larvae were determined. The larvae were obtained from two spawning periods with hatching temperatures of 21 and 26ºC respectively. Larvae were placed in tanks at which the temperatures were either increased 1ºC every 15min, or reduced 1ºC every 20min until larval movement ceased. This temperature was then maintained for 96h. Minimum mortality (29.0 ± 1.5%) was observed in the larvae held at hatching temperatures. The lower LT50 were 15.01 and 16.72ºC, and the upper LT50 were 29.25 and 27.83ºC for the larvae hatching at 21 and 26ºC, respectively. Thus, apparently there is no difference with relation to temperature change tolerance between larvae hatched in both temperatures.