Effects of temperature and salinity on weight gain, oxygen consumption rate, and growth efficiency in juvenile red-claw crayfish Cherax quadricarinatus

Weight gain and metabolic rates, as determined by oxygen consumption rates, were examined in Juvenile Australian red-claw crayfish Cherax quadricarinatus exposed to different temperatures 16-32 C in 2 C increments) or salinities (0-30 ppt in 5 ppt increments). Mean weight gain, ruching frequency. and survival (%) were dependent on temperature and salinity. In freshwater (0 ppt), maximal weight gain and molting frequency were observed at 28 C with maximal survival observed over the temperature range of 24-30 C. Metabolic rates in freshwater were temperature dependent (mean Q(10) = 2.44). Maximal weight gain and molting frequency were observed at salinities of 0 and 5 ppt (28 C) however, survival was reduced at salinities greater than or equal to 5 ppt. Metabolic rates were not salinity dependent and did not differ significantly over the salinity range from 0-20 ppt. Growth efficiencies, calculated by dividing weight,am by total metabolic energy expenditure (i.e., weight gain + metabolic rate), were highest at a temperature of 20 C (0 ppt) and Lit salinities of 0 and 5 ppt (28 C). These data suggest that, Lit higher Culture temperatures, maximal weight gain of red-claw juveniles may be reduced when food resources are limited. Maximal weight gain. at optimal temperatures (28 C) with unlimited food supply, does not appear to be effected by low salinity conditions. Because of the potential commercial value of red-claw, culturists should be aware of the relationship between environmental condition and metabolic energy requirements to ensure maximal weight gain and survival Of juveniles.