Abstract

Growth patterns were examined in newly-hatched juvenile Australian crayfish, Cherax quadricarinatus, during nutrient deprivation and recovery. During a ten week culture period, crayfish were fed feeds known to elicit high, medium, or low growth rates (HGRD, MGRD, and LGRD, respectively). After ten weeks, crayfish fed HGRD exhibited the shortest mean molt interval (time between successive molts), the greatest mean molt increment (weight gain per molt), and had the highest mean weight gain. Crayfish fed MGRD exhibited a mean molt interval similar in duration to that of crayfish fed HGRD, but initially had a reduced mean molt increment when compared to the HGRD treatment. Crayfish fed LGRD initially had the longest mean molt interval and the smallest mean molt increment. Although crayfish fed LGRD and MGRD later demonstrated a similar mean molt interval and molt increment as that of crayfish fed HGRD, at the end of ten weeks crayfish fed MGRD were approximately one-half the mean weight of crayfish fed HGRD and crayfish fed LGRD were approximately one­fifth the mean weight of crayfish fed HGRD. After ten weeks, the surviving individuals in the MGRD and LGRD treatments were fed HGRD. The mean molt interval for the MGRD/HGRD treatment during this period was similar in duration to that of same-size class crayfish in the HGRD/HGRD treatment. Mean molt increment for the MGRD/ HGRD treatment was also similar to that for same-size class crayfish in the HGRD/ HGRD treatment. Mean molt interval for the LGRD/HGRD treatment during this period was shorter in duration and mean molt increment greater than that observed for same­size crayfish in the HGRD/HGRD treatment. Overall, crayfish that exhibited minimal weight gain when cultured initially using poor-quality feeds (LGRD and MGRD) exhibited improved weight gain when converted to a high-quality feed (HGRD). The ability of Cherax to respond to high-quality feeds following nutritional stress may have management implications for intensive culture. Specifically, short-term nutrient deprivation may not have long term consequences resulting in stunted populations, particularly if nutrients are proffered to crayfish at a later time.

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