The present study did not represent typical nursery conditions. Nevertheless, it is
clear from the results that an adequate ration is of major importance in this phase. The
initial density of juvenile crayfish in the aquaria was close to 500 m-*, half of that
reported by Jones (1990) for nursery conditions. Despite the relatively low density, the
high quality of food, and the provision of shelters, even in the groups that received food
daily (ad libitum) there was a substantial reduction in survival after less than a month.
We suppose that this stemmed mainly from the cannibalistic nature of the crayfish.
Further studies are needed aimed at gaining a better control of this phenomenon.