In recent years in Israel, there has been an increasing trend of intensification of tilapia
culture in closed systems because of constraints on water consumption ŽMires and
Anjioni, 1997.. We have recently investigated the possibility of integrating the redclaw
crayfish, Cherax quadricarinatus, in such systems in order to increase the total
production ŽKarplus et al., unpublished data.. The results revealed no negative effects of
crayfish on the growth of fish. Since the crayfish are to be added to existing tilapia
culture systems in which tilapia would be the primary species, this result was encouraging.
Moreover, the fish grew better with crayfish than in fish monoculture. A possible
explanation could be that the fish were competitively superior over the crayfish and
consequently consumed some of the feed ration intended for the crayfish. In a recent
behavioural study of food competition in small groups, we found that the competitive
advantage of red tilapia depended on their size relative to the crayfish ŽBarki and
Karplus, unpublished data..
In the present study, we attempted to find an appropriate feeding