THE EFFECT OF GROUP INTERACTIONS ON THE DEVELOPMENT OF SIZE DISTRIBUTION IN MACROBRACHIUM ROSENBERGII (DE MAN) JUVENILE POPULATIONS

¹ Department of Environmental Biology, Life Science Institute, The Hebrew University of Jerusalem, Jerusalem, Israel

The distribution of body size among juvenile prawns, Macrobrachium rosenbergii (de Man), was assessed by comparing communally reared populations with singly raised individuals. Prawns reared in a group showed a relative excess of size variation, primarily associated with the appearance of two size classes which failed to appear among juveniles raised in isolation: 1) exceptionally fast-growing individuals, termed "jumpers," and 2) "laggards," which are generated in the presence of jumpers and represent a group of severely growth-repressed individuals. These results suggest that the variance of attained sizes of juveniles in a M. rosenbergii population is more affected by interactions within the prawn group than it is by genetic differences in growth potential of the individual prawns.