Growth, size rank, and maturation of the freshwater prawn, Macrobrachium rosenbergii: analysis of marked prawns in an experimental population

Small immature female Malaysian giant freshwater prawns had high growth rates. Growth of female prawns nearly ceased after maturation. This compensatory growth process produces adult females having a unimodal, symmetrical size distribution with a mean above the size threshold for maturation (c18-26 g). The small male morphotype has a low growth rate, while the orange claw male morphotype has a high growth rate. As the orange claw males transform to the blue claw morphotype, growth ceases. Examination of changes in size rank during the maturation process supported the leapfrog phenomenon. The fastest growing, largest orange claw male is the first to metamorphose to the blue claw morphotype (at a size of 35 g). As other orange claw males exceed this size, they transform in a sequential process so that the most recent blue claw male is generally the largest blue claw male in the population. Thus, growth of males is depensatory throughout the process of morphotypic differentiation, leading to a wide size range of orange and blue claw males. The leapfrog phenomenon is discussed in terms of the reproductive success of the blue claw males. Regarding aquaculture, the stimulatory effect on the remaining prawns of selectively harvesting the largest blue claw and orange claw prawns suggests that the inclusion of a small proportion of large "target' blue claw males might stimulate rapid growth of orange claw males in a population of smaller prawns. -from Authors