Reproductive Dynamics, Performance, and Energy Allocation Strategies in the Freshwater Prawn Palaemon argentinus

Reproduction is an energetically demanding process requiring trade-offs between somatic growth, maintenance, and reproductive investment. This study aimed to investigate the reproductive biology and energy management of the freshwater prawn Palaemon argentinus in its natural habitat. We thus analyzed the population dynamics, reproductive performance (fecundity, egg size, and reproductive output), and female energy allocation strategies (capital or income) during ovarian development by examining the relationship between the hepatosomatic index and the gonadosomatic index. We also compared gonadosomatic index values and oocyte size between nonovigerous and ovigerous females to assess whether ovarian maturation energetically competes with embryo care. Our results showed that the reproductive season of P. argentinus is restricted to spring and summer, with a pronounced first peak in early spring, dominated by large older females with high fecundity, followed by a decline in spawning activity of this group, and a subsequent smaller peak toward the end of the reproductive season, driven by younger females. Egg size and reproductive output did not vary across the reproductive season. Females used mixed energy allocation strategies that shifted dynamically across ovarian maturation. During the incipient stage of ovarian development, energy is simultaneously stored in both the hepatopancreas and the ovary. At the middle developing stage, females predominantly rely on an income breeding strategy, whereas at the final stage of ovarian maturation, they shift to a capital breeding strategy. Finally, ovigerous females exhibited lower gonadosomatic index values and smaller oocytes than nonovigerous females, suggesting that energy allocated to embryo incubation constrains the resources available for ovarian rematuration.