Fecundity and size at maturity of Palaemon longirostris (Decapoda, Palaemonidae) in the Mira River estuary (SW Portugal)

Abstract

Summary The reproductive traits of female Palaemon longirostris were examined in this study. The mean fecundity was 957±282 SD. The mean egg volume increased 17% from the early to the late development stage. By using the allometric model, no simple volumetric relationship was found between brood size and carapace length at any egg stage. For both early and late egg stages, a negative allometric level was obtained. During embryogenesis, egg loss was estimated at 5%, with no apparent effect on female size. Size at maturity was studied using morphometric analyses, assuming that the attainment of sexual maturity involves morphological changes of the pleura in order to form a brood chamber. A Mature 1 analysis evidenced overlapping “growth-phase” lines, suggesting that adult females may moult to a resting condition after breeding. The obtained regression lines indicate the presence of different morphotypes, but do not correspond to young and adult prawns. To determine size at maturity, a Mature 2 analysis was run for the young-like morphotype in an attempt to locate an intersection point delimiting the young and the adult growth phases. The estimated size closely matched the size of the smallest ovigerous prawn.