Reproductive Biology and Spawning Patterns of Polynemus melanochir: Implications for Conservation and Population Management

Understanding the reproductive biology of Polynemus melanochir is essential for conservation purposes and a sustainable management perspective for this species in the Mekong River system. The current study investigates patterns of ovarian histology in this species along with spawning season, fecundity, and maturity stages in female specimens caught in the Hau River. The study was carried out from March 2024 to February 2025, providing insights into the species’ reproductive biology and its ecological implications. Specimens were caught with various fishing gears (trawl net and gill net) and ranged in size from 10.8 to 27.5 cm (18.8 ± 0.2 SE), while their weights varied between 8.05 and 132.37 g (45.06 ± 1.76 SE). Macroscopic observation of gonads enhanced by histological analysis enabled us to identify five stages of ovarian maturation, offering valuable information for population monitoring. The gonadosomatic index (GSI) and frequency of maturity stages indicated that reproductive activity was at its highest level in March, which was symbolized by a peak for GSI (GSI = 3.74 ± 0.89), as spawning likely occurred from December to April. Absolute fecundity ranged from 2,726 to 647,306 eggs per female (252,853 ± 41,185 SE), while relative fecundity averaged 2,696 ± 376 SE eggs per gram of body weight. Fecundity exhibited a strong correlation with total length (r2 = 0.70) and body weight (r2 = 0.72), highlighting possible size-based reproductive patterns. The estimated first maturity size was 16.98 ± 0.23 SE cm, suggesting the need for size-selective conservation measures. These findings certainly add knowledge to our understanding of the reproductive biology of P. melanochir as they contribute to its conservation and management perspectives within the Mekong Delta. Future research should, however, explore habitat preferences and environmental influences on reproductive success to support biodiversity conservation efforts.