Spatial and Temporal Variation in Abundance and Biomass of Different Sex Classes of the Estuary Prawn Macrobrachium equidens (Dana, 1852) (Decapoda, Palaemonidae) From the Mekong Estuaries, With Notes on Its Salinity Tolerance

The estuarine prawn Macrobrachium equidens is among the most frequently exploited fishery resources in the Mekong estuaries, primarily harvested by artisanal fisheries to supply local markets. Despite its ecological and economic importance, the reproductive biology of the species remains poorly understood. This study aimed to investigate the spatio-temporal variation in the abundance and biomass of different sex classes of M. equidens across four Mekong estuaries in Southern Vietnam. Samples were collected using a beam trawl at four estuarine locations (Cua Dai, Ham Luong, Ba Lai, and Co Chien) over four sampling periods from March to November 2022. The findings revealed minimal seasonal and spatial variation in the total abundance and biomass of male and female M. equidens. However, significant fluctuations were observed in the proportions of non-ovigerous females (%NOF) and ovigerous females (%OF). Spearman analysis showed a positive correlation between %NOF and salinity, while %OF showed a negative correlation with salinity, suggesting that salinity played a key role in regulating the proportions of non-ovigerous and ovigerous females of M. equidens in Mekong estuaries. The study also showed that the period of highest production of M. equidens in the Mekong estuaries appears to coincide with the peak of the rainy season, from August to November. This research provides important insights into the reproductive biology of estuarine prawn, enhancing our understanding of their adaptive approaches and reproductive capabilities in relation to environmental conditions.