Prawn community structure in the subtropical Mfolozi–Msunduzi estuarine system, KwaZulu-Natal, South Africa

Abstract

The life cycles of many marine and freshwater prawn species are closely associated with estuarine habitat. Here, the prawn community of the Mfolozi-Msunduzi estuarine system is described and the system's potential as an alternative nursery for prawns during prolonged closure of the adjacent St Lucia estuarine system is examined. Sampling was conducted at five localities in summer and winter in 2007-2012. The Mfolozi-Msunduzi Estuary is a river-dominated system with mouth condition, sediment grain size and turbidity being the most important factors affecting the structure of its prawn community. Twelve prawn species were recorded, including five marine penaeid and five freshwater palaemonid species. The prawn community was numerically dominated by freshwater Macrobrachium equidens and two penaeids, Fenneropenaeus indicus and Metapenaeus monoceros. Significant differences were recorded between summer and winter samples, with freshwater species dominating the catch in summer, while penaeid species were dominant in winter. The marked seasonal change in the prawn community was related to strong river flows during summer creating low-salinity conditions, unsuitable for penaeid postlarval development, throughout most of the system. Compared to St Lucia, the Mfolozi-Msunduzi Estuary can be regarded as a poor alternative nursery area for penaeids during the summer peak postlarval recruitment period.

Benthic Macroinvertebrates as Ecological Indicators: Their Sensitivity to the Water Quality and Human Disturbances in a Tropical River

“…At the genus level, it was found that Macrobrachium from Palaemonidae was the most affected by salinity gradients and can be considered as the key indicator of water salinity. This corroborates the findings of other studies, which indicate that the life cycle or style of Macrobrachium is mainly related to estuary or water salinity (N'Zi et al, 2008;Collocott et al, 2014;Gangbe et al, 2016;Chen et al, 2018;Adam et al, 2019). Meanwhile, Mollusca taxon is associated with water eutrophication due to organic pollution.…”

“…From this study, crustaceans were found to be good indicators of the freshwater salinity. Indeed, crustaceans were dominated by two families (Palaemonidae and Atyidae) and well known to be influenced by EC or water salinity (Attrill et al, 1999;Cuesta et al, 2006;N'Zi et al, 2008;Collocott et al, 2014). At the genus level, it was found that Macrobrachium from Palaemonidae was the most affected by salinity gradients and can be considered as the key indicator of water salinity.…”

Assessment of water quality and its effect on prawn abundance in three tributaries of Shiwalik rivers: Chenab and Ravi of Jammu, India—a case study

“…3). A similar study conducted by Collocott et al (2014) and De Sousa et al (2020) showed summer months favor a high abundance of freshwater prawns and marine prawns, e.g., Farfantepenaeus brasiliensis, respectively.…”

Environmental Flow Requirements of Estuaries: Providing Resilience to Current and Future Climate and Direct Anthropogenic Changes

“…Seasonal changes in salinity driven by variations in freshwater discharge result in shifts in biological communities (Collocott et al, 2014), promoting species diversity by controlling dominant species, such as the mangrove Kandelia obovate in the Tanshui River estuary, Taiwan, allowing for succession (Shih et al, 2011). These fluctuations may also facilitate adaptation to highly varying salinity conditions, promoting species with wide distributions and competitive advantages (Sheaves, 1998).…”