Fish community structure and functional guild composition in an anthropogenically impacted, temporarily closed sandbar estuary.

This study investigates the fish assemblage in a temporarily-closed sandbar estuary along India's west coast, across different zones and seasons. Moderate species diversity (54 species), low species abundance, varying fish diversity from lower to upper estuarine gradient (higher counts in lower zones, and decreasing from middle to upper zones), and higher prevalence of marine migrants (estuarine use) and piscivorous species (feeding mode) were the significant characteristics of the estuary. Distinct spatial, seasonal, and estuarine mouth state-based variations were recorded in the estuary, based on diversity indices and count of taxa. Peak diversity and abundance were noted during the pre-monsoon, and during the open mouth state of the estuary. The entire estuarine gradient is anthropogenically impacted by a multitude of stressors, except at the estuarine mouth region, which is favored by marine connectivity. The fish assemblage structure in Poonthura estuary (PE) has thus far remained unaffected by anthropogenic disturbances. Nevertheless, growth and nursery function of the estuary have been significantly compromised. The predominance of juvenile fish in the ecosystem, and prevailing anthropogenic stressors from point and non-point sources underscore the necessity for long-term maintenance of the population of coastal species, as well as a need for developing and implementing urgent management strategies for this fragile ecosystem.

Characterization of fish community structure and an estuarine fish community index for temporarily closed estuaries (TCEs) from India's south-western coast.

We present for the first time, data on fish assemblage structure for ten temporarily closed estuaries (TCEs) along the south-western coast of India. Fish community structure differed significantly between TCEs based on species presence/absence, estuarine use and feeding mode. Marine migrant and freshwater stragglers dominated the 'fish guilds', while piscivores and zoobenthivores were the major feeding guilds, in all estuaries. We used the Estuarine Fish Community Index (EFCI) and a Combined Anthropogenic Pressure Index (CPI) to determine the ecological quality of TCEs. The application of functional guilds and EFCI successfully represented the use of TCEs by fish communities, and also the functional similarities existing between fish assemblages of these estuaries, despite considerable taxonomic, physical and chemical differences. EFCI indicated that the ecological health of TCEs in south-western India ranges from 'poor' to 'good'. We also established a significant relationship between CPI, EFCI and ecological quality in various TCEs using the Generalized Linear Model (GLM).