Fish community structure as an indicator of the ecological significance: A study from Ulhas River Estuary, Western coast of India

Aim: The present study was aimed to analyze the ecological significance of Ulhas River estuary of the western coast of India using the taxonomic, functional and conservation aspects, and also to record an updated data base on the estuarine community structure. Methodology: Ichthyo faunal diversity was assessed by experimental fishing conducted at 3 selected stations using single day dolnets of code end mesh size of 10mm, from September 2017 to August 2018. The diversity of fish species was recorded considering the most relevant taxonomic classification data and further supplemented by the information pertaining to ecological roles played by the individual species (using guild approach) and the IUCN-conservation status. Results: There were 105 species, belonging to 4 classes, 19 orders, 44 families and 75 genera, recorded from Ulhas River Estuary. The class: Actinopterygii was the most diverse taxa, (including 12 orders, 32 families and 55 genera) among the total ichthyofauna reported. Order Perciformes was the most representative order of the class (40 species, 31 genera and 17 families), followed by Decapoda (21species, 8 genera and 6 families). Based on the estuarine usefunctional guild categorization, 51.42 % of the species were marine migrants, followed by amphidromous species (21.9%). Zoobenthivores (29.41%) was found to be the most dominant feeding guild followed by omnivores (19.6%). Based on the IUCN Red List, 53.33% of the fish species observed from Ulhas River Estuary were categorized as Not Evaluated, and 7% were Data Deficient, signifying the lack of information on biological aspects of the species along Indian waters. Tenualosa toli marked its presence under threatened category (Vulnerable) from Ulhas River Estuary. Interpretation: The abundance of marine migrants as well as the amphidromous species in the estuary signifies the use of this ecosystem for the nursery function of commercially important marine fisheries resources. Increased proportion of Not Evaluated and Data Deficient categories in the context of high level of anthropogenic stress demands for more updated documentation of the biodiversity and periodic changes in its ecological structure for formulating and implementing effective ecosystem-based management programs for such sensitive estuarine ecosystems.