Assessment of tidal and lunar influence on larval diversity and distribution along the CVCAs of tropical Kali estuary, Karwar, West coast of India

Larval ingress, diversity and distributions were studied for a period of 13 months along the critically vulnerable areas of the tropical Kali estuary, Karwar, West coast of India. Planktonic and hydrological samplings were carried out following the tidal regime and lunar periodicity at Zone (1) (categorized as euhaline <30 PSU to polyhaline 18.0 to 30 PSU in condition), subsequently, Zone (2) (mesohaline 5.0 to 18.0 PSU to oligohaline 0.5 to 5.0 PSU). A total of 26 different larval forms were recorded, representing 10 taxa, of which crustaceans are dominant. The predominant larval forms documented during the study period were Copepod nauplii, Barnacle nauplii, Eggs & fish larvae and Crab zoea, respectively. Larval forms, viz., Planula, Cercaria, Rhabditiform, Alima (Squilla), Bipinnaria, Ophiopluteus and Doliolaria distributions was restricted to euhaline zone due to tidal ingress. The distribution of Bivalve, Crab and Shrimp larvae along the mesohaline zone represents larval recruitment in their preferred habitat. The larval distribution showed typical seasonal variation governed by hydrological parameters and tidal regimes. Multivariate RDA analysis of larval distributions attributed to salinity and water temperature. The Shannon-Wiener diversity index was higher (2.92) during the post-monsoon season in particular to full moon of the flood tide. Overall, the Kali Estuary represents a suitable habitat for juvenile nurture and larval ingress enhances the estuarine productivity.