Data Sheet 1_Spatial heterogeneity of epipelagic ichthyoplankton and its link to environmental drivers in the eastern Arabian sea during the early summer monsoon.docx

Assessing the spatial distribution of ichthyoplankton populations is crucial for understanding marine ecosystems. However, identifying the factors that influence their abundance and distribution presents a significant challenge, where seasonal change plays an essential role in the environmental variables. In this study, we analyzed abiotic and biotic factors from the eastern Arabian Sea during the early summer monsoon to characterize ichthyoplankton assemblages and examine the impact of physical processes and environmental variables on their spatial abundance and distribution. Although the eastern Arabian Sea (EAS) is one of the most productive fishing areas in the Indian Ocean, information on ichthyoplankton in this region has been limited. Our findings reveal a heterogeneous distribution of ichtyoplankton across the EAS, which was significantly influenced by the upwelling-driven productive environment characterizing the EAS. Statistical analyses, including Generalized Additive Models (GAMs) and Principal Component Analysis (PCA), indicated a strong positive correlation between nutrient levels, chlorophyll-a concentrations, and zooplankton biomass with the abundance of fish eggs and larvae. Conversely, sea surface temperature and salinity were found to have negative relationship with ichthyoplankton abundance and distribution. These findings provide valuable insights into the ecology of ichthyoplankton within a major eastern boundary upwelling ecosystem highlighting the impact of physical processes and varying environmental drivers on ichthyoplankton populations in a productive marine environment.