His research has resulted in the discovery and description of twelve new species, three new genera and a unique new family of freshwater fish and shrimp from the rivers of the Western Ghats; contributed to the assessment of the extinction risk of over 100 species of South Asian freshwater fishes for the IUCN Red List, and helped generate the first information on the biology and population status of several endemic fish species of the Western Ghats. As of May 2019, Rajeev has published over 140 peer-reviewed papers (with >1300 citations) in some of the world's top journals in fisheries and conservation science including Fish and Fisheries, Biological Conservation, ; Marine Policy and Ambio.