Non-native freshwater fishes in India: existing evidence and knowledge gaps

Abstract

India has experienced the introduction of numerous non-native fish species (NNF), some of which have caused ecological and economic impacts. This systematic review provides a currently lacking overview of NNF research in India, potential biases, available evidence, and knowledge gaps. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework, we identified a total of 332 records, documenting the presence of 58 NNF distributed across 17 basins, and 19 translocated species in India. The Ganga was the most studied basin (113 studies), followed by the West Flowing Rivers Tadri to Kanyakumari basin (37 studies), however, with 30 NNF reported from each of these basins. We demonstrate how these results can be due to saturated sampling in the Ganga and identify which basins might be currently understudied. We also illustrate how extreme floods precipitated an increase in NNF into rivers and lakes from confinement in the West Flowing Rivers Tadri to Kanyakumari basin. The common carp, Cyprinus carpio, was the most frequently reported NNF (160 times), while Mozambique tilapia, Oreochromis mossambicus, was the most widely distributed NNF (13 basins). We found there is a growing number of publications in the field, but that up to 40% of studies have appeared in potentially predatory journals. A minority of studies (44%) investigated NNF impacts, most of which used data from the literature (58%) and reported only qualitative impacts (69%). Most documented impacts were ecological (79%), while some were socio-economic (11%) or both (10%). Only 18% of the studies addressed NNF management. The knowledge synthesized and the gaps identified in this study might serve as a basis for future studies and be useful for efficiently allocating limited resources for investigating NNF in India.