Prelude: Research and management of aquatic nonindigenous species in India

Abstract

The introduction of nonindigenous species to freshwater (inland) and coastal marine habitats is a global phenomenon, with many aquatic habitats subject to severe, irreversible negative impacts resulting from competition for space and resources between indigenous and nonindigenous species, as well their parasites and pathogens (Gallardo et al., 2016). Despite the accumulating ecological and economic impacts in aquatic habitats, research and management efforts in aquatic systems are much lower than for terrestrial habitats, and are unevenly distributed geographically, taxonomically and by introduction pathway (Bailey et al., 2020; Seebens et al., 2017). These global trends are mirrored within India, although effort has been comparatively low. A basic search using keywords “nonindigenous/nonnative/introduced/alien aquatic/marine species” and “India” reveals only 36 papers in the scientific literature on aquatic nonindigenous species in India (Web of Science, accessed 29 June 2021). The majority of these publications are comprised of surveys/new records of nonindigenous species (16 studies) or assess risk and management options (10 studies) while a few investigate invasion dynamics (5 studies) and impacts (5 studies) (Table 1). Subba Rao (2005) identifies 205 nonindigenous taxa reported as new records in the Indian Seas between 1960-2004, despite limited scientific attention to the subject in these waters. A majority of these taxa, comprised of fishes, polychaete worms, algae, crustaceans, molluscs, ciliates, fungi, ascidians and other taxa, are likely associated with ships’ ballast water and/or biofouling as the transport pathways (Subba Rao, 2005). Aquatic nonindigenous species are frequently underreported due to limited search effort and insufficient taxonomic expertise (especially for smaller/microscopic taxa)(Carlton and Fowler, 2018; Ojaveer et al., 2017). Like other parts of the world, fishes are one of the best-studied aquatic taxa, with more than 2300 species reported, including at least 300 nonindigenous species, from India’s rivers, lakes and reservoirs – typically as (unauthorized) releases or escapees associated with aquaria and aquaculture activities (Singh and Lakra, 2011). (Note that Singh, this issue, provides an updated number of 532 nonindigenous fishes in India). The inventory of nonindigenous species in India is certainly incomplete, as, like all other regions globally, records are compromised by incomplete historical records impacting the ability to determine the true origin of many species as indigenous or nonindigenous (Carlton, 1996) and an absence of regular and targeted monitoring (such as Hayes et al. 2019; see also Ojaveer et al. 2014). While there has been some consideration of transportation pathways associated with introductions to India, there are often a number of mechanisms possible for each species, and dedicated research will be needed to identify responsible pathways and develop effective management strategies. In addition to ships’ ballast water and biofouling, aquaculture and aquarium pathways, recent literature points to bait sales, live prayer release, internet commerce and anthropogenic marine litter as potentially