Invasion and impacts of alien fish species in the Ganga River, India

Abstract

In this study, we document an increasing trend of catches of alien fish species from the Ganga River system. The changing fishery during 1980 to 2011 and the fish yield rate (kg km −1 ) are positively correlated with an invasion coefficient index (I xi ) of alien species within the river. The reproductive propagule pressure (PPP) of alien fishes (Cyprinus carpio, Oreochromis niloticus, Aristichthys nobilis, Ctenopharyngodon idella, Hypophthalmichthys molitrix and Clarias gariepinus) was determined and found to be 19.45×10 6 for C. carpio, 0.33×10 6 for O. niloticus and 0.82×10 6 for A. nobilis at confluences suggesting that these alien species may be migrating into new habitats. Further, these invaded species exhibited all reproductive stages, indicating their likely establishment within the river. The trophic spectrum of alien fishes spanned all levels and the gut repetitive index (GRI) indicated that that food items in most of the fishes were similar showing early trends of food-web alteration and biotic homogenization. The results of this study suggested a continuous decline in the catch of local fishes by wet weight, particularly Indian major carps (IMC) from 128.91 kg km −1 to 38.58 kg km −1 owing to increased catches of alien species from nil to 384.27 kg km −1 . Invasion of alien species in the Ganga River represented one of many possible causes of the decline in river health and overall loss of native aquatic communities.

Successful reproduction of common carp Cyprinus carpio in irrigation waterways

“…), C. carpio is either historically recognised as a pest species (USA: Panek ) or being monitored as potentially invasive (India: Singh et al . , ). By contrast, in some European countries (e.g.…”

Occurrence of Ornamental Fishes:A Looming Danger for Inland Fish Diversity of India

“…For instance, studies from the Yamuna and Ganga rivers have shown that there is a constant increase in the yield of alien varieties. In Yamuna, the occurrence of tilapia, African catfish, silver carp and Gambusia is higher and the yield is spiralling every year 10,15 . Singh et al 15 reported the highest yield of exotic variety of 384.27 kg/km in the Ganga.…”

“…In Yamuna, the occurrence of tilapia, African catfish, silver carp and Gambusia is higher and the yield is spiralling every year 10,15 . Singh et al 15 reported the highest yield of exotic variety of 384.27 kg/km in the Ganga. Likewise, studies from Kerala have shown the high occurrence of tilapia species in inland waters (up to 25%), due to which native species such as Puntius dubius and Labeo kontius face local extinction 13 .…”

“…Likewise, studies from Kerala have shown the high occurrence of tilapia species in inland waters (up to 25%), due to which native species such as Puntius dubius and Labeo kontius face local extinction 13 . Also, overpopulation of ornamental sucker mouth catfish Pterygoplichthys multiradiatus and Pterygoplichthys pardalis has resulted in the decline of commercially important inland native fish in Kerala and Tamil Nadu, respectively 15,16 . In India, 31 aquaculture species, 600 ornamental varieties and 2 species of larvicidal fish have been identified as exotic 17,18 .…”

“…Recent studies in several parts of India have highlighted the fact that freshwater fish biodiversity is depleting at an alarming rate due to invasion of commercially important and ornamental, exotic fish species 3,6,7,10,14 . Many native species, especially Indian major carps in various riverine systems have been critically depleted due to the introduction of commercially important exotic species such as Nile/red tilapia (Oreochromis niloticus), African catfish (Clarias gariepinus), Thai pangus (Pangasiandon hypophthalmus) and common carp (Cyprinus carpio) 3,10,15 . For instance, studies from the Yamuna and Ganga rivers have shown that there is a constant increase in the yield of alien varieties.…”