Ecological assessment of the Amazon sailfin catfish (Pterygoplichthys species) within the Indian freshwaters: a mesocosm-based approach

Amazon sailfin catfish is relatively a recent invader to the open waters of India, and studies on ecological assessment of the species within the Indian freshwaters are lacking. In the present study, to assess the ecological impact of catfish, we established mesocosms mimicking the Indian freshwaters within natural ponds of eastern India using three species of native fish, rohu, catla and mrigal, and for two size classes, small (10-20 cm length) and large (20-30 cm length) native fishes. Mesocosms were maintained with (test) and without the catfish (control), and length and weight of native fish, zooplankton abundance, and several hydrological and soil parameters were measured at a monthly interval for a period of 120-days. The catfish had a significant (P<0.05) negative impact on growth of small-size rohu only. However, we found no significant (P>0.05) differences in abiotic parameters and zooplankton abundance between control and test ponds for the small-size class. We speculate that reduced growth of rohu could be due to competition from catfish in the context of feeding, and not due to modification of abiotic environment. Thus, we emphasize upon the need for behavioral studies to further assess the impact of the catfish.