Invasive Amazon sailfin catfish (<i>Pterygoplichthys pardalis</i>) impacts the survivability and growth of native food fishes in India

The prevalence of sailfin catfishes ( Pterygoplichthys spp.) in inland waters, including vast aquaculture systems of India is rising. This might be a serious threat to the country’s native freshwater biological resources and aquaculture production. Therefore, studies were carried out to evaluate the impact of Amazon sailfin catfish Pterygoplichthys pardalis on different life-stages of native fishes. First, we analyzed the impact of three different size classes (small: 9.95 ± 0.70 cm, medium: 21.74 ± 0.87 cm and large: 30.81 ± 1.59 cm total length) of Amazon sailfin catfish on the survival of early life-stages (eggs, hatchlings, first-feeding fry, and 10-day-old fry) of two native fishes; native carp Labeo rohita (rohu) and native catfish Ompok bimaculatus (butter catfish). All size classes of Amazon sailfin catfish showed preference towards fish eggs over aquatic macro-invertebrates ( Tubifex worms) and ingested over 90% of the eggs of both the native species. However, their effects on native species’ mobile life stages (hatchlings forth) were found to be insignificant in terms of mortality. We then assessed the competition between advanced stages (fingerlings, advanced fingerlings, and sub-adult) of the Amazon sailfin catfish and the native fishes by evaluating growth and survival in three different experimental setups (indoor tanks with artificial feeds; outdoor tanks with natural food and artificial feed; and earthen pond with natural food) and in different combinations for a period of three to six months. In indoor experiment, no discernible impact of Amazon sailfin catfish on the growth of fingerlings of native species was found. But, in the outdoor experiment, growth of advanced fingerlings of rohu and butter catfish was decreased by 18.8–23.4% and 28.9–36.7%, respectively, in low- and high-biomass Amazon sailfin catfish treatments. The growth of rohu and butter catfish sub-adult was also reduced in the pond experiment, by 29.7% and 32.2%, respectively. However, impact of Amazon sailfin catfish on survival of native fish species at advanced stages was found minimal. Overall findings of this study indicate that sailfin catfish may have an adverse effect on the survival and growth of native fishes by either directly consuming or destroying native fish eggs or by competing with them for food and space.