Invasion meltdown and burgeoning threats of invasive fish species in inland waters of India in the era of climate change

Abstract

Cyprinus carpio, Oreochromis niloticus and Clarias gariepinus are the most abundantly captured invasive fish species in the mid-stretch of the Ganga river. Fish yield and biomass data based on mean abundance by weight was calculated using algorithms and spatio-temporal population dynamics model for future prediction of these invasive fish species. Temporal biomass forecast based on mean abundance by wieght for the period from 2020 to 2029 was determined. The findings of this study predicted fish yield of 176 ±16.33 kg km-1 day-1 C. carpio and 55.43 ± 6.4 kg km-1 day-1 O. niloticus during 2029 which might result into 117.87% and 116.9% rise in temporal biomass of Common Carp and Tilapia respectively in a decade's time while 139.2% rise in temporal biomass was predicted for the invasive African catfish. The yield of invasive Common Carp, Tilapia and African Catfish was correlated with rainfall and temperature data using ANOVA and we found that variance was F=1.36; p=0.263 for C. carpio; F=1.60; p=0.326 for O. niloticus and F=1.63; p=0.101 for C. gariepinus, indicating that variance was very close for Tilapia and African Catfish. The observed values of variance indicated that climatic changes had more impact to these two species than to the Common Carp. The concrete and forecast values were calculated considering 95% lower and upper level of confidence, which was significant (p<0.05) and the annual regression was found to be p<0.464, p<0.419 and p<0.499 for C. carpio, O. niloticus and C. gariepinus, respectively. Further, interactive performance of invaded C. carpio, O. niloticus and C. gariepinus was also assessed for understanding invasion meltdown. The results of mean abundance by weight based yield forecast of invaded Tilapia, Common Carp and African Catfish for the period of 2020 to 2029 suggest a stable production in the Ganga River in years to come. It also manifests a positive pattern of invasion in the times of climate change displaying invasion meltdown. This suggests increased pressures of fish invasions on temporal and spatial scales, and imposing new management challenges for freshwater ecosystems.