Assessing and predicting fishing impacts and temporal shifts in the fisheries of a Tropical Reservoir in India
Authors: KHAN M FEROZ , Panikkar Preetha , Ramya Vijayakumar Leela , Mol Salim Sibina , Das Basanta Kumar , Sarkar Uttam Kumar , Vijayakumar Muttanahalli Eregowda 
Published: March 2022

Abstract
Food Web Modelling is used as a method for an interpretation of ecological processes and for studying the impact of fishing on biodiversity. An overview of ecological dynamics, as well as the significance of interactions between functional groups was obtained by modelling Ecopath with Ecosim in Karapuzha reservoir, in India. The modelling exercise revealed fishing and predator pre-interaction from the main drivers of this ecosystem. This is the first time in the Indian reservoir system, Ecopath with Ecosim was used to predict temporal shifts caused by fishing impacts. The mean trophic level of the catch was 2.53, not varying much throughout the entire time series and the Kempton Index (Biomass diversity) has declined slightly. The values of the L index were between the reference values of the L index 25% and L index 50%, implying overfishing, the favourable impact of gillnet fishing on some indegenous fish was likely due to the predation release of invasive species such as C. gariepinus since this fish was caught by gillnets. Such results suggest more work to determine if gillnet fishing in this reservoir will help mitigate the negative effects of invasive fish. Snakeheads, however, which have high market demand, appear not to be investigating the ability of gillnet fishing in this reservoir to contribute to mitigating the negative effects of invasive species. The modelling of Karapuzha reservoir showed a decline in the predicted biomass of some groups (Eels, Snakeheads, Minor Carps and Barbs) because of trophic response and relationships, and failed to give maximum sustainable yield .The new tools are designed to support policy decisions and incorporated into frameworks to integrate the effects of the stressors mentioned above to promote policy decision-making, particularly for ecosystem-based management (EBM), which tests the environment. The Ecosim routine shows that the presence of major carps does not affect other functional environmental organisations in this state and has predicted those groups and are not detrimental. This study will assist Indian Major Carp Stock Managers in enhancing fish productivity. New tools like this support policy-making integration with the impact of aforementioned stressors in reservoirs. This is the first time the Ecopath with Ecosim reservoir system has been predicted to temporarily shift due to fishing effects. This is the first time. This study helps manage resource conservation and management of informed and ecosystem-based fisheries choices. Our study analysed the social and economic elements of Karapuzha Fisheries which might link all these subsystems within a socio-ecological scenario. The modelling of the Karapuzha Reservoir provided an overall understanding of eco-dynamics and the role of interactions among the fish groups particularly since it eliminates the detrimental effects, in particular it eliminates the detrimental effects imposed by the invasive fish (C. gariepinus O.mossambicus). Gillnet fishing has a positive impact on several indigenous fish.