Assessing the impact of climate change on inland fisheries in River Ganga and its plains in India

Abstract

Perceptible changes on a global and regional scale are evident in earth's climate. In India, observed changes include an increase of air temperature, regional monsoon variation, frequent droughts and a regional increase in severe storm incidence in coastal states of India, along with indication of Himalayan glacier recession. The impact is being felt in the inland aquatic resources and their fisheries. Analysis of time series data of 30 years from published literature and from current investigations on the River Ganga and water bodies in its plains, indicate increased minimum water temperatures; 1.5°C in colder stretches of the Ganga and 0.2 to 1.6°C in the aquaculture farms of the State of West Bengal in the Gangetic plains. Rainfall has also increased in the post monsoon months of September–December. The impact is manifested in the breeding failure of the Indian Major Carps (IMC) and a consequent decline in fish spawn availability in river Ganga. Whereas, in fish farm hatcheries on the plains, a positive impact on breeding was observed in the advancement and extension of the breeding period of IMC by 45–60 days. A geographic shift of warm water fish species Glossogobius gurius and Xenentodon cancila to the colder stretch of the river Ganga was recorded. The predator prey ratio in the middle stretch in the river Ganga has also declined from 1:4.2 to 1:1.4 in the last three decades. Fish production has shown a distinct change in the last two decades in the middle stretch of river Ganga where the contribution of IMC has decreased from 41.4% to 8.3% and that of miscellaneous and catfish species increased. Climate change in India will put an additional stress on ecological and socio-economic systems that are already facing pressure. Thus the specific climate variables of importance to inland fisheries viz. enhanced water temperature, extreme events like flood and drought, storms and water stress require specific adaptation actions. An integrated water shed management strategy is essential going from the village level to the river basin level in a unified manner. Finally, it is suggested that assessments of inland fisheries vulnerability to climate change should also assess economic scenarios since adaptive capacity is closely linked to the financial capabilities.