Impacts and vulnerability of inland fisheries to climate change in the Ganga River system in India

Abstract

Climate change is evident in India as manifested by increased air temperatures, regional variation in the monsoon, frequent occurrence of droughts, and a regional increase in severe storm incidence in coastal states of India. The impacts are evident for freshwater fisheries and fishers of the River Ganga and the water bodies in its plains and deltaic areas. Analysis of time series data for 32 years from published literature and from current investigations showed a 0.99°C increase in the minimum water temperature recorded in the upper stretch of River Ganga and 0.5 to 1.4°C increases in aquaculture water on the Gangetic Plains of West Bengal. The minimum air temperature showed a 15% shift upwards during the colder months of January–February. Rainfall showed a 1% increase in the post monsoon months of September–December. The impacts were manifest in a geographic shift of warm water fish species such as Glossogobius giuris, Xenentodon cancila into the colder stretch of the River Ganga. The breeding of the Indian Major Carps (IMC) has been affected and a consequent decline in fish spawn availability in River Ganga recorded. However a positive impact on breeding in fish farm hatcheries in the Gangetic Plains was evident in the advancement and extension of the breeding period for IMC by 45–60 days. Drought in West Bengal during 2009 was evident in rainfall deficits of 29% and 27% in the districts of North 24 Parganas and Bankura, respectively, in the fish breeding months of March–September and 92% of fish spawn hatcheries were affected. These districts recorded losses on average 61% to 73% of fish spawn during 2009 compared to the previous four years. A study of the potential impact of cyclones and storms on saline water inundation using a digital elevation model generated for coastal district of South 24 Parganas indicated the potential for 3% to 11% submergence of aquaculture areas in response to 1 to 2 meter rises due to sea water incursions. The inland fisheries sector in coming years will face stiff competition for water from the industrial, municipal and agricultural sectors and climate change will compound these problems. Under such a scenario implementation of integrated water resource management involving different stake holders of fresh water would be the most effective management approach.