Global warming and its associated climatic change is the major environmental challenge of the 21st century. It has become a threat to the livelihood and economies of countries dependent on natural ecosystems of the planet including those in the fisheries and aquaculture sector. While the importance of fisheries and aquaculture is often less understood, the implications of climate change for this sector in India are difficult to ignore. The sector provides direct and indirect engagement to 14 million people and any potential direct or indirect effect of climate change will have an immense implication on the food security of the nation. The climate change predictions for India of relevance to fisheries as consolidated by India’s Initial National Communication (NATCOM), 2004 are:
Surface Temperature: At the national level, increase of 0.4°C has been observed in surface air temperatures over the past century.
Rainfall: The observed monsoon rainfall at the all-India level does not show any significant trend but regional monsoon variations have been recorded.
Extreme Weather Events: Trends are observed in multi-decadal periods of more frequent, followed by less severe droughts. There has been an overall increasing trend in severe storm incidence along the coast at the rate of 0.011 event per year.
Impacts on Himalayan Glaciers: The available monitoring data on Himalayan glaciers indicates that while recession of some glaciers have occurred in some Himalayan regions in recent years, the trend is not consistent across the entire mountain chain.
Sea level rise: Inter-governmental Panel on Climate Change has projected that the global annual seawater temperature and sea level would rise by 0.8 to 2.5oC and 8 to 25 cm, respectively, by 2050 (IPCC, 2007).
Impact on Freshwater ecosystems
The impact of climate alteration will be perceptible in the major river systems of India especially the Himalayan glacier-supported, perennial rivers such as Indus, Ganga and Brahmaputra. About 75 per cent of the discharge in Himalayan rivers occur during May-September. Similarly other non-perennial rivers arising in the Deccan plateau like the Narmada, Mahi, Tapi, Godavari and Mahanadi shall face either acute or regular water shortage; or excessive flood conditions as in the Mahanadi (NATCOM, 2004). River flow is an important factor determining the physical structure of a river. The hydrological processes in the watershed and the rate of downstream discharge determine the depth, duration and frequency of inundation of the floodplain, which periodically becomes a part of the riverine habitat. Thus the riverine flow characteristics determine the diversity of habitats and biotic communities of both the river and its floodplains and directly affect the life cycle of fishes.
Ganga river basin
Fish breeding: Analysis of the seasonal pattern of rainfall in the middle stretch of river Ganga based on the monthly data of rainfall at Allahabad from 1979-2009 split into three equal periods—Jan-April, May-August and September-December reveal that the percentage of total rainfall in the peak fish breeding period (May-August) declined by 7 per cent whereas it increased by 4 per cent in the post-breeding period (September-December). This shift and decrease in the rainfall pattern has deprived the river of the adequate flood level required for inundating the Gangetic floodplains where majority of the carps breed during the monsoon months (June-September). The failure in breeding has affected the recruitment of the young ones especially of the Indian major carps in the river. (K Vass, et al., 2009, ‘Assessing the impact of climate change on inland fisheries in River Ganges and its plains in India’, Aquatic Ecosystem Health and Management; T Bhattacharyya et al., (eds), 2013, Climate change and Agriculture, Stadium Press)
Geographic shift: The annual mean minimum water temperature in the upper colder stretch of river Ganga at Haridwar increased by 0.99ºC during the period 1980-2009. Warming of the upper stretch initiated a geographic shift of the warm water fish G. giuris P. ticto, X. cancila, M. vittatus from the middle stretch of the river to the upper stretch at Haridwar. (ibid.)
Positive impact on aquaculture: Analysis of the pattern of the air temperature data during 1980-2009 for the breeding month (April-August) of the Indian carps from four fish producing districts of West Bengal, indicates that the mean minimum air temperature increased by 0.67-0.1ºC along with a shift towards higher temperature during the colder months of January-February. The seasonal pattern of rainfall over the years 1980-2009 decreased by 5 per cent in the monsoon months (May-August) and increased by 4 per cent in the post monsoon months (September-December). Similar trend of seasonal variation in temperature and rainfall has been observed in the fish producing districts of Odisha. These climatic changes had a beneficial effect on the spawning of Indian major carps in the fish hatcheries of West Bengal, Odisha and Assam where the breeding period has advanced to March with an extension of the breeding season of carps from 110-120 to 160-170 days at present (Fig 1). Thus fish farmers are getting an extended duration of 45-60 days to breed the fish (ibid.)
Influence of climatic factors on fish
The time series data (1994-2009) of seven ecological variables related to climate influencing the fish habitat of 14 major rivers of India were quantitatively analysed by the author for determining their influence on the richness of fish species. It was revealed that the surface area of the river basin; followed by fish habitat availability potential; and, a synthesis of the variables of rainfall, discharge and sediment load were the most influential determinants of species richness. These three variables related to hydrology and morphology significantly influence the riverine habitat structure for fish and their alteration can lead to changes in fish species richness in the river. We call this compounded effect of the three variables as ‘fish habitat availability’ potential of river. The predicted loss of fish species is evident at a 10 per cent alteration in the ecological variables of the rivers in majority of the rivers and can be useful for river planners and conservationists.
It was also seen that during the drought of 2009 the two highest fish seed producing district of West Bengal—Bankura and 24 Parganas recorded 27-29 per cent deficient rainfall during the fish breeding months (March-September) in comparison to the time period 1999-2008. During this period 92 per cent of the fish seed hatcheries were affected and the fish seed production in the district North 24 Parganas dropped to 4368 million spawn during 2009 compared to 4532 million during 2008 (Hand Book on Fishery Statistics 2009, West Bengal). Economic analysis indicate a loss of 61 to 73 per cent fish seed in the districts during 2009-10 compared to the last four years average.
Vulnerability of Inland Fisheries
The extent to which people and systems are affected by climate change (their vulnerability) is determined by three factors; their exposure to specific change, their sensitivity to that change and their ability to respond to impacts or take advantage of opportunities (IPCC, 2007). Based on the functional relationship of the components sensitivity, exposure and adaptive capacity using 19 indicators related to inland fisheries a composite vulnerability index (Fig 2) was developed for 13 fish producing districts of West Bengal. The assessment revealed inland fisheries in 5 districts of West Bengal to be highly vulnerable to climate change with the composite vulnerability index (VI) ranging from 0.61 to 0.53. In these districts inland fisheries was sensitive (VI range 0.14-0.20) to exposure of high variation in rainfall, air temperature and cyclones (VI range 0.07-0.21), with low adaptive capacity (VI range 0.17-0.26). The vulnerability profiles developed provide a frame work for assessing vulnerability of the fisheries sector to climate change in India. (CIFRI/NPCC Annual Report, (2008-2009), ‘Impact, Adaptation and Vulnerability of Indian Agriculture to Climate Change’, Indian Council of Agricultural Research Network Project, Government of India).
Developing a resilience
It is apparent from the above discussion that climate change can impact the aquatic ecosystems and fisheries already subjected to various anthropogenic stresses. Thus appropriate adaptation strategies are needed for the inland fisheries sector to cope up with the impending threats. Without effective planning, aquatic ecosystems, fisheries and aquaculture can potentially be affected by the adaptation measures undertaken by other sectors. For example, while adapting to an increased demand for water for irrigation, the supply side option would aim at increasing supply, which has potential environmental impacts. On the other hand demand side options aim at reducing demand by increasing irrigation efficiency through improved technology and changes in cropping pattern by switching to crops that require less or no irrigation. The demand side options in most cases are environment friendly and would appear to be better choices for those interested in fish and fisheries. It is obvious that the future of fisheries will be shaped by cross-sectoral solutions to the current problems. Enhancing investment in fisheries and aquatic ecosystems is an investment in the ‘liquid assets’ of adaptation because this sector would buffer the society from climate related risks.