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.

Introduction

The climate of the earth in the past few decades has shown perceptible changes both on global and regional scales manifested by increase in atmospheric and water temperatures. The Inter –Governmental Panel on Climate Change (IPCC), in its recently released report has reconfirmed that the global atmospheric concentrations of carbon dioxide, methane and nitrous oxide, greenhouse gases (GHGs), have increased markedly as a result of human activities since 1950, and now far exceed pre-industrial values determined from ice cores spanning many thousands of years (IPCC, 2007). Some of the observed changes of climate in India as reported by Indian National Communication 2004 (NATCOM) to United Nations Framework Convention on Climate Change (UNFCCC) indicate an increase of 0.4°C in surface air temperature over the past century. Regional monsoon variations recorded though the monsoon rainfalls at the all India level do not show any significant trend. There is a trend of more frequent multi-decadal drought followed by fewer droughts and an overall increase in severe storm incidence especially in the states of Gujarat and West Bengal in India. There are indications of recession of some of the Himalayan glaciers which are the source of water for the perennial rivers such as Ganga, Indus and Brahmaputra, but the trend is not consistent across the entire mountain chain. In a developing country like India, climate change could represent an additional stress on ecological and socioeconomic systems that are already facing tremendous pressures due to rapid urbanization and economic development. With its huge and growing population, a low-lying coastline, and an economy that is closely tied to its natural resource base, India is considered vulnerable to the impacts of climate change. There are 12 major rivers in India with a cumulative catchment area of 252.8 M ha. Of the major rivers, the Ganga-Brahmaputra Meghna system is the largest with a catchment of about 110 M ha; ie. 43% of the cumulative catchment area of all the major river basins. Further, about 40% of the surface water resources are utilized presently in this system. These river systems in India harbour one of the richest fish biodiversity resources in the world. The Gangetic river system alone harbours around 265 species of fish and supports a complex mix of artisanal, subsistence, traditional and semi-intensive culture fisheries based on the main river and adjoining water bodies of the gangetic plains situated mainly in the three Indian states of Uttar Pradesh, Bihar and West Bengal. With this background, time series data on some of the climate variables and its impact on the fishery of river Ganga and on aquaculture in the earthen static water bodies in its plains were analysed.

Impact on hydrology and Inland water resources

As global warming continues to increase the atmosphere temperature, it will lead to a continuous shift of the zero temperature line (snow line) toward higher altitudes. Thus glaciers will receive more liquid precipitation and less monsoonal solid precipitation. The shift in snowline will result in lesser input to glacier mass balance during summer periods. Therefore, higher atmospheric temperature and more liquid precipitation at higher altitude in the Himalayas will lead to rapid retreat of glaciers and downstream flooding in the coming future (Hasnain, 2002; Kadota et al., 1993). Its impact will be felt in the rivers and associated ecosystems. This alteration in the hydrologic pattern of the rivers and associated wetlands will definitely impact inland fisheries.

Rivers

Some of the changes in the hydrologic system (Arnell et al., 2001) that are relevant to fish and fisheries are: flood magnitude and frequency could increase owing to more intense precipitation events; water temperature will increase; low flows would be more severe owing to increased evaporation; peak stream flow would move from spring to winter owing to earlier thaw. This is evident in the USA where an increase in the proportion of annual precipitation associated with extremes has been occurring since the early 1900s and future scenarios (Kunkel and Andsager, 2001) suggest that this will continue into the future. It is apparent that global warming will affect the flow regime of rivers and will have a profound effect on the life history of fishes as is evident in temperate fishes (Meisner and Shuter, 1992).

The major river systems of India which will be impacted in a climate alteration scenario are the Himalayan glacier-supported, mighty, perennial rivers such as Indus, Ganga and Brahmaputra, which are the lifelines of millions of people. About 75 percent of discharges in Himalayan rivers occur during May–September due to rising atmospheric temperature and precipitation. Similarly other major rivers which are not snow fed arising in the mid Deccan plateau of India like the Narmada, Mahi, Tapi, Godavari and Mahanadi will have either acute or regular water shortages or face excessive flood conditions as in Mahanadi (Ministry of Environment and Forest, 2004).

Climate Change and Water Availability

Projections of water balance components for the 12 river basins (Ministry of Environment and Forest, 2004) compare water balance components expressed as percentage of rainfall for both control and climate change scenarios (Table 1). The control is based on the daily weather generated by HaD RM2 control climate scenarios (1981–2000). The model was run using climate scenarios projected for the period 2041–2060. It is observed that the impacts are different in different catchments. The increase in rainfall due to climate change does not result in an increase in the surface run-off as may be generally expected. For example, in the case of the Cauvery river basin, an increase of 2.7% has been projected in the rainfall, but the run-off is projected to reduce by about 2% and the evapotranspiration to increase by about 2%. This may be either due to increase in temperature and/or change in rainfall distribution in time. Similarly, a reduction in rainfall in the Narmada is likely to result in an increase in the run-off and a reduction in the evapotranspiration that is again contrary to the usual myth. It may be observed that even though an increase in precipitation is projected for the Mahanadi, Brahmani, Ganga, Godavari, and Cauvery basins for the Climate Change Scenario, the corresponding total run-off for all these basins has not necessarily increased. The Sabarmati and Luni basins are likely to experience a decrease in precipitation and consequent decrease of total run-off to the tune of two-thirds of the prevailing run-off. This may lead to severe drought conditions as generated using a future climate change scenario.

Rivers differ a great deal in the amount of water they carry depending upon the precipitation in their catchments and other sources of water (e.g. snowmelt), as well as factors that determine runoff, infiltration and evaporation. Flow is an important factor determining the physical structure of a river and thus maintaining in-stream habitats. The range and variability of flows are just as important as the volume of water within a system. Flows also differ in their seasonal flow patterns, size and frequency, duration and the rate of rise and fall of a flow event. Changes in any of the flow characteristics are marked by a reduction in habitat complexity and the diversity of plants and animals. River flows interact with ground waters which may be recharged or contribute to the river flow (discharge) at different times of the year.

Further, flow variability directly affects many life cycle stages of fish; for example, flooding or its receding serves as a cue for migration and spawning.

Wetlands

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 river. The area of floodplain immediately adjacent to, and influenced by the river is often distinguished as the riparian zone. The riparian zone and the floodplain are important riverine habitats; they form a critical link between terrestrial and aquatic ecosystems. River flows determine the nature and strength of a river's interaction with its floodplain, and consequently the diversity of habitats and biotic communities. Any human activity that directly or indirectly impinges upon the flows has an impact on fishery resources.

Air temperature and rainfall pattern changes in the Gangetic areas

Seasonal pattern of rainfall in the middle stretch of river Ganga

Analysis of the monthly data of rainfall at Allahabad site of the middle stretch of river Ganga from 1974-2003 split into three equal periods P1 (Jan–April) P2, (May–Aug) and P3 (Sep.-Dec) revealed that the percentage of total rainfall in the peak breeding period (May–Aug.) declined by 5% whereas it increased by 7% in the post-breeding period when resorption of eggs of Indian Major Carps begins (Figure 1).

Water temperature changes in the upper stretch of river Ganga

In the upper stretch of river Ganga at Haridwar during the period 1970–86 the annual mean minimum water temperature was 12.9°C (13°C), while during the period 1987–2003 it increased to 14.5°C, an increase of 1.5°C is thus evident (Figure 2). As a result the stretch of river Ganga around Haridwar has become a more congenial habitat for warm water fishes.

Trend of air and water temperature changes in the Gangetic plains (West Bengal)

Temperature alteration

A semi tropical country like India shows a tendency of increase in temperature with the end of the winter months January–February through spring and finally to summer from the months of April–May. During this period the increase in temperature is not linear as there are sudden temperature increases within a short period of time. The months January to April are the transition months from winter to summer. Analysis of the air temperature data (IMD, 1986–2005) during the breeding months of Indian fishes carps (April–August) from four districts in the gangetic plains of India where aquaculture hatchery farms are located indicate that the mean maximum air temperature has increased by 0.37°C in the 24 Parganas (N) district and by 0.09°C in Burdwan while the mean minimum air temperature increased by 0.67°C in the 24 Parganas (N) district, by 1.57°C in district Bankura while the mean minimum air temperature increased by 0.18°C in Burdwan district.

Simultaneously, the differences of temperature between the months Jan–Feb, Feb-Mar and Mar–April during the period 1961–05 indicated a shift towards higher temperature during Jan–Feb months. Analysis of the data was done taking the frequency of occurrence of (4°C and above) difference of temperature between the three consecutive months as a basis for evaluating the shift of elevated temperature towards cooler months Jan–Feb. Analyses revealed that the frequency of occurrence of this temperature differences was maximum in February–March (avg.55%) and March–April (avg.30%) during previous three decades (1961–90). But, such trend was not evident in the recent one and a half decade (1991–05) where the frequency of occurrence of (4°C and above) difference in minimum temperature shift towards colder months i.e., January–February (from 14% to 31%); February–March (from 55% to 46%) and March–April (from 32% to 23%) (Figure 3).

Relationship between air and water temperature

As fish live in water, temperature is particularly important for maturation and breeding of fish. Ground water temperatures integrate annual temperature conditions and are usually within 1–2°C of the mean annual temperature (Meisner, 1990). The data of air and raw water temperature for three years from West Bengal having the similar agro-climatic conditions as that of the raw water of the hatcheries surveyed were analysed. The water and air temperature for three years during the same time period in the last two decades was analysed and a relation was drawn (Dey et al., 2007). A relationship between air and water temperature (monthly means), the equation y = 1.1504x − 3.7305 (R2 = 0.9634) (Figure 4) was used with the recorded air temperature in breeding season months of March to September in the last two decades in 24 Parganas (N) districts to estimate changes in the mean maximum and mean minimum water temperatures. They have increased by 1.7°C, 0. 3°C, respectively.

Shifting pattern of rainfall

Since rainfall is another important criteria that triggers the early maturation of brood fish the rainfall pattern of some of the districts of West Bengal were analysed from the rainfall data (1976–05) collected by IIMT Pune. It showed that the proportion of annual total rainfall occurred in monsoon months (May–August, 68% during 1976–85), but this proportion is gradually decreasing over the time (May–Aug, 65% during 1985–95 & 62% during 1996-05) and increasing in post monsoon months(in Sept-Dec, the proportion increased at 30% whereas this was 23% during 1976–85) at Dumdum (Figure 5) during 1976–05.Similar pattern rainfall distribution were observed at Alipur (Figure 6) district of West Bengal during 1976–05.

Impact on biota (fish)

Data on various aspects of climate and inland fisheries related to the Ganga river system and of aquaculture water bodies (50 Hatchery farms) in its plains covering four districts in the state of West Bengal, India viz. air temperature, water temperature, rainfall, plankton availability, availability of spawn, fish landings etc. were collected and were analysed statistically consulting approximately 200 scientific papers, CIFRI Annual Report (1947 to 2004), Reports of Central Pollution Control Board on water quality of Ganga, Handbook in Fisheries Statistics, Govt. of India, data of IMD, Pune and from other published literature on Ganga river system etc. The entire length of Ganga River, with a span of 2,525 km (the tributaries have a combined length of approximately 10,000 km and the total system is 12,500 km in length) from source to mouth was divided into three main stretches consisting of upper (Tehri to Kannauj), middle (Kanpur to Patna) and lower (Sultanpur to Katwa). Based on the data generated and published over the years that were available, an inference was derived by taking the above-mentioned parameters into consideration in the river Ganga and in the hatchery fish farms located in the plains.

River Ganga

Breeding and recruitment of fish

Fish production in the river Ganga is dependent on the fish recruitment. The fish spawn availability index declined from 2984 ml in the 1960s to 27 ml in recent years (1994 to 2004) (Natarajan, 1989; CIFRI Annual Report-1971–2004) (Figure 7). It also showed a continuing deterioration of Indian major carps seed with decreasing percentage of major carp seed (78.62% in 1961–1965 to 34.48% in 2000–04) where as minor carps (from 20.68% in 1961–65 to 52.95% in 1991 to 1995) and other fish seed (from 0.7% in 1961–65 to 47.8% in 2000–04) showed an increasing percentage in the total seed collection.

The majority of fishes of the Ganga river system breed during the monsoon months, i.e. June to August because of their dependence on seasonal floods, which inundate the Gangetic floodplain areas essential for reproduction and feeding. A decrease in precipitation during the breeding months alters the required flow and turbidity of the water essential for breeding of IMC.

The monthly data of Allahabad from 1974–2003 (Figure 1) revealed that the percentage of total rainfall in the peak breeding period (May–Aug.) declined by 5% whereas it increased by 7% in the post-breeding period when resorption of eggs of IMC sets in.

This shift in the rainfall pattern during breeding season is a major factor responsible for failure in breeding and consequent recruitment of young ones of Indian major carps in the river Ganga.

Predator –Prey Relationship

Clearly any effect of climate warming on the top predators will depend on prey availability and prey fish population. One of the more suitable effects of changes in the thermal structure of an aquatic ecosystem is the impact on the prey densities.

Climate warming may produce a large volume of thermal habitat for the fish and if the same number of prey is distributed across this large volume of habitat, prey densities encountered by a predator would be reduced. Reduced prey densities would reduce the predator encounter rate with prey, which would reduce predator consumption rate.

The predator (large cat fish) to prey (miscellaneous groups of fish and prawns) ratios in the middle (Buxar) and lower stretches (Bhagalpur) have markedly narrowed down from 1:4.2 to 1:1.4 and 1:2.3 to 1:0.9 respectively in four decades (1958-1997) period (Figure 6).

Biogeographic distribution of fish in River Ganga

Surveys reveal that a number of fish species which were earlier never reported in the upper stretch of the river Ganga i.e. from Deoprayag to Kannuj (Menon, 1954) and were predominantly only available in the lower and middle Ganga in 1950s are now recorded from the upper cold-water stretch up to Tehri. Among them Mastacembalus armatus is available between Tehri and Rishikesh and Glossogobius giuris is available in the Haridwar stretch (Sinha et al., 1998).

There is a perceptible shift in biogeographical distribution of the Gangetic fishes. In the Haridwar stretch during the period 1970–86 the annual mean minimum water temperature was 12.9°C (13°C), while during the period 1987–2003 it increased to 14.5°C, an increase of 1.5°C is thus evident. As a result the stretch of river Ganga around Haridwar has become a congenial habitat for these warm water fishes.

Qualitative changes of plankton in river Ganga

The total number of genera of phytoplankton has declined in the last decades with the number coming down from 44 during 1987–89 (Khan et al., 1998) to 42 during 1993–95 (Rachna and Preeti, 2000). The contribution of some genera like Amphicampus, Tetracycles, Diatoma and Ceratoneus has become insignificant in riverine plankton. Temperature is an important environment factors affecting the distributions of diatoms (Ward and Whipple, 1959). Certain genera such as Tetracycles and Amphycampus are usually found in cold mountainous regions, likewise the genera Diatoma and Ceratoneus are often encountered in cool temperate regions than in warmer areas. Here during the last decade's environmental changes due to rise in water temperature resulted in depletion of the stenothermal phytoplankton genera mentioned above.

Breeding of fish in aquaculture farms

During the 1980s in the aquaculture farm hatcheries of the Gangetic plains of West Bengal, breeding season used to commence with the onset of monsoon during June and continued until September. Recorded data in all the hatcheries depicted that the breeding of the Indian major carps started during 24–31 May during 1980; whereas during 2005 all the hatcheries started breeding programmes during mid April. It shows an extended breeding period of 45–60 days, extending the previous season of 110–120 days (Pre1980–85) to 160–170 days (2000–2005).

Interactive response with hatchery operatives and fishers indicate a 90–95% rise in assigned water temperature as the most likely reason for advancement of the breeding period in hatchery farms. The feeling is that this was initially implemented due to the demand and high selling price of the spawn when it became available as early as April.

Growth of Fish

Under controlled laboratory conditions, simulating temperature rise in tropical countries like India, the fingerlings of Labeo rohita (1.39 ± 0.01291 g.) kept in different temperatures and ad libitum feeding showed conspicuous responses for their food conversation, food consumption, specific growth and weight gain with thermal variations in ambient waters (Table 2). The fishes at the end of 92 days exposure showed progressive increase in above mentioned values in the thermal range between 29°C and 34°C but the trend reversed with further increase in temperature by 1°C to 35°C. The gain in weight considered as ultimate achievement of all the physiological activities of a living organism and also index for evaluating the physiological efficiency was by 319.16 ± 37.00% of initial in 29°C. With 4°C increase in temperature from 29°C to 33°C the value raised up by 12.29% (358.89 ± 33.00%) and 38.69% (497.75 ± 48.00%) further when the ambient temperature of the fishes was increased to 34°C. The weight gain in fishes exposed to 35°C unlike increasing between 29°C and 34°C showed decline by 30.10% (347 ± 37.00%) compared to that of 34°C (CIFRI, Annual project report (2006–07)).

Temperature changes will have an impact on the suitability of species for a given location. In temperate areas increasing temperatures could bring the advantages of faster growth rates and longer growing seasons. McCauley and Beitinger (1992) predict that for every 1°C rise in temperature the optimum range for the culture of channel catfish will shift. Channel catfish provide good illustration of some of the cost and benefits of higher temperature growth rate and hence per unit area production will increase with increased average water temperature, but about 30°C feeding is reduced and growth slows (McCauley & Beitinger, 1992). Similarly for the Indian Major Carps in the tropical country India up to 33°C the growth rate increases but from 34°C and above feeding is reduced and growth diminishes.

Impact on riverine fisheries and aquaculture

Fish production in River Ganga

The average fish landings in the upper Ganga river (Kanpur and Allahabad) have come down from 119.35 t in 1959 to 78.15 t in 2004. The average fish landing in the middle stretch (Buxar, Ballia and Patna) was 20.58 t in 2004 in comparison to 69.53 t during 1959. In the case of the lower basin there has been an increase to 88.73 t in 2004 from 66.77 t recorded during 1959 with maximum landing being 115.9 t during 1969 and minimum being 47.1 t during 1990.Thus the total average fish landing in the Ganga river system declined from 85.21 t during 1959 to 62.48 t during 2004 (Figure 9) (Jhingran 1991; CIFRI Annual reports 1959–2004; Fish Statistics FAO 1958–76; Ministry of Agriculture, 1958–2006).

Although the annual landing at Allahabad of Indian major carps (IMC), catfishes and miscellaneous have declined over the years, the percentage landing gives a different scenario according to these findings. The percentage of major carps has decreased from 41.4 to 8.3 during the time period 1958-62 to 1996-97. The miscellaneous fish percent increased from 27.1% in 1958-62 to 63.4 % by 1996-97.During the same time period the catfish percentage have increased from 21% to 24.6% (Dey, 1999) (Figure 10 and Figure 11).

A remarkable increase by 274% has taken place in estuarine fish production (Hooghly estuary) between 1964 and 2003 (Mitra et al., 1997) (Figure 12). Winter bag net fishery contributed maximum to the increased fish production. Greater abundance of clupeids, Sciaenids, anchovies, ribbonfish, Bombay duck and prawns substantiated the bag net fisheries.

The decline of the Indian major Carps (IMC) fisheries in river Ganga has been the major cause for decline of fish production in the river. The reduction in the total annual rainfall and its seasonal variation over the years, coupled with water abstraction from the breeding areas of IMC in the river has resulted in breeding failure. This has directly affected fish recruitment. Water quality changes in river Ganga do not seem to substantiate direct relationship with breeding failure of IMC.

Impact on Aquaculture

Inland aquaculture is centered around the Indian major carps, Catla catla, Labeo rohita and Cirrhinus mrigala. These fishes are bred in captivity by the technique of hypophysation and their spawning occurs during the monsoon season (June–July) and extends till September. In recent years the phenomenon of IMC maturing and spawning as early as March has been observed, Temperature is one of the important factors influencing the reproductive cycle in fishes. This climatic factor along with rainfall and photoperiod stimulate the endocrine glands which help in the maturation of the gonads of Indian major carp. In West Bengal the average temperature is on the rise over the last 60 years. The average minimum and maximum temperature throughout the state has increased in the range of 0.1 to 0.9°C and rainfall pattern has changed. Consequently its impact is being felt on the temperature of the inland water bodies and on the reproduction of fish as shown by the investigations conducted by Dey et al. (2007). Indicate the impact of elevated temperature on the breeding of Indian major carps in fifty fish seed hatcheries in four districts of West Bengal, India viz. North 24 Parganas, Bankura, Burdwan & Hooghly. It shows an extended breeding period by 45-60 days with breeding season extending from 110–120 days previously time period (Pre1980-85) to 160-170 days nowadays 2000–2005.

Discussion

India is a major maritime state and an important aquaculture country in the world with third position in fisheries and second in aquaculture. The fisheries sector has high potential for rural development, domestic nutritional security, employment generation, gender mainstreaming as well as export earnings. It has shown a steady growth and hence called sunrise sector as shown in Table 3.

The contribution of this sector to National GDP is 1.04% and to National Agriculture and allied activities is 5.34%. Indian share in global fish production is 4.36% with 9.92% in inland and 2.28% in marine production. The fisheries sector provides direct and indirect engagement to 1.4 million people.

The total demand of fish during 2005-06 was 5.8-6.0 Mt and supply was 6.2 and the projection for 2012 is 9.74 and 9.6 respectively. (Fisheries Div. ICAR, 2006, NCAP, 2006, Kumar, 2006). To meet the projected demand emphasis is on the expansion of Inland Fisheries in general with emphasis on Fresh water Aquaculture. The present production (2006) and the projected production (2012) of Freshwater aquaculture is 2.6 and 5.1Mt respectively. (Fisheries Div. ICAR, 2006). Freshwater aquaculture has grown from a share of 46% in mid 1980s has increased to 80% in recent times and is one of the fastest growing enterprises in agriculture. Success of Aquaculture sector has important implications both in terms of food security, as source of income, for a growing number of people. Consequently any potential direct or indirect effects of climate change need to be taken seriously.

Impact and Adaptation Options in Fisheries in response to climate change in India

Enhanced water temperature

In the fish culture system enhanced water temperature will decrease the dissolved oxygen content in water. Water holds less oxygen at higher temperature as such fish require more oxygen as temperature rises. Increased growth and food conversion and enhanced breeding period in hatcheries will occur along with increased disease incidence. Operationally there will be changes in the level of production with increase in the fish production cost.

Adaptation options: The Indian Major Carps cultured in India maintain their normal metabolic activities up to 34°C. Beyond this temperature growth and food conversion is affected. Since low oxygen is a problem with enhanced temperature substitution with low oxygen tolerant species like catfishes in the culture system is essential. Though Indian major carps and the exotic carps Cyprinus carpio cultured in India are tolerant of low oxygen conditions (Varga and Chowdhury, 1992) they remain stressed physiologically (Dutta et al., 2005).

Floods

Fish culture facilities will be impacted by damage to the facilities, loss of fish stock and introduction of fish predators and disease germs. Operational costs of the facilities will increase.

Adaptation options: To offset the loss of fish due to recurrent floods, provision for continuous supply of seed from fish hatcheries is required. Management practices should emphasize harvesting of fish at smaller sizes and selection of fish species that require short culture periods with minimum expenditure on inputs.

Drought

The impact on the culture system will reflect in reduced water quality and limitation in the culturable water area and volume. As a result there will be loss in fish production.

Adaptation options: Smaller ponds that retain water for 2–4 months can be used for fish production with fish species like catfish and appropriate management practices.

Cyclones and storms

Inundation, flooding and salinity changes occur in the fish culture facilities resulting in the loss of fish/prawn stock and introduction of predators. Operational damage to the facilities occurs with financial loss.

Adaptation options: An early warning system for weather events is essential to cope up with post cyclone management. It is essential to optimally utilize the normal culture periods and maximize fish production and profit by selecting suitable fish species and appropriate cultural practices.

Water stress

In coming years, availability of water will be a major constraint for aquaculture considering its varied users. Impacts on the fish culture facilities will manifest through decrease in water quality, increased diseases, reduced pond levels, and altered and reduced freshwater supply. Operationally, costs of maintaining pond level artificially will increase along with conflict with other water users. Reduced production capacity will occur.

Adaptation options: Aquaculture should be integrated with other farming systems for many fold use and reuse of water areas. The resource of waste water and degraded water should be extensively used with modified aquaculture practices. Smaller seasonal type ponds of (1–4) months can be used for rearing of appropriate species of fish/ prawn. Increasing infrastructure sophistication of hatcheries for assured seed production of 34,000 million carp fry, 8000 and 10000 million scampi and shrimp (post larval) in India.

Conclusions

The effect of climate change can be felt hardest in a country like India, as a sizable fishermen population in India is dependent on the fresh water ecosystems for their livelihood. In order to sustain the ability of fresh water dependent riverine and aquaculture ecosystems to support fish population and biodiversity, adequate water must be maintained. In the climate-warming scenario, it is expected that low flows in rivers would be more severe along with a general water stress. Water demand in coming years by municipal and industrial sectors would increase; substantial increases in withdrawals for irrigation are expected; a growing human population will increase water demand more than will climate warming. The adaptive capacity under such situation will depend on the abilities to implement integrated water resource management approaches.

This implies that a common framework is essential to be created in India at the country level that should be used towards implementing the integrated watershed management strategy starting from Gram Panchayat (village council) to the river-basin level in a unified manner.

Acknowledgements

The authors are thankful to the Indian Council of Agricultural Research, New Delhi, India for providing financial assistance under the Network Project on Impact, Adaptation and Vulnerability of Indian Agriculture to Climate Change in India. Thanks are also due to the anonymous reviewers who helped with earlier drafts.

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