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Manas K. Das

Central Inland Capture Fisheries Research Institute
Barrackpore, West Bengal, India

Das, M.K. 2002. Social and economic impacts of disease in inland open-water and culture-based fisheries in India. p. 333-344. In: J.R. Arthur, M.J. Phillips, R.P. Subasinghe, M.B. Reantaso and I.H. MacRae. (eds.) Primary Aquatic Animal Health Care in Rural, Small-scale, Aquaculture Development. FAO Fish. Tech. Pap. No. 406.


The inland fishery resources of India (e.g., rivers, wetlands, lakes, reservoirs and ponds) have a rich production potential; however, sub-optimal water quality or detrimental ecological conditions have limited their fish production. Although, in general, reports of fish kills are not properly documented in India, outbreaks of epizootic ulcerative syndrome (EUS) initiated establishment of a disease surveillance and monitoring system for the country. Assessment of disease impacts is hampered by inadequate baseline data on fish production and market intelligence statistics. Thus, an economic evaluation of fish losses is also difficult. In this paper, the results of investigations conducted on these aspects are presented, and the socio-economic impacts of EUS are described through a case study made at three levels viz., the producers, the fish traders and the consumers. The extent of fish and monetary losses suffered as a result of EUS are estimated, the effects on fish consumption and trade assessed, and the role of the media during disease outbreaks examined.


The inland fisheries resources of India are noted as much for their heterogeneity in composition as for as their opulent productive potential. India is endowed with a vast expanse of open inland waters in the form of rivers, canals, estuaries, lagoons, reservoirs, lakes, ponds, tanks etc. (see Table 1).

Table 1. Inland fishery resources of India.1

Although the vast and varied inland fishery resources of India have a rich production potential, this potential has not been achieved. The production potential of the major river in India, the Ganga, in its lower reaches, is estimated at 198.3 kg/ha/yr, whereas the actual fish yield is 30.0 kg/ha/yr, and thus, only 15.2% of the potential is harvested (Sinha 1999). At the present level of management, the yield from the Indian reservoirs, on average, is about 30 kg/ha, whereas a production of 50-100 kg/ha can be easily achieved from large and medium reservoirs, while the small reservoirs have the potential to yield 100-300 kg/ha. The floodplain wetlands, commonly called beels in India, have a rather poor yield, 100-300 kg/ha, against a production potential of 1,000-1,800 kg/ha/yr through scientific management. The present average productivity from aquaculture ponds and tanks is 1,830 kg/ha/yr against a much larger potential.


Most of the rivers and their tributaries, the floodplain wetlands (beels and bheries), and the lakes, reservoirs and small water bodies have either sub-optimal water quality or detrimental ecological conditions that limit their production. The rivers, due to water extraction, siltation and, in many cases, sewage or factory effluents discharge, have become degraded as fish habitat, and quite obviously, there is mortality and decline in fish production. There are various reports of fish mortality from the different regions of the country (Table 2).

Table 2. Reports of mass mortalities of fish in India.

The floodplain wetlands (beels and bheries), the second-most important inland resource in India, are located in the states of West Bengal and Assam, and are mostly in various stages of eutrophication, the majority of them choked with submerged or floating vegetation and having sub-optimal water quality (Sugunan and Bhattacharjya 2000). This has affected the general fish health condition, and most fishes are stressed and have retarded growth. The water quality of Garapota Beel, a typical wetland fairly representative of the ecological status of such water bodies in India, is given in Table 3. The dissolved oxygen (DO) level is reduced to nearly 3.5 mg/L around 10 PM at night, and remains below this level for nearly eight hours, causing stress to resident fish. Moreover, un-ionised ammonia levels are in the range of 0.05-0.25 mg/L, which also act as a stress factor. As a result, the normal growth of fish has been affected, and the average yield of fish from this beel was 550 kg/ha.

Table 3. Physico-chemical characteristics of Ganrapota Beel during 1991.1

In West Bengal, the sewage-fed bheries where fish are reared in nearly 4,000 ha of water area can be cited as an example where, although it is a unique and inexpensive system of rearing fish, the ecological conditions limit the average production to only 1,500 to 2,000 kg/ha (Patnaik 1990). A picture of the water quality in these bheries is presented in Table 4 to emphasise the point that the water quality is creating stress to fish. Here the high microbial consumption of dissolved oxygen (1.8 mg/L/hr) indicates exhaustion of DO for a few hours at night, creating stressful conditions for fish. Moreover, un-ionised ammonia levels are also high.

Table 4. Environmental parameters of sewage-fed wetlands (average values).1


At the very outset, it must to be mentioned that reports of fish mortalities occurring in the water bodies of India are infrequent. The reason for this inadequate reporting is that the monitoring of such information has yet to find a place in the framework of fisheries management practices prevailing in the country. However, with the outbreak of epizootic ulcerative syndrome (EUS), a system of disease surveillance and monitoring was initiated in a structured manner, and reports have been obtained. Table 5 summarised information on the occurrence of EUS in India.

Table 5. Summary Data for outbreaks of EUS in India.

An important investigation of fish diseases in India was carried out by Paria and Konar (1999) in West Bengal in 1994-96. The survey included 17 districts, covering a total of 1,332 impounded water bodies selected at random. Estimates of the prevalences of various diseases seen in the ponds are given in Table 6. The prevalence of EUS ranged from 32.7 to 72.7%; argulosis, from 0.8 to 9.8%; malnutrition, from 10.0 to 32.3%; gill rot, from 8.3 to 34.4%; dropsy, from 3.3 to 14.4%; tail and fin rot, from 2.4 to 10.4%; tumours, from 0.8 to 7.3% and fungal diseases, from 1.1 to 2.2%.

Table 6. Estimates (%) of disease in infected ponds in West Bengal.1

Assessment of the Impact of Fish Diseases in India

One of the major factors limiting assessment of the impact of specific disease outbreaks is inadequate baseline data on the production figures for different fish species caught from inland waters. This weak database on inland fisheries resources has been one of the serious constraints that has plagued the development process. Even market intelligence statistics suffer from various drawbacks due to the disposal of an appreciable quantity of catch directly from the primary producers to consumers. This is precisely the reason that limits evaluation of production losses in India due to disease and other causes. However, a picture of the decline in production due to EUS was obtained from a case study conducted at the Jorhat Fish Assembly Centre in Assam, India to evaluate the damage caused by the disease to fisheries of the Brahmaputra river system (see Das 1994) (Table 7).

The little information that is available from some Indian states on the economic impact of fish losses due to EUS is given in Table 8.

A very interesting and significant investigation by Bhaumik et al. (1991) serves as a case study on the impact of EUS on society in India. Generally, during an outbreak of disease, society is affected at three levels, the producers, the fish traders and the consumers. Thus, it is essential to collect information on the following three aspects: (i) the socio-economic conditions of the fish farmers and extent of suffering caused by disease, (ii) the impact of disease on the fish traders and consumers, and (iii) the role of the communications media in the creation of mass awareness.

Table 7. Species-wise landings (kg) of EUS-affected fish during 1987-91 and percentage increase or decrease (in parentheses) relative to 1987-88 landings.1

Table 8. Economic losses due to EUS outbreak.1

The study was carried out in five districts of West Bengal, involving producers, traders and consumers. Under each district, there are a number of Community Development (CD) Blocks to facilitate developmental activities. In this study, at the producer level, two such CD blocks where maximum water resources exist were selected from each district. A list of fish farmers was prepared, and 500 farmers who were randomly selected from the list constituted the study sample (Table 9). At the trader and consumer levels, the study categorised the data into three sectors: urban, suburban and rural areas. A total of three markets was selected for each, and drawing a sample of 22 from each, a total of 198 fish traders and consumers was selected. All clientele were personally interviewed using a structured schedule developed for the purpose. For assessing the extent of consumption, scores of 3, 2 and 1 were assigned to "most often," "often" and "sometimes," respectively. To study the role of communications media in the creation of mass awareness of the disease, scores of 3, 2 and 1 were assigned to most "effective," "negligible" and "never, respectively. On the basis of the frequency of the responses given, these were finally ranked.

Table 9. Distribution of a sample of 500 respondents questioned on the occurrence and impacts of epizootic ulcerative syndrome.1

Extent of the effect of EUS

The fish species most severely affected by EUS were predominantly bottom-dwelling fishes, like murrels and air-breathing catfishes; other miscellaneous fishes (Puntius sp., Nandus sp. etc.) were also affected. It is interesting to note that in all ponds under a traditional system of culture where both desirable and undesirable varieties of fish occur, murrels were affected at the first stage of the outbreak, followed by miscellaneous fishes and finally by the carps. In scientifically and semi-scientifically managed ponds where piscicides were used to control predatory fish, the carps were affected at the start of outbreak, since no other fishes were present (Bhaumik et al. 1991). The respondents also reported the presence of the disease in more than one species in their ponds. Thus, the pooled data for traditional, semi-scientific and scientific culture operations (see Table 10) indicate that the effects of EUS were maximal on carps (311 responses), followed by miscellaneous fishes (300 responses), catfishes (191 responses) and murrels (186 responses). The effect on carps appears to be most pronounced here due to the fact that most of the ponds belong to the semi-scientific and scientific management categories where the total population of fish cultured consists of carps, whereas in the traditional system carp comprise only a fraction of the total fish cultured.

A maximum number of respondents (154) indicated that the amount of fish lost was between 31 and 40% of the total crop (Table 10), while mortality of the fish crop was reported from the ponds of 17 respondents; in other words, no fish could be harvested from these ponds (Bhaumik et al. 1991). The pecuniary loss suffered by the affected fish farmers was most frequently in the range of Rs 1,001 to 5,000 (213 respondents), followed by Rs 5,001 to 10,000 (72 respondents) (1 US$ = Rs 31). A number of respondents (17) expressed that during the rest of the season they had to search for alternative sources of livelihood, since they had completely lost their fish crop. All of the respondents univocally expressed the need for financial assistance to restore aquaculture and to get relief from the losses incurred due to the disease.

Table 10. Extent of the effect of epizootic ulcerative syndrome on the 365 respondents who reported disease outbreaks.1

Effect of epizootic ulcerative syndrome on fish consumption

Table 11 indicates that a maximum number of respondents (88) consumed fish "often" in the sampled areas. The consumption behaviour before the outbreak was found to be maximal in the suburban sector, followed by the urban sector and the rural sector (scores of 163, 157 and 122, respectively). Most consumers liked carp (115), followed by miscellaneous small fishes (35). Consumers in rural areas had somewhat more affinity for murrels and catfishes as compared to consumers from urban and suburban areas.

The study revealed that the frequency of fish consumption declined due to the outbreak of EUS. Only 15.1% of the sample consumed diseased fish, with the majority of these respondents belonging to the rural sector. The consumption rate was found to be decreased by 28.7, 23.3 and 20.5% in the urban, suburban and rural sectors, respectively. A maximum number of the respondents who used to consume fish "most often" (78) and "often" (88), changed their habit of fish consumption to "sometimes" (90), and their preference was restricted mainly to healthy carps. Most of the respondents declined to purchase even healthy fish when these were kept along with diseased fish in the markets. Again, excepting rural markets, respondents expressed their apathy towards purchase of diseased fish, even if these were sold at a cheaper rate.

A maximum number of respondents expressed that they did not like to consume diseased fish due to "hatred" (120), followed by "fear of transmission of disease" (38) and "unknown fear" (10), even including fear of death. A negligible percentage of consumers showed a change of habit in the consumption of marine fish during the affected period. Thirty-seven percent of the respondents expressed their anxiousness about the disease, and they tried to obtain information regularly from various sources. No occurrence of any disease was reported in the sample of respondents who consumed or handled the diseased fish.

Table 11. Effect of epizootic ulcerative syndrome on fish consumption.1

Impact on Fish Trade

The majority of the respondents experienced a decrease of fish sales in urban, suburban and rural markets owing to the disease outbreak (Table 12). This supports the view of the consumers as explained in Table 11. Moreover, a large number of the respondents (177) did not undertake the sale of diseased fish, as they were concerned about their business reputation (151), "lack of customers" (23) and resistance from the public towards the sale of affected fish (3). Most of the respondents suffered pecuniary loss.

Table 12. Effect of epizootic ulcerative syndrome on fish trade.1

Role of the Media

The study revealed that the fish farmers got the maximum information on the various aspects of EUS from the communications media in the following order: radio, extension functionaries of the state fisheries departments, newspapers, extension functionaries of the Central Inland Fisheries Research Institute (CIFRI), extension functionaries of Comprehensive Area Development Council (CADC), voluntary organizations, television, and publications [see Table 13].

Table 13. Role of communications media in disseminating information about epizootic ulcerative syndrome.1


In India, since, aquaculture or inland capture and culture-based fishery activities are predominantly rural based, the adverse effects of disease outbreaks are felt mainly by the poor fishermen. It is thus essential that adequate attention be given to the management of fish habitat and fish health in India. This would involve firstly, developing trained manpower and infrastructure for fish health research, diagnosis and extension; and secondly, establishing a proper network for dissemination of information on fish disease and fish health management to interested parties during disease outbreaks.


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