CONTENTS-
Abstract
Fish Mortality in Kerala
Fish Mortality in the Himalayan Region
Lakes in Uttar Pradesh
Fish Mortality in Karnataka - Bangalore City
Management and Conservation
Conclusion
References

Water is an essential component of an eco-system. It sustains life on earth. A community depends on water for its domestic, agriculture and industrial needs. Availability of water has been a factor in the development of various civilisations near lakes and rivers. Lakes and tanks are known to be the ecological barometers of the health of a city. They regulate the microclimate of any urban centre. Rapid urbanisation has lead to the loss of wetland habitat through encroachment, bad management, pollution from sewage, and waste and litter disposal activities. These factors have seriously affected the survival of lakes and have posed serious threat to the flora and fauna supported by them.

Large-scale episodal freshwater fish mortality has been experienced in various lakes throughout India during the past few years. The underlying reasons may vary depending on the specific site but there is a general pattern seen everywhere which points out to the unplanned development, pollution and urbanization. The major causes of fish mortality in various parts of India are briefly discussed here in this paper along with the conservation strategies to be adopted to preserve the fish resources of India.

More and more species of fresh water fishes in the country are facing extinction due to destructive fishing, pesticide runoff and pollution. A recent evaluation of the status of 327 freshwater fishes has revealed that already two species   are extinct, 47 species critically endangered, while 98 varieties belong to the endangered category.

1.1.1 DEVASTATING HUMAN INTERFERENCE

Loss of habitat, human interference and trade were the three most serious threats facing the freshwater fishes. Suitable action have to be taken on a war-footing to ensure the survival of "taxa" and their habitat, otherwise, there is every chance of extinction of more than half-a-dozen species in the near future. The inland water bodies are facing serious devastation due to various human interventions. Unrestricted fishing coupled with the deteriorated environmental conditions have resulted in the depletion of some of the principal species of commercial importance such as milkfishes, bhetki and pearlspot in the estuaries and backwaters and thooli, maryetta, mahseer and attukonchu in the rivers.

Human interventions have also brought about the loss or impairment of the natural habitat of many finfishes and shellfishes. Shrinking of backwaters and rivers at an alarming rate in recent years on account of agricultural expansion, urbanisation and housing has greatly contributed to the depletion of the fish resources.

Fishing wealth of the inland water bodies are dwindling alarmingly due to deforestation, destruction of mangroves, pollution, destructive type of fishing methods, indiscriminate exploitation of spawning   population, threat from exotic varieties of fishes and diseases. Many of the principal fish species of commercial importance are being depleted from the inland waters due to large-scale habitat destruction, over exploitation and deforestation of mangroves. The aquatic pollution is also assuming alarming dimensions as evident from frequent reports about mass mortality of fishes in the inland water bodies adjacent to industrial units.

1.1.2 LAKES IN KERALA :

The inland fisheries sector of the Kuttanad region is ridden with several problems. Meanwhile, due to the massive reclamation of kayal lands for household, agricultural, and industrial purposes, available fishing   areas have declined drastically. In their bid to maintain the size of the daily catch local fishermen work overtime and use large quantities of nets and other fishing gear. Owing to over-fishing, the productivity of the fishing grounds has decreased drastically. Although the use of fishing gear that leads to mass destruction and the premature catching of inland fish are legally banned, such practices continue.

The gradual but steady degeneration of the ecosystem of the Kuttanad region has become a severe threat to its aquatic life. In this respect, the role of Thanneermukkom salt water barrier has been very crucial. During the summer months when shutters of the bund are closed the low tidal effects cease and impurities are accumulated in the southern parts of the Vembanad lake. Salinity in areas lying south of the Bund becomes too low for the growth of prawns and brackish water fish. Migration routes of prawns and fish are also disrupted by the bund. Owing to the dumping of domestic sewage, discharges from factories and accumulation of fertiliser and insecticide residue flushed out from rice fields, the Vembanad lake and the waterways have become highly polluted. The unprecedented outbreak and the sudden spread of the inland fish disease in the water bodies of the Kuttanad region during the early nineties caused mass mortality among almost all the species of wild inland fishes.

1.1.3 EFFECTS DUE TO BORDEAUX MIXTURE:

Copper poisoning was found to be the major cause of the debilitating fish disease ''Epizootic Ulcerative Syndrome'' in India and several south east Asian countries. The main source of copper in the ecosystem was the Bordeaux mixture, extensively used as a fungicide in pepper, coffee, cardamom and rubber plantations (Natrajan and Sehgal, 1982). This important finding was made by a joint research programme of Central Marine Fisheries Research Institute (CMFRI) and the Department of Environmental Science, University of   Kerala.

The research on causes of this particular fish disease   is being conducted for the past 25 years in various laboratories around the world, it was for the first time that it had been conclusively proved that copper sulphate content in Bordeaux mixture make the fish susceptible to various bacterial and fungal attacks.

The fish disease usually occurs under certain   conditions in the lakes and other water bodies in India and the South East Asian countries. The study found that bordeaux mixture got dissolved and reached the water bodies by seeping through the soil during monsoon. Depending upon the acidity of the water, the poisonous nature of copper would increase, affecting the defence mechanism of fish. Consequently, the mucus secretion of the fish would decrease causing fall of scales and making it susceptible to different types of bacterial and fungal attacks. This would create ulceration and cause large-scale mortality among the fish population.

This disease was reported from Pookote lake in Waynad district of Kerala in June 1991. The fungicide was used extensively   to prevent the ''quick-wilt'' disease in pepper, which affected plantations in the district. A team of researchers   from the Department of Environmental Sciences   are continuing further investigations on the subject.

Lakes in Kashmir Valley (state of Jammu and Kashmir), situated at an altitude of 1537 to 1587 m, at the foot of the Himalayas in the state of Himachal Pradesh, are the major coldwater fishing water bodies in the Himalayas (Crowe, 1955). The lakes have a commercial and a subsistence fishery, based on exotic and indigenous fish species. The floodplain lakes in Kashmir Valley are rapidly ageing, with their water area being reduced by encroachment   due to agriculture on lake margins and by a massive aquatic plant growth, which is enhanced by pollution from the surrounding land (Das and Subla, 1970).

1.2.1 LAKES IN KASHMIR:

The lakes in Kashmir valley   are alkaline   (pH 7.4-9.6), the high pH values in summer, the result of an intensive photosynthetic activity from rich phytoplankton. The vertical gradient of dissolved oxygen concentrations differs from lake to lake.

•  In Lake Wular, which is mixed throughout the year, oxygen concentrations do not vary much from the surface to the bottom.

•  Lake Manasbal and the Nagin basin of Lake Dal have a clinograde type of oxygen profile, i.e. with the depth the dissolved oxygen concentration decreases.

•  Lake Dal. has a net positive input of 4.36 t of phosphorus and 39.2 t of nitrogen per annum.

  The lower water layers of these lakes get depleted in oxygen   during the summer,   which indicates that the lakes are eutrophic. This is further confirmed by high concentrations of phosphorus in summer. This is the result of a high input of nutrients reaching the lake from human settlements, hotels and arable land surrounding it (Sehgal, 1988, 1974, Sunder and Subla, 1984, 1984a). Further evidence of high inputs of nutrients in these lakes comes from the extensive cover of aquatic macrophytes. Their distribution depends on environmental conditions such as current velocity, nature of substratum, and the availability of food. Ecological degradation of water bodies and over fishing has led to a decline in fish stocks and large-scale fish mortality (Sehgal, 1970).

1.2.2 ECOLOGICAL SUCCESSION   IN LAKES:

In recent years the increase in land use as a result of intensive agriculture and urbanisation in watersheds has resulted in an increased input of organic waste into rivers and lakes. This has led to eutrophication of some lakes, and pollution of streams. Lakes Nainital and Bhimtal in Kumaon, and lakes Wular and Dal in Kashmir are examples of such an impact. Lake Dal is facing a serious problem of shrinkage. Between 1911 and 1984 the open water area was reduced from 1507 ha to 700 ha, while marshy areas increased form 800 to 1530 ha. 40,000 to 52,000 t of dead aquatic plants and other organic material from intensive agricultural and horticultural activities on the margins of the lake are added annually. Lake Dal is also suffering from the input of domestic waste from anchored boats, lakeside hotels and settlements along its shore. This alarming situation calls for urgent remedial measures if Lake Dal is not to disappear in the not so distant future. Lake Manasbal is also undergoing eutrophication due to the increased input of nutrients from various human sources (Kumar et al. 1982).

Dal and Wular lakes in Kashmir, have especially been adversely affected by pollution and poor management of land in the   catchments. The lakes are undergoing eutrophication and biological degradation. The entire catchment of Kashmir Valley ultimately drains into Lake Wular before the outflowing waters leave India for Pakistan as the Jhelum River. Lake Wular has been reduced in size from 27,500 ha to 15,200 ha, and its mean depth is now 1.5 m, instead of 3 m.

1.2.3 FACTORS CAUSING MORTALITY :

•  There has been a rapid encroachment   due to agriculture, especially rice paddies, on the margins of the lake.

•  Construction of embankments to protect crops against flooding, and planting trees along the margins under a social forestry programme have also contributed to the process of shrinking of the lake.

•  The open lake water area has been further diminished by the introduction of floating islands for vegetable cultivation.

•  The shallowness of the lake has also become a hindrance

•  The changes have also adversely affected fish production and the growth of aquatic plants, which are very essential for sustaining life.

It is believed that the ecological degradation of the Himalayan lakes has not yet reached the state of no return. Even now it is not too late to start conservation programs to preserve our natural resources.

Lakes Nainital, Bhimtal, Naukuchiatal, Khurpatal and Sattal   are situated at an altitude from 1220 to 1937 m, and all are at latitude 29 o N, within a short distance   from each other, and within a 25 km radius of the town Nainital. All lakes are small, with winter mortality as a regular feature.

The water of Kumaon lakes is mostly slightly alkaline. The water stratifies in spring and mixes during winter. Lake Nainital is eutrophic. Bhimtal and Naukuchiatal have moderate levels of nutrients and are mesotrophic. Lakes Khurpatal and Sattal are poor in nutrients. The rising level of nitrogen in Lake Nainital indicates an increasing pollution. The result has been an increase in biological production, leading to a higher organic matter production and its deposition in the bottom, resulting in anoxic conditions in the bottom water layers. In the Kumaon, the growing demands of local residents to meet the challenge of increasing tourism and other development programmes have increased pressure on Lake Nainita (Sehgal and Sar, 1989). Kumaon Himalaya, especially the lakes, has    witnessed   a dramatic increase in recreation. In Nainital, the number of tourists increased from 160,000 in 1958 to 680,000 in 1986. Lake Nainital has been so badly damaged by the input of sewage that it cannot fully recover even if the pollution discharge into the lake is diverted. Fish kill in some Kumaon lakes has now become an annual occurrence (Menon 1954 and 1964).

1.3.1 REHABILITATION OF HIGH ALTITUDE LAKE ECOSYSTEMS :

The high altitude lakes of Kumaon region have become highly polluted due to enrichment and unscientific stocking of fish like Gambusia affinis . Lake Nainital, one of the picturesque high altitude lakes has become so polluted that it experiences episodes of fish mortality a number of times in a year. A comprehensive lake conservation plan using the stocking of environment friendly fish species and aeration of the whole lake system has been prepared to combat the pollution and slowly improve the lake ecosystem (Sarin, 1979). The strategies formulated will completely deutrophy (remove the nutrients) the lake and help in the establishment of ecologically suitable, technically viable and socially acceptable aquaculture in the lakes.

As per the Studies conducted by Benjamin et.al in 1995, Sankey lake,   in Bangalore city, fish mortality occurred on   a large scale during June - July 1995. This episode immediately   followed the fish deaths in Lalbag Lake, which is located about 12 kilometers away. These studies reveal that the fish-kill in Sankey Lake was due to a sudden and considerable fall in dissolved oxygen (DO) levels in some locations caused by sewage let into the lake resulting in asphyxiation. It was found that the large-scale fish mortality was not due to any kind of infection because none of the fishes appeared to show any symptom of disease.

The first step in any management procedure is to assess the existing condition of water in the site. Theoretically it would be impossible to keep all contaminants out of   the water ; even without human influences, contamination of bodies of water has always occurred and will continue to occur. However, this fact does not relieve us of the dangers of water pollution and draws our attention to the means of detecting and avoiding such pollution. This, of course, also necessitates the provision of training and technological know-how.

1.5.1 ASSESSMENT PROCEDURES:

General review of assessment procedures that can be followed are:

1. Physical and chemical water analysis

2. Biological procedures based on the use of:

a) Bioindicators,

b) Biomonitors

3. Remote sensing

1.5.1.1PHYSICAL AND CHEMICAL WATER ANALYSIS :

With the aid of physical and chemical analysis techniques, it is possible to obtain information on the condition of water at the place and time at which the samples are taken. Depending on the quality of the investigation   methods used and the number of parameters studied, some useful data is obtained   on the quality of the water at that point in time. How accurate and detailed the results are, will depend upon the purposes for which analyses are performed. In order to obtain more precise data, repeated analyses are necessary; these can even be aimed at identifying changes during the course of a single day. A number of parameters are measured, including the presence of the amount of organic carbon, ammonium, nitrate, orthophosphate and oxygen, as well as the biochemical oxygen demand (BOD). By means of additional tests, it is also possible to obtain additional information on the concentration of toxic substances. As is to be expected, continuous   monitoring   are associated with high technical, financial and labour inputs. The costs incurred grow with the number of samples taken and the range of substances, which they are tested for. Even the industrialized countries can only afford to do this within certain limits. Nevertheless, within the scope of major technical projects, it would be useful to carry out similar sample-taking and analysis programs at various locations for monitoring purposes. This would have to be specifically decided upon with respect to each individual case.

1.5.1.2 BIOLOGICAL METHODS:

When evaluating water pollution with the aid of bioindicators, an understanding of an organism's reaction to changes in its environment is essential. These reactions can take the form of growth and/or increased population density, modified activity, reduced growth, a decline in population, or even death. Depending on their degree of complexity, size, generation time and other factors, organisms and different species react at varying rates. Most bacteria adapt very quickly to environmental changes. Protozoa and algae take longer, and insects - many of which live for a year or longer as larvae in the same aquatic environment - require longer periods to react to changes in their surroundings. As a rule, organisms with longer generation times respond more quickly to negative changes -if they exceed the limits of what is tolerable - for example by migrating to zones with satisfactory living conditions or by dying. Depending upon the time, which bioindicators or indicator organisms spend in a body of water, they are subjected to the prevailing environmental conditions and any changes that occur. Thus, members of a related group of organisms or a biological community integrate and reflect environmental conditions and possible changes over an extended period of time. Consequently, critical evaluation of the species compositions can yield sufficient data on the situation of a body of water and the range of fluctuations in the environment over a long period of time.

1.5.13 REMOTE SENSING :

Aerial photography can yield qualitative and quantitative information on changes in environmental conditions. Remote sensing can be used to provide information on the environment at a wide   scale. At local scales it can be used to study a small area in considerable spatial detail. Spatial resolution data sets provide valuable data on the environment especially in the context of changes. The studies of this type, which have been performed on the expansion of dry regions (examples: Sahara, Sahel) are well known. Changes in the condition of large bodies of water can be detected in the same way. Studies in South India have shown that satellite remote sensing techniques can provide reliable and objective data on water quality, agriculture productivity and related water management aspects.

1.5.2 CONSERVATION STRATEGIES:

After assessment of the existing condition of water and the possible reason causing fish mortality the next stage is adopting various conservation strategies suited to the particular area. Any conservational strategy includes the management and ensuring the optimum quality of the particular environmental condition, because it is known that the microenvironment causes more effect than an environment found few meters away.

Although conservation measures vary for different species , most   management measures address the factors of decline identified for the fishes such as water quality and quantity, physical habitat,   fish passage and fish screening and fish management. The common measures suited for most species are:

•  Formation of watershed councils and other working groups that allow cooperation and collaboration among interested parties and key actors.

•  Planning efforts that identify and address factors impacting these populations.

•  Monitoring and research that looks at species' life histories, population levels and trends, and factors of recovery and decline.

•  Measures adjusting harvest rates to allow for sustainable escapement levels, or terminating harvest where no harvest can be sustained.

•  Measures modifying hatchery programs, marking hatchery fish for the implementation of selective fisheries, minimising interactions between hatchery and wild fish, or otherwise ensuring the survival of wild populations.

•  Measures providing education and outreach, distributing materials to help with the identification of species of concern, developing educational programs.

•  Regulate the fishing activity currently on as this will most likely assume disastrous dimensions of over exploitation of our fish   resources which in long run would eventually spell the doom for Indian fisheries.

•  Moratorium for a certain period can be imposed on construction and replacement of mechanised vessels

•  Preparing accurate periodical estimates on the status of the country's fishery reserves and deployment of the country's fishing efforts accordingly.

•  Strict enforcement of the marine fishing regulation act and compulsory registration of all types of fishing crafts and gears with a view to have   an accurate statistics on the pressures on fishery resources.

•  Effective legal measures are to be introduced to end the ``wanton destruction'' of the fishery resources and countering the impact of "man-made stresses on the bio-diversity of our waters".

•  A harmonious integration of aquaculture with coastal zone management and adoption of sustainable aquaculture practices with minimum negative impact on environment and bio-diversity

The recent ecological degradation of various Indian lakes and their effect on fish mortality have been discussed. The level of protection or control or regulation required to reach the sustainable and stable condition is dependent on the recovery and restoration of the lake conditions .The remediation for this is the conservation and management of inland fishery resources. These measures are urgently required for long-term sustainability, otherwise these water bodies might transform into aqua deserts in the years to come. Steps are to be taken for the conservation of all the lakes, which not only provide a recreational spot for the tourists, but also   serve   as one of the potential sites for the growth of the major Indian fishes.

Benjamin Ranjeev, Chakrapani,B.K., Kar Devashish, Nagarathna, A.V., and Ramachandra, T.V. 1996. Fish mortality in Bangalore lakes, India, Electronic Green Journal, (International Electronic Journal. URL: http://www.lib.uidaho.edu: 70/docs/ egj.html),   Issue 6, December 96.

Crowe, P. 1955. Trout fishing in Kashmir. J. Bombay Nat. Hist. Soc. 53: 217-28.

Das, S.M. and B.A. Subla. 1970. The Pamir-Kashmir theory of the origin and evolution of ichthyofauna of Kashmir. Ichthyologica 10(1-2): 8-11.

 
Kumar, K. 1988. Gobindsagar reservoir, a case study on the use of carp stocking for fisheries management. FAO Fish. Tech. Rep. No.405 (Supplement): 46-70. FAO, Rome.

Kumar, K., K.L. Sehgal and S. Sunder 1982. General creel census of the two principal trout streams of Kashmir. J. Inl. Fish. Soc. India 14(1): 11-17.

Macdonald, A.St.J. 1955. A fishing holiday. J. Bombay Nat. Hist. Soc. 53: 346-56.

Menon, A.G.K. 1954. Fish geography of the Himalayas. Proc. Nat. Sci. India 20(4): 467-93.

Menon, A.G.K. 1962. A distributional list of fishes of the Himalayas. J. Zool. Soc. India 14(1 and 2): 23-32.

Natrajan, A.V. and K.L. Sehgal. 1982. State of art report on biological behaviour of migratory fishes in the context of river valley projects. Report. CIFRI, Barrackpore. 42pp.

Sarin, N.C. 1979. Protection of fish and its impact on national and international tourism. Indo-lGerman Agric. Project, Palampur, Himachal Pradesh. Special Issue, Newsletter 4(6): 8-12.

Sehgal, K.L. 1970. Report on the factors responsible for large-scale mortality of brown trout, Salmo trutta fario Linnaeus in Chawalgam trout farm in Kashmir Valley. CIFRI/CWF Rep. 7: 10pp.

Sehgal, K.L. 1974. Report on the researches carried out at the Coldwater Fisheries Research Centre in Himachal Pradesh and Kashmir from 1966-1973. CIFRI Suppl. Rep. 13pp.

Sehgal, K.L. 1987. Sport fisheries in India. ICAR Publication, New Delhi. 126pp.

Sehgal, K.L. 1988. Ecology and fisheries of mountain streams of the North-Western Himalayas. Thesis for the award of D.Sc. degree, University of Meerut, India.

Sehgal, K.L. 1990. Report on impact of construction and completion of Beas Project (Stage I - Beas-Sutlej Link, and Stage II - Pong Dam) on limnology and fisheries of R. Beas.CIFRI/NRCCWF. 45pp.

Sehgal, K.L. and C.K. Sar. 1989. Impact of construction and completion of Beas-Sutlej (BSL) Project on coldwater fisheries of R. Beas in Himachal Pradesh. In: National Workshop on Research and Development Needs of Coldwater Fisheries in India, Haldwani, Jan. 1989. Abstract

No.14.
Sunder, S. and B.A. Subla. 1984. Hydrobiological observations in a stretch of river Jhelum, Kashmir. II. Phytoplankton. In: Seminar on Conservation and Management of Fisheries Resources, Jammu. Abstract No.9.

Sunder, S. and B.A. Subla. 1984a. Fish and fisheries of R. Jhelum, Kashmir. Zoologica Orientalis 1(2):34-39.

http://ces.iisc.ernet.in/energy/monograph1/Biblio1.html http://www.seagrant.wisc.edu/greatlakes/glnetwork/toxics.html http://www.co.clark.wa.us/site/esa4/esaact.htm
http://www.glifwc.org/Indian_fishery/manage.htm http://www.expressindia.com/fe/daily/19990422/fec22003.html

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