B.K. Das and U.K. Sarkar
Considering the fact that the marine capture fish production is almost stagnating, the bulk of the 16 mmt domestic demand of fish by 2025 is expected to come from freshwater aquaculture.
Fish is an affordable and rich source of quality animal protein to mitigate malnutrition and this sector provides livelihood to more than 20 million fishers and fish farmers.
The Gross Value Added (GVA) of the fisheries sector during 2018-19 was Rs. 2,12,915 crores and constituted 1.24% of the total National GVA and 7.28% share of Agricultural GVA.
The sector has immense potential to double the fishers and fish farmers’ incomes and it has shown an average annual growth rate of 10.88% during the year from 2014-15 to 2018-19.The fish production reached an all-time high of 137.58 lakh metric tons during 2018-19.
India is blessed with vast inland open-waters aquatic resources offering enormous scope for fisheries development through knowledge-based scientific management.
In the context of increasing demand, fish production from these inland open-water bodies needs greater thrustnot only for providing quality fish butalso for ensuring livelihood to the fishers and rural underprivileged ones.
It is a matter of concern that most of these waters are in a process of degradation due to increasing anthropogenic activities, impacting several ecological services includingfisheries. This necessitates proper resource management through scientific and technological interventions for sustainable fisheries development.The untapped potential of inland open water fisheries resources yet to be harnessed in a sustainable manner through expanding technology and up-gradation, and plannedscientific interventions.
Resources and it’s Potential
The fish production systems in the open-water resources can be classified in to capture fisheries of the rivers, estuaries and backwaters, and culture-based fisheries in reservoirs, lakes and floodplain wetlands.
The network of Indian rivers with a combined length of 29,000 km comprising 14 major rivers, 44 medium rivers and innumerable minor rivers and rivuletssupport one of the richest biodiversity resources in the world. Wetlands perform many important ecological functions and are considered to be the most productive ecosystem.
Wetland also plays an important role by providing breeding and nursery ground for several fish species. Reservoirs arethe largest and most potential inland fisheries resource, classified as small (<1000 ha), medium (1000-5000 ha) and large (>5000 ha) for management purposes. In India, the area under reservoir fisheries has been estimated at 3.42 million ha (19,386 numbers).The area of small, medium and large reservoirs in the country are estimated to be 16,77,683 ha, 5,27,815 and 13,11,703 ha respectively. The addition of nine proposed reservoirs (99,917 ha) in seven states will further raise the total area to 3.51 million ha. The major riverine resourcesare estimated to yield 0.64 to 1.64 tonnesof fish per km with an average of 1tonne/km, however,production is gradually declining due to various factors and issues. The present average yield from reservoirs is around 120kg/ha/yr, which is only about one third of its potential while in the case of floodplain wetlands, the average yield is around 400kg/ha/yr against a potential of 2000 kg/ha/yr, leaving huge scope for fisheries enhancement.
Major Issues and Threats
Inland open waters in India although possess a huge potential, but are also subjected to several issues requiring focussed attention for sustainabledevelopment of fisheries and conservation of biodiversity.Management of multi-stake inland open water fisheries resources are often subjected to conflict situations due to differences in interests among the stakeholders, policies, geographical advantages, economic implications, politics etc. Similarly, the reservoir also faces certain challenges like scattered distribution, diverse management regime, lack of application of scientific knowledge, weak governance and policy support, creating hindrances in realizing their fish production potential.
Global climaticvariability and change is recognized as a threat to inland open waters,especially shallow water bodies, and future efforts to restore and manage these resources will be more complex. The impact of climate change on ecosystems depends upon temperature and water availability through run-off in the inland freshwater bodies and on sea level rise and storm surges in coastal areas.
Impact on fish biodiversity
Overexploitation, water pollution, flow alteration, degradation of habitat and invasion by exotics are the prominent threats to biodiversity. Over-exploitation and illegal fishingby capturing brooders and juvenile fishes lead to loss of diversity. Water pollution from domestic and industrial point sources poses a potential threat for fish diversity where excessivenutrient enrichment and other toxic chemicals have an impact on the biology of fishes.
Sustainable Fisheries Management
The Inland open-water sector providesconsiderable scope for the enhancement of fish production without deteriorating the ecological and biological integrity of the aquatic ecosystem.Stock enhancement/culture-based fishery is the most important eco-friendly options for sustainable fish production from inland water bodies. Enclosure culture in the form of cage and pen is an effective technology for seed raising and table fish production. Conservation of the fish diversity and restoration of the fish habitat is also animportant management option for river fisheries management.
Wetlands and reservoirs fisheries management
The basic management for a sustainable enhancement of reservoir and wetlands includes stock enhancement, culture-based fisheries and enclosure culture.
Stockenhancement in medium and large reservoir
Stocking of commercially important, fast-growing species like the Indian major carps to utilize all the available food niches has been proved to be an effective management tool to increase fish yield. In open water bodies, which have lost riverine connection due to the construction of embankments and siltation, natural fish stocks of commercially important fish species have been depleted due to disruption of the auto-stocking process from the main rivers. In such cases, stocking with fingerlings of required fish species is found to be effective for increasing their fish yield. The main objective of the stock enhancement is to enhance the self-recruiting fish populations.
Culture-based fisheries in small reservoirs and wetlands
The main scope of culture-based fisheries is to increase the fishyield when recruitment of desired species is lower than the carrying capacity. In culture-based fisheries, fish growth is dependent on stocking density and survival is dependent on the size of stocked fish. The success in culture-based fisheries can be achieved by stocking at the right size, time, stocking density, fishing effort, size at capture (species dependent), selection of species and fishing gear.Over the years ICAR-CIFRIhas provided technological backstopping for reservoir fisheries management in 21 States which resulted in a substantial increase in average reservoir fish production in the country. As a result of stocking, the average fish production of 2300 reservoirs enhanced from 20 kg/ha/year to 110kg/ha/year. Production levels of 1000-1500kg/ha/year have been demonstrated in beels in many parts of West Bengal.
Enclosure culture (pen and cage culture)
In an enclosure, culture fishes are reared in confinement to raise fish seed and grow fish to marketable size throughthe maintenance of free water exchange. Cage and pen have good scope for the production of table-size fish thereby increasing the productivity of reservoirs and wetlands.In situseed raising in an enclosure is a viable and cost effective option to aid fisheries enhancement in wetlands and reservoirs.Technologies developed on cage culture have been applied successfully in many reservoirs in different parts of the country.With cage technology, the states like Jharkhand and Chhattisgarh could able to produce 40-70 kg/m3 Pangasianodonhypopthalmusin different reservoirs. At present in India, a large number of cages (20,000 nos) have been in a functional mode in different reservoirs of 20 States of India.
Assessment of food web dynamics givesimportant information on the ecosystem status and are widely used in ecological studies. The Foodwebis highly dynamicandvulnerable to change. Ecological models ranging from the conventional predator-prey models to more recent ecosystem-based models have been developed for understanding ecosystem structure and function. Mass balance models (Ecopath with Ecosim) have been developed and validatedby ICAR-CIFRI in peninsular reservoirs. Recently a three-dimensional model has also been developed for recommending the optimum stocking density and size at stocking in a reservoir of Kerala.
Ecosystem and species vulnerability
Climatic and environmental parameters are important in regulating reproduction cycles in fishes. At present,there is an inadequate understanding of complex relationships between the physiology of fish and environmental cues in natural open waters. Importance and direction of influence of environmental factors with reference to reproductive ecology need to be established for important keystone species to speculate habitat suitability and formulate conservation plans for the future.
Way forward for wetland and reservoir fisheries
The effective fisheries management in wetlands and reservoirs needs several technological and managerial interventions viz., priority on seed production and seed raising infrastructure in reservoirs and wetlands; refinement of the technology in different agro-climatic condition; appropriate governance for avoiding conflictsamong the fishers and other stakeholders; diversification of species in enclosure culture; development of private public partnership; provision for post-harvest processing and value addition and their linkage to markets; modeling for ecosystem-based management interventions; formulation of adaptive strategies for climate smart inland fisheries; and capacity building.
The riverine resources spreading of the country have beenthe principal source of fish of diversified species for ages. The productionand also the fish diversity, however, have been declining due to several factors like pollution, over-exploitation, destructive fishing methods,entry of exotic fishes, etc. Proper management of riverine fisheries and conservation measures, therefore, is quite vital for sustainability.Some of the recommended programme for the restoration of riverine fisheries and ecology include river ranching, habitat restoration, pollution abatement, creation of fish passes, closed season, protected waters, maintenance of maximum allowable catch and regulation of fishing gears, dissemination of responsible fisheries awareness to the fishermen, introducing of a new concept like environmental flow, and bioremediation for the control of pollutions, etc.
The main purpose of the river ranching programmes is to revive the threatened and depleting indigenous fishes by introducing fish seed to the natural environment. The fish seed may be procured through artificial breeding or wild seed collection from the same rivers system. During the ranching programme, utmost care must be taken to avoid genetic pollution. The ranching sites on a stretch should be designated and fishing in the immediate vicinity shall be regulated after the release of individuals into the river so as to ensure the better survival of ranched fishes.
Habitat protection and fishing ban season
Habitat protection in a river system is an effective management practice to conserve the fish diversity and to develop the overall fisheries of the river. The restriction of fishing and other anthropogenic activity in the protected area provides a natural environment for fish breeding and growth of juveniles. Deep pools in rivers can be declared as sanctuaries that are found to harbour a variety of speciesthat can act as a seed multi-store for a river stretch. Such habitat protection in a river system is an effective management practice to conserve fish diversity.Ban season is another type of management measure for conservation of fish diversity and for the development of fisheries by prohibiting fishing activity, especially during the breeding period so that the recruitment activity of fish may not be hampered.
Pollution abatement and e-flow assessment
Industrial and domestic wastes are the main sources of pollution in rivers. Effluent treatment plant (ETP) and sewage treatment plant (STP) installation in major cities and towns along the rivers is essential for pollution control. Alteration of the natural flow regime of a river can disturb the entire river ecosystem resulting in the breakdown of the riverine fisheries and fish diversity. Thus, proper assessment of e-flow requirement of the river is essential for fisheries management.
Way forward for riverine fisheries management
The sustainable management of riverine fisheries resources requires focused programmes through identification and protection of breeding ground in the river ofthreatened species for conservation; protection and conservation of breeding ground of commercially important species for stock enhancement; proper governance for effective management of riverine fisheries; adoption of community based approach for fisheries management and biodiversity conservation in the river; application of GIS and remote sensing technology for resource mapping for sustainable utilisation of resources from river.
Recent Technological Advances in Inland Fisheries
ICAR-CIFRI, a premier institute working for the research and development of inland open water fisheries, and several other governments and non-governmental organisations have associated in development and refinement of technologiesand management strategies for inland open water fisheries over the decades, commercialized cage grow feed, CIFRI GI cage and CIFRI HDPE Pen. The details of some important ones are as follows:
- Cage culture: Technology developed for raising table fish for exotic pangas catfish (Pangasianodonhypophthalmus) in reservoirs in cages with the production of 40 kg/m3/8 months.Successful trials carried out and assessed performance for several other species in cages in reservoirs /wetlands viz., Ompokbiamculatus, Labeobata, L.rohita,Jayantirohu, L. gonius, PuntiussaranaandBarbonymusgonionotusandHeteropneustesfossilis.
- Electronic data acquisition system (eMATSYA): Electronic Data Acquisition System using the android application (in multilingual) to capture real-time fish catch data through mobile phones was developed.
- Biocontrol of biofouling in cages:Feasibility of polyculture of these species in cages has also been explored. Inclusion of 20% herbivore fish P. gonionotus with Pangasius has also been found not only to increase overall production but also effective as biocontrol against algal biofouling.
- Low-cost floating fish feed for cage culture: Using agro-industry co-products, a lowcost feed with highly stable floating feed with FCR (1.3) has been developed for P.hypophthalmus. It saves feed cost by Rs.10-12/kg compared to commercial feed with similar protein content for P.hypophthalmus. Similarly, a sinking feed with high water stabilityhas also been developed.
- Application of acoustics for reservoir fisheries management: Acoustic technology was utilized for the identification of Potential Fishery Zones (PFZs) in reservoirs. This technology is expected to increase fishing efficiency and reduce fishing cost.
- e-flow estimation: e-flow requirements were assessed for river Dri, river Tangon, river Teesta, river Mahanadi and river Cauvery.e-flow requirements for the breeding of some of the species like Rita ritaand Tor putitorain river Mahanadi have been estimated.
- Climate change mitigation:Carbon sequestration potential of mangroves in Sunderbans, five wetlands of West Bengal and two wetlands of Assam have been assessed.Thermal toleranceof the 24 fishspecies of Ganga River basin has been documented.Breeding thresholds, pre-spawning fitness (Kspwan50) and climate preferendum have been estimated for ten species from Ganga River basin with reference to climate change. Vulnerability maps have been prepared for wetlands of West Bengal on GIS platform depicting 15-20% shrinkage over due course of time. Trophic status has been studied for 52 wetlands of West Bengal reflecting the mesotrophic to eutrophic nature of most of the floodplain wetlands in the state.
- Hilsa fishery management guidelines: A study in river Hooghly showed 20% over-exploitation of the hilsa stock. At least 20% reduction in fishing effort, along with restriction of <90 mm mesh gill nets and banning fishing of brood fish during the breeding season (June to August) are suggested for the conservation of the stock.
- Valuation of goods and services: Valuation of goods and services of several wetlands was carried out to highlight their exploitation, loss and sustainability.Economic valuation of wetlands and proper impact assessment is crucial for posing these tender ecosystems as national assets.
- State roadmap development:Roadmaps for enhancing fish production from reservoirs through technological interventions including cage and pen culture for Bihar, Jharkhand, Odisha, West Bengal, Telangana,five North Eastern states, and Andaman and Nicobar Islands have been developed by ICAR-CIFRI. Recently Odisha government has initiated pen culture in reservoirs for seed raising targeting 100ha area with technical support of the institute.
Inland open waters are potential resources not only for fisheries enhancement and biodiversity conservation but also for augmenting table fish production through the adoption of available technologies.Stock enhancement in rivers and large reservoirs, culture-based fisheries in small reservoirs and wetlands, cage culture in medium and large reservoirs, pen culture in wetlands and marginal areas of reservoirs, buildingthe capacity of stakeholders, creating value-chain and market links, infrastructure and strengthening institutional and governance instruments are essential for fisheries management in reservoirs and wetlands.The rivers are the repository of invaluable fish germplasm and must be scientifically managed for the conservation of biodiversity. Estuaries require special attention as breeding grounds of commercially important fish and shellfish for conservation.
A view of cage culture activities of ICAR-CIFRI in Maithon reservoir
Fish harvest in ICAR-CIFRI pen
Fish harvest in Palair reservoir, Telengana
Fish seed raising in cages
Participation of women in cage farming
(The authors are Director and HOD of RWF division in ICAR-CIFRI Barrackpore, West Bengal respectively. Views expressed are personal.)