Inland fisheries comprise about 80 per cent of the total fish production of the country. Kaptai Lake, with an area of 68,800 ha, is one of the important water bodies. A large quantity of fish is produced every year from this lake. According to the Bangladesh Fisheries Development Corporation (BFDC), total fish production of the Kaptai Lake was 4,556 metric tons (MT) in 2002-03 which increased to 9,364 MT in 2015-16. Over the last 15 years, fish catch from this lake has been increasing steadily. Small indigenous fish and catfish are the prime species.
The Bangladesh Fisheries Research Institute (BFRI) estimates that initially major carps (rui, catla, mrighel, etc.) dominated the catch - about 81 per cent in 1965-66. However, during the last 42 years, this percentage has declined to about 5.0 per cent. In spite of stocking of a huge number of carp fingerlings in the Lake per year, there has been an alarming decrease in these species. On the other hand, the production of small fishes like chapila and kachki has increased to 90 per cent of the total catch now.
Natural breeding of major carps in Kaptai Lake was reported for the first time in 1983-84 and afterwards it was reconfirmed by the BFRI in 2015-16. Yet again, a research project was conducted by the BFRI for confirmation of the spawning locations of major carps considering four natural breeding grounds (Kassalong, Karnaphuli, Chengi and Rhynkiong channels). At this stage, it is very difficult to pinpoint the factors which are responsible for continuous failure in breeding of major carps in Kaptai Lake.
Reproduction of major carp fishes in Kaptai Lake is facing problems. Parts of initial favourable spawning areas have been destroyed either by sedimentation or by fluctuation of water level.
Fish production from Kaptai Lake is reported to have declined due to lack of optimum flow of water and siltation which reduce the rate of water flow and cause habitat degradation, loss of spawning ground and decline of natural seed production of major carp fishes. Cumulative effect of brood stock destruction due to late closure and early start of fishing without following appropriate ban for years is considered to be the major causes of brood (mother fish) stock depletion. Measures for protection and control of these are still inadequate and risky.
Brush shelter is a method of fishing which is employed to trap fishes using branches of bushy trees. This method is locally called 'juk fishing'. About 10-12 years ago, brush shelter fishers comprised only a minority of the total fishing community but now 'brush' is a major fishing method in Kaptai Lake. This method is detrimental to the overall fishery development in the Lake as it involves complete harvesting of all the brood fishes with their progeny. At the same time, most of the fishing gears are found harmful. Fishing by mosquito nets has been destroying small fishes including chapila and kechki. Even stocked fingerlings of major carps are often seen in the fishers' catch. In some areas, fine meshed cloth called chotjal is also seen in Kaptai Lake. Large fish catching nets are seen to have some segments with small mesh nets. Small fries/fingerlings of all species, big or small, are randomly caught and destroyed by these nets.
Impact of increasing local consumers' pressure due to rapid population expansion is found also to be alarming. Since there is no other source of fish in the hilly areas, fishing pressure on Kaptai Lake is increasing day by day. Gradual decrease in average size of the harvested fishes is a clear symptom of biological over-fishing.
Maintenance of water level by the Power Development Board (PDB) is found to be non-friendly for management and conservation of fishery resources. Sometimes, the PDB des not follow appropriate rule of discharge of water from the Lake. It keeps the lowest water level during June-July period which is the peak breeding season and the sensitive period for egg-bearing fishes. As a result, it becomes easier to catch brood fishes in the breeding migration routes due to shallow water depths.
The Directorate of Fisheries (DoF) initially (1961-63) controlled management of the reservoir of fishery. The BFDC has been carrying out fisheries management aspects of Kaptai Lake since 1963. The Corporation runs fish landing stations and ice plants, collects royalty, stocks the reservoir with major carp fingerlings and implements fishing regulations. The Deputy Commissioner (DC) leases the Lake to the BFDC every year. The licence of fish harvesting is given by the BFDC to all the genuine fishermen. The BFRI has been conducting research on various fisheries-related aspects of the Lake for development of a sustainable management approach. Coordination among these departments is necessary to achieve desired production from Kaptai Lake.
To increase fish production of Kaptai Lake, pan and cage culture can play a vital role. Cage/pan culture in the Lake and its ghonas (creeks) has a good prospect. But specific intervention needs some prerequisites: (i) identification of villages and communities who live along the shores of the Lake and are willing to undertake cage/pan culture; (ii) selection of farmers, preferably women, for piloting cage/pan culture; (iii) training of selected farmers/beneficiaries on stocking, low-cost feed production and management, and (iv) technical and financial support for preparing, installing and maintaining cage/pan.
Some steps may be taken to create new ponds and creeks. There is a scope of building creeks in the district for preserving water where it can be used for fish culture. The Department of Fisheries is trying to modernise creek aquaculture activities in Hill Districts and has conducted training programmes for improvement of the existing creeks. Some steps have already been taken to create new creeks for fish culture. The BFRI is trying to adopt fish culture techniques and carry out different research projects on fish production improvement in the hilly creeks.
As availability of quality fingerlings in the hilly areas is a great problem for fish culture. There is a government hatchery at Kowkhali upazila at Rangamati district which is the only source of fingerlings (other hatcheries in the district are not functioning). Most of the fingerlings are collected by farmers from outside the district. Therefore, the price of fingerlings is high and the quality is not good. Due to lack of quality fingerlings, the fish farmers do not get high yield. In view of these facts, the BFRI has developed a technology named feasibility of carps fry raising in Kaptai Lake creeks. In this method, five-day old Indian Major Carp (IMC) fries are stocked and reared to fingerling size in creeks after 60 days. Findings from these studies might have important implications for enhancing fish production and in designing economically viable IMC seed production under poly-culture management in Kaptai Lake.
Adoption and judicious implementation of an appropriate management practice and utilisation of alternate fish production options can increase annual fish production of the Kaptai Lake from 9,500 MT to 20,000 MT. However, for obtaining sustainable production of fish, it is necessary to restore fish habitats and migration routes and conserve fish biodiversity and fish population. Indeed, this is a pre-condition for developing a comprehensive management plan of Lake Kaptai.
The writer is Senior Scientific Officer, Bangladesh Fisheries Research Institute, Riverine (Kaptai Lake Fisheries) Sub-station, Rangamati.
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