Kaptai Lake is one of the most important freshwater reservoirs of the country and provides many resources, including fish. The lake is fed by the Chengi, the Raingkhiong and other rivers. However, pollution is destroying this vital habitat.
Sedimentation and pollution are reducing navigability and destroying the lake. Indiscriminate fishing by setting up hundreds of small enclosures to trap fish is affecting the natural fish breeding grounds of Kaptai lake.
In the past, the fish were naturally breed in the lake in Rangamati district. Now most of the natural breeding grounds of different varieties of fish, including carp, have destroyed. Many varieties of fish there have already become extinct.
Many years ago it was possible to catch large fish in the lake, but now it has become a tale. Concerned organisations now spend lakhs of taka every year to release fries of carp and other varieties of fish in the lake to restore its old glory.
Data from the Bangladesh Fisheries Research Institute (BFRI) show that there are only four natural breeding grounds of 'Rui' fish in the lake. Of them, the breeding grounds near the mouths of the rivers that flow into the lake have almost been destroyed.
Experts blame increasing sedimentation on the bed of the lake at these spots for the ruin of the breeding ground.
The Bangladesh Fisheries Research Institute has repeatedly asked higher authorities over the last few years to dredge and clean the lake to protect its natural breeding grounds. But nothing has been done about it yet.
BFRI data reveals that though the production of small fish has increased, the carp variety has decreased a lot.
The data also reveals that there were 75 varieties of fish when this artificial lake was first formed. Of them, there were eight varieties of foreign fish and 67 varieties of local fish. Thirty six varieties of fish were commercially collected from the lake at that time.
However, six varieties of fish have become extinct. These are Silon, the local Sarputi, Ghaura, Baghayer, Mohinibata and the local Pangas. Six other varieties – local Mohashoal, Madhu Pabda, Poa, Fasya, Gulsha and white Ghonia – are now endangered. Six more varieties are gradually decreasing. Those are Rui, Katla, Mrigal, Bacha, Pati Pabda and large Chitol.
Fry of several varieties of fish have been released in the Kaptai Lake over the years. The lake also has grass carp, silver carp, rajputi, tilapia, Kalibaus, mojambica, mohashoal, African magur, bighead carp and Thai Pangas that swam into the lake from adjacent ponds during flooding.
At present, Chapila, Kachki, Kata Mola, Tilapia, Kalibaush, Ayre, bata, pholi and local mola are the most dominant fish species in Kaptai Lake.
Kaptai Lake was created in 1960 when the Pakistan government at the time built a dam on the Karnaphuly River to set up the Kaptai Hydroelectric Power Plant. Government data shows that Kaptai Lake normally covers an area of about 58,300 hectares, but this increases to 68,800 hectares during the monsoon. The average depth of the lake is nine metres and the maximum depth is 36 metres. There are 66 varieties of local fish in the lake.
The records of the Bangladesh Fisheries Development Corporation reveal that commercial fishing started in Kaptai Lake in 1965, five years after the lake was formed. In 1965-66, the carp variety made up 81 percent of the fish in the lake, while other varieties made up 19 percent.
At present, the production of the carp variety of fish has declined to five percent. The production of small fish is 95 percent. Small fish such as Chapila, Kachki, Mola are increasing and carp are decreasing gradually.
The BFDC charges tax for each kilogram of fish collected from Kaptai Lake. At present, 92 percent of the taxable fish are small fish such as Chapila, Kachki and Mola.
Some varieties of Rui fish breed naturally in the estuary of the Maini and Kasalong rivers, and in the Karnaphuli river in the Jagannathchora area of Barkal upazila. However, these breeding grounds are also being destroyed.
The use of current nets is banned in Kaptai Lake, but fishermen often defy the ban. This type of net is sold openly in the local market.
Artist Ranjit Dewan, 68, who is from Rangamati, said that in 1964-65, fishermen used to catch Rui and Katol, weighing 15-20 kg each. But such fish are vanishing from the lake. He added that if this continues, there will be only water and bugs in the lake.
The falling water level is also creating various problems. Only realistic and effective measures can bring back the golden days of Kaptai, and there will be an abundance of fish, he said.
The Bangladesh Fisheries Research Institute has recommended banning fishing for three months during the breeding season, and prohibiting the use of mosquito nets for the first one month of the fishing season. But people openly defy this instruction. Furthermore, they also defy the instruction to release carp fry while netting fish. The BFRI also asked the authorities to impose a ban on setting up enclosures in the lake to catch fish.
The science officer of BFRI's Rangamati office, BM Shahinur Rahman, said pollution is harming the fish in the lake. Pollution at Kaptai Lake is taking a serious turn because of open defecation by slum dwellers and unabated dumping of garbage and waste every day.
Kaptai Lake is also losing navigability because of a lack of dredging. Despite repeated requests for dredging, the authorities have not done anything about it, the BFRI official added.
Commander Asaduzzaman, a former manager of BFDC Rangamati, said it seems that dredging Kaptai lake will be a tough job. In fact, it is not that at all. Only the channels (streams) of the Chengi, Maini, Karnaphuli, Kasalong and Raingkhiong rivers where they flow through the lake, have to be dredged. However, it is very important to do a survey to track the channels exactly, prior to dredging the lake. This is because there are many hills submerged in the lake, and it would be disastrous if the hills were dredged away by mistake.
Towhidul Islam, the manager of BFDC Rangmati, said they constantly monitor the lake to stop people fishing with illegal nets and setting up enclosures to trap fish. They have carried out many awareness programmes to educate fishermen about the harmful effects of catching fish fries.
Rangamati's Deputy Commissioner AKM Mamunur Rashid said it is a big project, but the dredging of the lake will begin soon. The initial paperwork for the project has gone ahead at many levels. The relevant departments of the government are seriously looking into the matter, he said.