Fish diversity declines as safe areas dwindle in Kaptai Lake
Filling up the lake with wastes is destroying the breeding sites of fishes
Sunil Kanti Dey, a resident of Rangamati, relished fishes caught in Kaptai Lake, but he cannot satiate his craving for fresh fishes from the lake anymore as many of the species which were previously available there cannot be found now.
Sunil said, "Even around 10-12 years ago, big fishes like Chital, Mahashol could be found in different points of Kaptai Lake. I used to send fishes from the lake to my relatives across the country. But now we do not find big fishes in the lake, so I cannot send fishes even when my relatives request for them."
Local traders and fishermen said filling up the bottom of the lake with wastes is destroying the fishes' breeding grounds. Meanwhile, the ban on catching fishes in the lake is not effective in preventing the fishermen from catching the fry released by the Bangladesh Fisheries Development Corporation (BFDC) in the lake every year.
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According to the Bangladesh Fisheries Research Institute (BFRI) Rangamati River Substation, the production of big fishes like Rui in the Kaptai Lake in 2002-03 was around 258 metric tonnes, which came down to 53.2 metric tonnes last year.
On the other hand, the production of small fishes in 2002-03 was around 3,400 metric tonnes, which stood at around 7,374 metric tonnes last year.
Currently the lake abounds with small fishes like Kechki, Chapila, Kanta Mailya, Desi Mala abound, while big fishes like Tilapia, Kalibaus Ayr, Bata and Foli fish are also found there.
Other fishes which are found in the lake include Grass Carp, Silver Carp, Rajputi, Mozambique Tilapia, GIFT Tilapia, Mahashol, African Magur, Bighead Carp and Thai Pangas.
According to the latest data from the BFRI, Kaptai Lake is home to 75 species of fish. Of these, 67 species of fish are local and eight are foreign.
Asked about the extinction of various species of fish in Kaptai Lake, BM Shahinur Rahman, senior scientific officer at the BFRI Rangamati River sub-center, said although 75 species of fish were mentioned in the latest official report of the BFRI, not all of them are now found in Kaptai Lake.
"Various species of fish including Desi Mahashol, Madhu Pabda, Poya, Faisya, Tele Gulsa and Sada Ghaniya have disappeared from the lake. Meanwhile, Rui, Katla, Mrigel, Bacha, Pati Pabda and Bara Chital are among the species which are disappearing gradually," said BM Shahinur Rahman.
Meanwhile, the BFDC's recent data mentions 42 species in the lake. Among them, several species of fish are no more found in the lake. For example, the annual account of the fishes caught in the lake does not include species like Shada Ghaniya, Mahashol, Sarputi, Magur, Common Carp, Poya, Faisya, and Kakila fish.
Fishes like Silan, Desi Sarpunti, Ghaura, Baghair, Mohini Bata and Desi Pangas have almost disappeared from the lake.
In the sixties, the Karnaphuli Hydropower Station in Kaptai was built by constructing a dam on the Karnaphuli River. As a result, a vast area in the Rangamati went underwater and created the lake, the largest man-made freshwater body in Bangladesh. The Bangladesh Fisheries Development Corporation (BFDC) started fish farming in the newly created Kaptai Lake.
The Kaptai Lake has been contributing to the fish production and socio-economic development of the local people in Rangamati. About 22,000 fishermen make a living by fishing in this lake.
Hari Jaldash, who has been fishing in the lake for the last 30 years, said, "The big fishes that I used to catch in Kaptai Lake in the past are no longer available. Fishes like Chital, Mahashol, Baghair, and Silver Carp are rarely found in the lake nowadays. Now the lake has become a sanctuary of fishes like Kechki and Chapila. We now mainly catch smaller fishes now."
Destroyed breeding grounds decreasing big fishes
The number of illegal establishments in the lake area is increasing, while the waste from Rangamati town is being dumped in Kaptai Lake, reducing the optimum depth of the waterbody. These are ruining the fish breeding sites there.
Supriya Chakma, chairman of the Department of Forestry and Environmental Science at Rangamati Science and Technology University, said, "Earlier, there were many safe places for fish in the lake, but now the safe grounds for fish have been destroyed due to various man-made reasons including massive fishing, and increase in the presence of motor boats in the lake."
He also said, "Disposal of contaminated waste in the waterbody reduces the taste of fish, reduces its size, destroys natural breeding grounds and renders sensitive fish species extinct."
"At the same time, the lake's size decreases and the fish habitat becomes smaller if grabbing the lake continues and the bottom of the lake becomes filled up. Dumping waste in the lake and erecting illegal establishments must be stopped if we want to save Kaptai Lake and its fishery resources," he added.
Rangamati Nagorik Odhikar Andolan's Member Secretary Jisan Bakhtiar said, "The construction of residential and commercial buildings by grabbing the lake area, and dumping all the city's waste into the lake is putting it at risk. If we cannot stop this now, there will be a difficult situation ahead."
Harunur Rashid, president of the Rangamati Fish Traders' Cooperative, said, "There is a huge demand for big fishes in the market, but these fishes have become rare in Kaptai Lake. The number of big fishes or deep-water fishes has been decreasing due to filling up the bottom of the lake."
Ineffective ban on catching fish is also harming the biodiversity of Kaptai Lake, alleged the traders.
Harunur Rashid said, "If fries are released in the lake during the dry season, they get caught in the fishermen's nets due to the scarcity of water in it," said Harunur Rashid.
The business leader opined that the three-month ban on fishing every year could be extended if necessary. In addition, the BFDC will have to take measures to prevent the fishermen from destroying the fry.
"We want the number of big fish in Kaptai Lake to increase as before. But it is not happening due to lack of adequate supervision of the authorities concerned," Harunur Rashid added.
Lieutenant Commander Touhidul Islam, manager of the BFDC Rangamati Marketing Center, said, "Currently there is an abundance of small fishes in Kaptai Lake. The main portion of our revenue comes from the small fishes. However, we have been releasing fish fry every year to increase the production of big fishes like Rui in the lake."
BFRI Rangamati River Sub-Station Chief and Senior Scientific Officer Md Azhar Ali said, "The average fish production in the lake has increased, but the abundance of big fishes has decreased. We are researching how production of fishes like Carp can be increased as it was in the past."
According to fishermen and traders, fish was produced in five channels of Kaptai Lake earlier but now it is being produced mainly in Kattali-Maini channel in Langdu upazila, while fish production in the other four channels has become relatively low.
They said the breeding grounds in the channels of the Chengi and the Raingkhyang Rivers are almost destroyed as the river beds get filled up, reducing the water flow.
Meanwhile, the natural breeding grounds of Rui in the confluence of Kachalang and Maini Rivers and in Jagannath Chhara area in the Barkal area are being destroyed because of filling up the bottom of the lake.
