Broodfish are dying from traumatic injuries in the Halda river—Bangladesh’s largest natural breeding ground for carps.
Halda researchers and local spawn collectors attributed the deaths to engine-run boats and dredgers engaged in extracting sand from the river.
The repeated incidence of fish deaths, particularly during the spawning season, have turned out to be a big cause for concern for local spawn collectors.
In 2010, the government had declared 40km of the Halda river—from Nazirhat to Kalurghat—as a sanctuary for aquatic animals.
Plying of mechanized boats in the river is prohibited between March and July every year.
From April to May, different species of mother fish, like the catla (South Asian carp), rui (labeo rohita), mrigal (cirrhinus mrigala) and kalbaoush (labeo calbasu) migrate to the spawning grounds of Halda.
On April 27, a mrigal fish weighing around 12 kg was found floating on the river, and later handed over to the Halda River Research Laboratory to determine the cause of death.
Speculating about its cause of death, Prof Manzoorul Kibria, coordinator of the Halda River Research Laboratory, said: "Three wounds were found on the 104-centimetre-long mrigal fish, which might have died after being hit by the propeller of an engine-run boat or a sand-extracting dredger.
"Unfortunately, the gonad of the 10-year-old fish was found to be full of eggs. The broodfish would have laid them in the river within a few days," he added.
Kibria also informed that the district administration had stopped leasing out the sand quarries following the deaths of 18 dolphins, between September 17, 2017 and February 1, 2018.
"The ban on mechanized boats and dredgers during spawning season should be enforced strictly for the sake of conserving the river's ecosystem. The Department of Fisheries, Department of Environment and local administration should strictly monitor this," Kibria added.
Hathazari Upazila Nirbahi Officer (UNO) Ruhul Amin said they are constantly on the lookout for ensuring a safe spawning environment in the river.
"Recently, we seized 10 engine-run boats from the Halda river. We also jailed and fined three offenders. In most cases, the mechanized boats travel the river at night, making them difficult to apprehend," Ruhul explained.
Azharul Islam, a Hathazari upazila fisheries officer, claimed that they have been regularly conducting drives to ensure a safe environment for aquatic animals in the river.
<Broodfish death toll on the rise>
On April 9, a mrigal weighing 8kg was found dead in the river's Khalifaghona point. Bruises were found on the body of the broodfish. On March 4, a 12-kg catla fish and a long-whiskered catfish were found floating on the river at Gorduara point.
Additionally, the survival of critically endangered dolphins is also at stake in the Halda river.
On April 16, a six-month-old dolphin was found floating at Madunaghat point of the river with scars.
A total of four broodfish were found floating dead on the river between March 4 and April 27.
<A river worth 'Tk800 crore'>
Mahbubul Alam, president of Chittagong Chamber of Commerce and Industry (CCCI), said the livelihoods of a huge number of people, including fry collectors and hatchers, depend on spawn from the river.
"The direct contribution of the river to the national economy is worth about Tk800 crore every year,” he said.
However, he claimed, the river is now in poor condition due to various reasons, including untreated industrial effluent, sand extraction, encroachment and discharge of domestic waste.
"As a result, death of broodfish have now become a regular phenomenon. The natural resource will no longer exist if the current scenario continues,” the CCCI president added.