This is unprecedented in recent history, experts, fishery officials and fish fry collectors said. These mother fishes usually released spawns every year during March-June, they said.

The non-spawning so far this year might aggravate the gradual extinction of these indigenous species, the frustrated officials and fry collectors said.

A very small quantity of eggs were released last week. Mother fishes released only "samples" this year. Collectors could net a very negligible quantity of eggs.

Halda river is known as the only natural breeding ground for mother fishes for over a century.

"Manmade disaster like indiscriminate netting of mother fishes (egg carrying fishes) and pollution of the river and unfavorable weather conditions are the major causes for the non-spawning this year" said Prof Mohammad Ali Azadi of Zoology Department of Chittagong University, who has been carrying out a research on the unique character of this river and fish spawning.

This river was the main source of fries of Ruhi, Katla, Mrigel and Kaliboush fries for aquaculturists across the country before introduction of fry-breeding in hatcheries in 1980s.

Once natural fries collected from the Halda not only met the country's demand but also were sent to Myanmar and India, they said.

Conditions for natural spawning exists only in Halda in the country. Fishes from spawns in Halda used to migrate to major rivers like Padma and Jamuna, Azadi said.

"Inorganic breeding system in hatcheries results in lessening of the original taste and lead to production of defective fish," Azadi said.

Earlier, around 4000 kilogram of spawns were collected from the river during monsoon but it has declined to about 500 kilogram now, he said.

Prof Azadi who conducted a number of local and foreign funded research projects on natural fish spawning and management in the last 27 years said the government should immediately declare the Halda river a "fish sanctuary" and impose restrictions on indiscriminate fishing to check the "suicidal trend".

Setting up of industries near banks without treatment plants should be stopped to save the river from pollution.

He said the 4500 kilometer long Mekong river that flows through Thailand, Vietnam, Laos and Cambodia is jointly managed by these countries. They have banned fishing in the river for five months during the monsoon to boost fish production in those countries.

District Fishery Officer (DFO) Ershad Meah told BSS that higher authorities okayed a proposal to declare the Halda river from Madunaghat to Satterghat point a "fish sanctuary."

"Now we are considering ways to implement the decision", the DFO said. "We will sit with the experts and stakeholders soon".

The Halda Lover Academics has invented a unique method called 'Plastic Tank Mini Hatchery' to carry fries to long distances, Prof Azadi said. This has ensured over 90 per cent survival of fries.