Around 20 species of indigenous fish have become extinct over the last 10 years for use of current nets, insecticides and chemical fertilisers and depletion of habitats, researchers say.

If the trend continues, nearly 70 percent of the local fish varieties may suffer the same fate in the next fewyears, they warn.

Around 100 out of 143 local fish species are in imminent danger of extinction, reveals a study conducted by Dr Mostafa Ali Reza Hossain, professor of fisheries biology and genetics at Bangladesh Agriculture University.

“Some will cease to exist even in the next two years unless measures for their conservation are taken immediately,” observed Mostafa Ali.

According to the study, the species that have already gone extinct include gutum, korika, bhol, debari, one kind of puti, ghora mukhya, nandil, kursa, bhorkhol, ghorpoiya, one kind of tengra and kajuli, torrent catfish, kani tengra, chhoto koi and tilashol.

The fish that face extinction within a couple of years include balichata, betangi, rani, chela, darkina, pathorchata, joiya, ghora machh, baitka and mohashol.

Syed Arif Azad, aquaculture officer of the fisheries department, said excessive use of chemical fertilisers destroys breeding and rearing grounds of the fish.

Fish habitats have been disappearing fast also for people moving in to build houses and other structures.

In fiscal year 2008-2009 alone, over 30 lakh tonnes of chemical fertilisers and 45,000 tonnes of insecticides were used in farmlands across the country, according to Department of Agriculture Extension data.

Rains wash away nearly 25 percent of these fertilisers and insecticides to nearby ditches, canals and wetlands. This instandy destroys the

natural habitats of fish species.

To make matters worse, excessive fishing and encroachment of water bodies continue unabated.

"The basic problem is that there are too few fishes being chased by too many people," said William Collis, regional director of World Food Centre, an affiliate to Consultative Group on International Agricultural Research (CGIAR), a global body.

"Fish are long-term resources," Collis said. "They need permanent protection, and to ensure that, a country needs long term plans to protect its wetlands."

However, things are not all bleak. The government has established a number of sanctuaries across the country to restore fish habitats and maintain fish diversity, said Arif Azad.

MostafaAli said sanctuaries are the most effective and efficient tool for protecting fish. But the problem lies in having proper guidelines on how to build and manage the sanctuaries.

"Sperm banking for fish has to be set up to protect the fast depleting species," he added.

He also stressed intensifying and expanding the Integrated Pest Management (IPM) programme to save crops from pest attacks and combat environmental degradation caused by pesticides.

The IPM is a system of protecting crops from insects without using insecticides.

On crossbreeding of fish species, Arif Azad said it threatens diversity of fish, as it could strip the local fish species of their original features.

The existing fish policy is being reviewed, and crossbreeding of fish might be banned, he said.