Shrimp farmers in Khulna, a southwestern district of Bangladesh that grows shrimp mainly for exports, could be facing serious losses this year as the enclosures used for raising their crustaceans are drying up amid an ongoing heatwave.

Besides, poor filtering of the scorching sun is reducing the water's oxygen levels as photosynthesis cannot take place amid high heat in lower-to-middle depths, according to various aquafarmers.

This lack of photosynthesis is also depleting the shrimps' food supply as algae and other organisms consumed by the crustaceans cannot survive in such conditions.

As such, farmers are worried they could face heavy losses as much of their shrimp are dying out despite their increased spending on oxygen tablets and other inputs -- a development which takes place at a time when Bangladesh's shrimp exports are falling for a second consecutive year.

In the July-March period of fiscal 2023-24, Bangladesh exported frozen and live fish worth $298 million, down 21 percent year-on-year, according to data of the Export Promotion Bureau.

The South Asian country, which fetched more than half a billion a decade ago, grows shrimp mainly for the export market on roughly 2.6 lakh hectares of land, data of the Department of Fisheries showed.

Biprodas Bairagi, a shrimp farmer in Chak Shailmari village under Batiaghata upazila of Khulna, said it costs him about Tk 48,000 to release some 40.000 shrimp fry into his enclosure on 50 decimals of land.

"I even dug the enclosure deeper considering the intense heat but still, the water has receded below the acceptable level. I never thought I would find myself in such danger," he added.

Bairagi informed that the water needs to be changed regularly to ensure sufficient oxygenation.

"But there is no water in the nearby canal, so I cannot replenish my enclosure," he said.

Bairagi also said that other than oxygen tablets, he is having to use a water aerator machine round-the-clock in order to maintain sufficient oxygen levels.

The costs compound even further though considering how the farmer has to use a generator to power the aerator in absence of electricity.

"So, counting the oxygen tablets, fuel for the generator and electricity bill, I have already spent an additional Tk 20,000 so far this season," he said.

"If this situation continues, there is no way out of total loss,'' Bairagi added.

Bangladesh has been facing a heatwave for more than three weeks, with the southwest region being among the worst affected areas.

Farmers in adjoining areas are facing the same struggle, with those in the Batiaghata, Dumuria, Dacope, Paikgacha and Koyra upazilas being the worst affected.

Gogesh Mondal, a shrimp farmer in Uttar Bedkashi union of Koyra upazila, said he released shrimp into his enclosures across 10 bighas of land just 15 days ago.

But over the past few days, he found hundreds of dead shrimps floating in the water, which has now become contaminated due to their decay.

"I collected the fry from local sources for Tk 800 per hundred while other costs included buying food and nutrition. Now though, I have lost all hope because of this terrible heat," he added.

Mondal also said the only way to save his shrimp farm this year is to empty out the enclosures before refilling them again.

"But I don't have enough money for taking such a risk," Mondal added while citing how he has spent about Tk 2.5 lakh so far.

Roughly another 300 aquafarmers in his village are facing similar struggles.

As per sources at the fisheries office in Koyra upazila, there are about 4,000 small and big fish enclosures covering 5,000 hectares of the region.

Joydeb Paul, fisheries officer of Khulna, said the suitable temperature for cultivating shrimp is between 25 to 30 degrees Celsius.

Additionally, the crustaceans can tolerate water salinity of up to 25 parts per thousand.

Pal also pointed out that it is recommended to have at least three feet of water in an enclosure during a heatwave.

"If not, the water heat increases and an oxygen shortage occurs while salinity goes up. The shrimp are dying for these reasons, he added.

Mollah Samsur Rahman Shahin, president of the Fish Farm Owners Association of Bangladesh, said at least 3 lakh shrimp farmers in Khulna are being directly affected by intense heat this season.

"During this time, farmers spent all their money on shrimp farming but most of them have died. If the government does not give big incentives, then shrimp farmers will face huge losses," he added.

According to the local fisheries office, shrimp is being cultivated on 144,600 hectares of land across the Khulna, Bagerhat and Satkhira districts.

As per data of the meteorological department in Khulna, the region's temperature has been hovering around 40.3 degree Celsius on average for the past 10 days.