Saltwater prawns successfully produced in freshwater

Saltwater of the coastline is the home of bagda chingri or tiger prawns. Farmers channel saltwater into hectares of land to farm these prawns there. Tiger prawns and saltwater are seemingly interconnected.

At least that’s what people have believed for ages. That link however seems to have been severed a bit this time. A local farmer has farmed tiger prawns in freshwater instead of using saltwater.

This farmer named Md Tabibur Rahman Joardar (46), who became successful in farming tiger prawns in freshwater lives in Hasanpur village under Dumuria upazila of Khulna. He has achieved such success through his own interest, effort, experience and relentless hard work.

Not just the tiger prawn, he has also farmed different fish in the same pond at the same time. Farming of Golda Chingri or lobster is going on as well. In fact, he has grown paddy on the same field after fish and prawn by clearing out the water.

According to fisheries officials, this farming method requires the prawn fries to be stored in controlled water having a salinity of 5-7 PPT (parts per thousand) for 15-20 days right at the beginning. Later they are released into the freshwater pond.

Prawns farmed in freshwater tastes the same as that of saline water and cannot be told apart in any possible way. Plus, the growth rate of the prawn farmed in saline and freshwater is also nearly the same.

Tabibur has been farming tiger prawns in his freshwater pond of one acre area for three years. Of these three years, he has achieved maximum success this year indeed. Apart from his own experience he has taken help from the fisheries officers also.

He has had a yield of almost 80 mounds of prawn at the rate of around 32 kilograms per decimal of land, from the pond this time. The prawns gained an average weight of almost 50 grammes in 120 days.

He has made almost double in profit compared to his investments. This farmer believes, with efforts it’s quite possible to produce a mound of prawn per decimal of land.

According to fisheries department records, prawns were farmed in the country on 262,980 hectares of land during the 2021-22 fiscal year. This produced a yield of 287,497 metric tonnes of prawns (Bagda, Golda and Harina).

A total of 30,571 metric tonnes of the prawns were exported that year. As much as 80 per cent of the export volume was consisted of tiger prawns, which is farmed exclusively in saline water.

Khulna district fisheries officer Joydeb Pal is labeling freshwater tiger prawn farming as a promising sector. He told Prothom Alo that tiger prawn farming requires channeling saline water onto the farming land causing harm to the environment.

Gradual decline in prawn farming land has resulted in a reduction of production and foreign earning also. In that case, successes in farming tiger prawn in freshwater would be able to play a huge role in the conservation of environment.

Once, the river Hamkura used to flow through Hasanpur village but not anymore. Since the river has dried up, farmers cannot channel saline water into their ponds now. And the tiger prawn farming has been hit hard by this. Tabibur then took a different path.

It was the year 2019, along with lobster fries Tabibur released 2,000 fries of tiger prawn in a freshwater pond. Prior to that, he trained them for 15 to 20 days to make them capable of surviving in saline as well as freshwater. 

He created a small tank inside another pond, using polythene sheets and made the water saline by mixing market-bought salt in it. Tabibur was left with 150 to 200 tiger prawns that year. This excited his interest even more. So next year, he released 20,000 tiger prawn fries in the pond and had a yield of 8,000 to 9,000 prawns after four months.

Later in 2021 he took full preparation to produce tiger prawn only, excluding the lobsters. After readying the pond, he released 50,000 tiger prawn fries there. Nearly 32,000 of them had survived. In 2022, he produced 27 mounds of tiger prawn from 50,000 fries at the first attempt.

But in the second try that year, he faced a huge setback after releasing 250,000 fries in the pond. His aerator (a rotating device used for increasing oxygen) broke down leading to the deaths of those prawns and a loss of nearly Tk 500,000. But this year, he has produced almost 80 maunds of tiger prawns in that pond from 80,000 fries.

Tossing prawn-feed into freshwater pond produces a sort of green plankton in the water, which is harmful for tiger prawns. Taking advice from the fisheries officers, Tabibur released other fish including Rui and Katla in the pond to devour the planktons. There was no harm done to the prawns after that.

Once the prawns are fished out, he will release lobsters into the pond. Farming of other fish will also continue alongside. After farming lobsters till November, he will dry out the pond and then plant BRRI paddy there. He will then harvest the paddy within March and dry out the pond entirely to prepare it for prawn farming again. 

Tabibur said that the food requirements of tiger prawn are different as well. The have to be given salt-mixed feed twice and normal feed once every day.

Tabibur arranged for the tiger prawns to be fished out of the pond on 26 August. Visiting his Joardar Fish Farm that day, a pickup truck was found parked at the end of the paved road.

The pickup was filled with stacks of plastic crates, brought to transport the prawns. Right beside the pickup, a spot had been readied by laying tarpaulins to pile up the prawns. The farm’s a bit further away from that spot.

Going near the pond, around 50 labourers were found busy in work. Some of them were pulling nets, some collecting prawns from the nets while some others were rushing off to the paved road carrying crates full of prawns over their heads.

A pair of aerator devices was still running on the south-eastern side. Rui and Katla, weighing at least 1.5 kilograms each, wriggled inside the net. Meanwhile, 55 mounds of tiger prawns were fished out.  

Hearing the news of freshwater prawns being collected from the pond, Dumuria upazila fisheries officer Abubakar Siddique had come to Tabibur’s farm that day. The official on that day had examined the pond’s salinity level using a refractometer. And, the test showed a salinity level of 0 PPT.   

Senior scientific officer at Bagerhat shrimp research station, HM Rakibul Islam told Prothom Alo that tiger prawns are usually produced in water with salinity level of 5 to 18 PPT.

In that case, if these prawns can be produced in 0 PPT water, it’s better for everyone. In fact the environment will also be saved from salinity, he added.

On 26 August, another fish farmer named Avijit Biswas had come to visit Tabibur Rahman’s farm. He has a saline water tiger prawn farm in Kanaidanga village of Bhandarpara union in the same locality. He was amazed to see tiger prawn being produced in freshwater like this.

“I had never imagined that tiger prawns can be produced so well in freshwater. From next year I will also try adopting that technique,” said Avijit.