As ilish population keeps declining gradually, Dhaka Tribune's Bilkis Irani takes a look at why saving the rivers is becoming the only option in this last report of a four-part series
With the ilish population declining day by day in Bangladesh’s rivers, researchers in Bangladesh have been trying to farm the national fish of the country in four phases.
However, their research has only proved that farming ilish commercially in ponds is not yet a viable option.
The government has also been keen to see such attempts succeed as ilish accounts for 1% of the country’s gross domestic product (GDP) and 11% of the country’s overall fisheries production.
Researchers have emphasized dependence on natural resources and urged the authorities concerned to protect the rivers in order to keep the production of ilish thriving.
To know why ilish cannot be farmed commercially and learn how the researchers tried to grow them commercially in ponds, this correspondent recently visited the Bangladesh Fisheries Research Institute (BFRI) in Chandpur.
At BFRI’s laboratory
Although the projects had ended, the researchers were found to be busy researching ilish farming.
Hundreds of glass and plastic specimen jars were seen lined up on the tables of the lab in which ilish of different varieties, sizes, and ages had been preserved for some time through use of formalin.
Mohammad Ashraful Alam, senior scientific officer of BFRI Riverine Station in Chandpur, was testing ilish spawn with the help of a microscope to learn whether or not the fish was qualified to breed.
Pointing to a glass jar in which four ilish were preserved, Dr Anisur Rahman, chief scientific officer of the establishment, said: “These are the samples of ilish grown in ponds. They were preserved here during the second project period of fiscal year 2010-2011.”
Spawn, young and adult ilish caught from rivers and the sea, and ilish fry of different sizes of Meghna and Padma rivers had been preserved here since 1988, he added.
Although the researchers could not attain commercial success, they were able to grow ilish from ilish fry in ponds, which weighed up to 300 grams in a year during their research.
According to BFRI, the first initiative for ilish farming took place in 1988 in two ponds in Chandpur. Costing Tk6-7 lakh, the project ended unsuccessfully in 1995.
In 2004-2005, researchers tried commercial ilish farming for the second time and in 2010-2011 and 2012-2013 for the third time but failed again. About Tk4.6 crore was spent on the third project.
Funded by the United States Agency for International Development (USAID), research was resumed in 2015-2016 under the World Fish Organization’s EcoFish project, but that too did not see the light of success.
Why can’t ilish be farmed commercially?
Ilish or Tenualosa ilisha is an anadromous fish. These fish migrate from the sea to freshwater riverine environments to spawn.
They can swim up to 75 kilometres every day in the wide space of a river or a sea. Closed reservoirs or ponds are too congested for a group of ilish to move freely.
According to BFRI, it is very hard to maintain the necessary quality of food and water in closed water bodies like ponds because ilish do not eat supplementary food.
They eat natural foods, including different types of plankton that are found in rivers. Their diet also includes small plants, diatoms, rotifera, microcystis, oscillatoria, spirogyra, protozoa, alga, etc., said BFRI’s Ashraful Alam.
Ilish also adheres to a life cycle. Salinity, temperature and rainfall play a crucial role in this cycle.
They live and swim in directions opposite to the waves of the rivers and the sea and reach the Padma-Meghna for breeding. After the jatka phase, they go to the sea and then return to the rivers during breeding season as they prefer freshwater.
In the young (pre-adult) stage, they need estuarine and coastal water; high salinity marine water is required for them to be matured, which ponds are unable to provide.
A BFRI report said an ilish that is under 25 centimetres in size is considered a jatka, which fishermen are not allowed to catch. Male ilish appear to attain maturity at a size range of 26–29 cm, compared to 31–33 cm in case of females. But in the ponds, an ilish fry grows less than 25 cm.
During 2010-2013, 2,200 ilish fry — 8-12 cm in size — were collected from the rivers and the sea and released in three ponds. A year after being released, the ilish grew to weigh only 300 grams, whereas they would have weighed around 500 grams if they had spent that one year in their natural habitat.
Furthermore, the eggs of the ilish were found to be underdeveloped. Researchers said it was impossible to breed ilish with such eggs.
“We have to find out which protein can help ilish survive in ponds; this requires further research,” said Ashraful Alam.
Protecting rivers and natural resources
Experts have urged the authorities to take necessary steps to save the rivers of the country as ilish cannot be farmed commercially.
Besides, some half a million fishermen and 2.5 million people are directly or indirectly involved in ilish fishing and other related activities as a means of their livelihood.
The best way is to let ilish grow naturally in the rivers, said BFRI’s Dr Anisur.
Dr Md Niamul Naser, professor at Dhaka University’s Department of Zoology, said the government should provide alternative employment and ensure enough Vulnerable Group Feeding (VGF) during the ban on catching ilish to support fishermen and ensure that the fish grow naturally.
Sanctuaries need to be protected, pollution in rivers needs to be reduced, dredging needs to be done, and legal action has to be taken against the use of prohibited nets, he added.