Bangladesh scientists breed the kakila artificially to save a native river fish

Scientists of the Bangladesh Fisheries Research Institute (BFRI) succeeded in August 2021 in breeding the kakila, a slender native river fish, artificially for the first time. The work was done at the institute's freshwater sub-station in Jashore after about three years of intensive research, and the first fry hatched from the eggs at four in the morning on 25 August 2021. BBC Bangla, which reported the breakthrough on 31 August 2021, said the kakila was the 31st open-water fish that the institute's scientists had bred artificially in their effort to save native species from extinction, and that the same work was making it possible to farm these nutritious fish in ponds.

The report set the kakila inside a wider story. Over the previous few decades a number of Bangladesh's small fish species had become endangered, yet the total production of small fish had risen significantly, and BBC Bangla put that rise down to the steady success of fisheries scientists' research. In the kakila's case, the chief scientific officer at the institute, Md Rabiul Awal Hossain, and scientist Md Shariful Islam described to the broadcaster how the fish was caught, moved, made used to a pond and finally brought to spawn.

According to BBC Bangla, 260 species of fish are found in the fresh waters of Bangladesh, and 143 of them are small fish. The report said fish smaller than nine centimetres are treated as small fish, known as small indigenous species or SIS. Fisheries researchers also use a wider size band: the 2015 Red List of Bangladesh's freshwater fishes speaks of medium-sized and smaller fish as those below 25 centimetres. The kakila is larger than either measure, with a common length of 30 centimetres in FishBase, but it shares the same open-water habitats and the same threats.

The International Union for Conservation of Nature (IUCN), the international body that works on nature conservation, had listed 64 of Bangladesh's fish species as threatened, the report said. Among them are the mahashol, the kharki, the pipla shol, the kala pabda and the bagh mach. For this reason, BBC Bangla reported, the government had drawn up a plan to protect several of these threatened fish by 2030.

Fisheries scientists had already rescued 30 fish from the danger of extinction through artificial breeding over the preceding few years, the report said. They include the shing, magur, puti, baim, tengra, foli, batasi, dhela, boirali, gutum and kholisha. With the kakila, the number reached 31.

The growth in output was large. According to statistics of the fisheries research institute cited by BBC Bangla, small fish production in Bangladesh had grown more than fourfold in a decade: from 67,000 metric tonnes in 2009 to about 250,000 metric tonnes in 2018. A year earlier, in September 2020, the fisheries and livestock ministry had given a similar series to The Business Standard: production of small native fish in ponds rose from 67,340 tonnes in 2009 to 2.41 lakh (241,000) tonnes in the 2017-18 fiscal year. The ministry said then that of the country's 260 species, 143 were small local fish.

The figure of 64 threatened species comes from the Red List of Bangladesh, Volume 5: Freshwater Fishes, which IUCN Bangladesh published in Dhaka in 2015. The assessment covered 253 species, of which 64, or 25.3 per cent, were found to be threatened: nine critically endangered, 30 endangered and 25 vulnerable. Another 27 species were near threatened, 122 were of least concern and the remaining 40 were data deficient. No fish was found to be extinct or regionally extinct. The previous assessment, made in 2000, had covered 266 species and found 54 threatened: 12 critically endangered, 28 endangered and 14 vulnerable.

All five fish that BBC Bangla named as examples sit in the most serious category of the 2015 list. The mahashol (Tor tor, the tor mahseer), the khorka or kharki (Schistura corica, a small loach), the pipla shol (Channa barca, the barca snakehead), the kala pabda (Ompok pabo, a catfish) and the baghair or bagh mach (Bagarius bagarius, a large river catfish) are all assessed as critically endangered in Bangladesh.

The Red List found that about 80 per cent of the threatened species belong to medium-sized and smaller fish groups, below 25 centimetres. It explained that small fish mostly live in small tributaries, floodplains and other small water bodies, many of which dry out in the dry season, and that they are badly affected by pesticides and by overfishing, including fishing by dewatering and the use of small-mesh nets. Most threatened fish were found in the north-west and north-east of the country, where habitat loss was most widespread.

The assessment listed the main threats. Rivers in Bangladesh carry about 2.4 billion tonnes of silt each year, which settles on river beds, floodplains and beel bottoms and leaves many water bodies too shallow or dry in the lean season. Wetlands are converted to farmland and settlements; embankments built for flood control and irrigation block the lateral movement of fish between rivers and floodplains; and roads built across floodplains with few fish passes fragment wetlands. Pesticides and fertilisers from crop fields reach the water, with pesticide use put at 13,000 tonnes, and untreated industrial and municipal waste pollutes rivers such as the Buriganga, Turag, Shitalakkha, Balu, Meghna, Karnaphuli, Surma and Dhaleswari.

BBC Bangla described the kakila's body as slender, long and almost cylindrical, with a long beak armed with sharp teeth in front of the mouth that makes it look rather like a crocodile. In some places it is also called kaikka or kakhle. The 2015 Red List gives its Bengali names as kankila, kaikya, kakila, kakhla and kaikka, and its English names as freshwater garfish, needle fish and silver needle fish. Its scientific name is Xenentodon cancila, first described by Hamilton in 1822, and it belongs to the needlefish family, Belonidae.

FishBase, the global fish database, records a maximum length of 40 centimetres and a common length of 30 centimetres. Its body is very elongated and slightly compressed, green-silvery on the back fading to whitish below, with a silvery band edged in dark running along the side and, in adults, a row of four or five blotches between the pectoral and anal fins. The fish lives mainly in rivers but also in ponds, canals, beels and flooded fields; it swims alone in mid-water, usually against the current, and can move in fast bursts when chasing prey. It feeds on small fish, crustaceans and insects.

The kakila is also found in Sri Lanka, India, Pakistan, Myanmar, Malaysia and Thailand, though its colour and size vary somewhat, BBC Bangla reported. The 2015 Red List adds Nepal and the Malay Peninsula to its range, and says that in Bangladesh it lives in rivers, haors, baors, beels, lakes, ponds and tidal brackish rivers and their tributaries all over the country.

Once, the kakila was plentiful in inland open waters such as rivers, haors, baors, canals and beels, and it reached the markets, so ordinary people could buy and eat it, BBC Bangla reported. But climate change and a range of human activities had put its habitat under threat. Pesticide use had damaged its breeding and feeding grounds, and the filling of water bodies had blocked its free movement. "This fish used to be found in plenty. But now it is hardly found anywhere except in some areas. In view of this the government took the initiative to protect this fish," Md Rabiul Awal Hossain told the broadcaster.

Its formal status was less severe than that picture suggests. The 2015 national Red List assessed the kakila as of least concern, calling it one of the commonest freshwater fish in the country; it noted that a recent survey indicated a slight decline in its population but that there were no concrete data to place it in a threatened category, and that its extent of occurrence of about 217,468 square kilometres and area of occupancy of about 11,857 square kilometres were above the thresholds for any threatened category. The global IUCN assessment, made on 12 August 2019, also lists the species as of least concern.

The research was carried out at the freshwater sub-station in Jashore, where the scientists worked intensively for about three years before achieving artificial breeding in August 2021, BBC Bangla reported. Jashore, a district of Khulna division covering 2,606.94 square kilometres, lies on the border with West Bengal, and its main rivers are the Bhairab, Chitra, Betna, Kobadak and Mukteshwari. The south-west is also the home of the baor, an oxbow lake left behind when a river changes its course, which Banglapedia describes as an important wetland that holds water throughout the year and supports a wide range of aquatic life.

The kakila had already been on the institute's research list a year earlier. In September 2020 The Business Standard reported that BFRI had produced the fry of 23 almost extinct native species and developed methods to farm them, and that research was then under way on the dhela, the shalbain, the kakila and the angus bhol.

The first step was to catch the kakila in open water and move it to a closed water body such as a pond, BBC Bangla reported. Great care had to be taken while catching and transporting the fish so that it was not harmed. "The kakila is an extremely sensitive fish. It was kept in water, given an artificial flow of oxygen in a water tank and brought very carefully by vehicle. Then it was released into pond water and conditioned," Md Rabiul Awal Hossain said.

He explained that the scientists first created a suitable environment in the pond, keeping in mind whether the fish likes a current and whether it likes to live among aquatic plants. The fish was then given one to two years to adapt to its new surroundings. During this time its behaviour and feeding habits were watched, and it was made used to the closed pond by feeding it live fry of carp produced in hatcheries and live small fish collected from open water bodies.

"After the net was dragged through the pond to catch it, the fish was released into the water again. At one time these fish used to die on top of the net. But at some point we saw that the fish had got used to it, that is, they had become accustomed to the new environment," Mr Hossain said. Only after that was breeding arranged.

In nature the kakila usually breeds in flowing water, especially in rivers and in areas flooded during the monsoon, BBC Bangla reported. Although adults live in places without floating aquatic plants, the female lays her eggs under the leaves of aquatic plants and on floating roots. The scientists found that the kakila's eggs are at their most mature in July and August, so they chose that period for breeding. FishBase likewise records that the species' eggs are attached to objects in the water by tendrils on the egg surface.

"We started breeding trials from April. First, research was done on its physical characteristics. When we saw that the fish was ready for breeding, different types of hormones were applied in different doses," Md Shariful Islam told BBC Bangla. After a number of trials the scientists found that at one particular dose the fish became excited; the female laid eggs and the male released sperm over them, fertilising them, and the scientists then took it that the dose was suitable for breeding. The report did not give the hormones or doses.

Four pairs of fish were then released into a cistern in which the scientists had created a shower-like flow of water. Because the kakila usually lays its eggs on aquatic plants such as water hyacinth, the same kind of setting was created inside the cistern. About 40 hours after the hormone injection the female released her eggs and the male then released his sperm. To keep the eggs from being spoiled by any contamination, or eaten by larger fish, they were kept in intensive care.

"The kakila's eggs are sticky. They stick firmly to the water hyacinth. We saw that neither the father nor the mother fish was eating these eggs. Rather, they were guarding the places where there were more eggs. We understood that their parental care is extremely strong," Mr Islam said. The observation differs from aquarium accounts summarised by FishBase, which record no parental care in the species, a sign of how little had been studied about the fish in the wild. Finally, at four in the morning on 25 August 2021, the fry came out of the eggs.

The scientists still did not have a complete understanding of the fish, BBC Bangla reported, because the kakila had never been researched before, so the institute's scientists were doing the work for the first time. Md Rabiul Awal Hossain said they were moving forward step by step with the knowledge gained from this research.

The Bangladesh Fisheries Research Institute is an autonomous research organisation set up in 1984 as the national institution for planning, coordinating and conducting fisheries research; it actually began to function in 1986, according to Banglapedia. Its aims include basic and adaptive research for the best use of all living aquatic resources, low-cost and environment-friendly fish culture and management technologies, and the training of skilled technical staff. A Director General heads the institute, and a Board of Governors chaired by the Minister of Fisheries and Livestock oversees it.

The headquarters is in Mymensingh. Banglapedia lists four research stations: the Freshwater Station in Mymensingh for freshwater aquaculture, the Riverine Station in Chandpur for river fisheries, the Brackishwater Station at Paikgacha in Khulna, and the Marine Fisheries and Technology Station in Cox's Bazar, along with sub-stations at Rangamati for reservoir fisheries and at Santahar for floodplain studies. The Freshwater Station covers about 40 hectares near the Bangladesh Agricultural University campus and has 118 drainable experimental ponds and a carp hatchery able to produce more than 300 million fry a year. The Business Standard listed the institute's branches in 2020 as Bogura, Santahar, Syedpur in Nilphamari and Jashore.

The institute had widened its work on native fish in the year before the kakila was bred. In September 2020 a gene bank for endangered native fish, described as the first of its kind in the country, was launched at the BFRI headquarters in Mymensingh, the Dhaka Tribune reported; the institute's Director General said at the launch that the country had 260 fish species and that 143 of them were then held in the gene bank. The same month the Director General told The Business Standard that the work had made gene preservation, breeding techniques and commercial farming of these fish possible, and that about 300 crore fry of local species were being supplied each year.

The kakila is tasty and rich in micronutrients, BBC Bangla reported: it contains various vitamins, protein, lipids and important minerals such as calcium, phosphorus, iron and iodine, and scientists said it carries more of these than other small fish. "These minerals are very beneficial for the health of ordinary people, especially children. They are extremely necessary for those suffering from anaemia and for raising the body's resistance," said Md Shariful Islam, the scientific officer at the institute.

Research published before 2021 explains why the loss of such fish matters for diets. A study in the journal PLOS ONE in April 2017 by researchers working with WorldFish analysed national household surveys from 1991, 2000 and 2010, covering 25,425 households. It found that fish consumption in Bangladesh rose by 30 per cent between 1991 and 2010, while consumption of non-farmed species fell by 33 per cent and was replaced by farmed fish. Despite eating more fish, people got significantly less iron and calcium from fish, because the common farmed species are generally of lower nutritional quality than the diverse species from capture fisheries.

The same study noted that the haem iron content of small indigenous species in Bangladesh had been measured as high as 93 per cent of their iron, against about 40 per cent in red meat. It recorded that Bangladesh's fish supply per person rose from 7.6 kilograms a year in 1990 to 19.2 kilograms in 2013, and that the share of aquaculture in that supply rose from 23 to 55 per cent. Its authors recommended pond polyculture of large fish together with small indigenous species, the stocking of nutrient-rich small fish in community-managed wetlands, and public investment in research on the artificial reproduction of key nutrient-rich small species, with the technology passed on to private hatcheries.

Fish is central to the Bangladeshi diet. The 2015 Red List, citing Department of Fisheries data for 2014, said fish provided 60 per cent of the animal protein in the diet and that intake was 52 grams per person per day against a recommended 68 grams. It said 1.2 million professional fishers depended on fishing full time, and another 10 million people fished for subsistence or to add to their income.

The concern for fish conservation in Bangladesh dates back to 1950, when the fish conservation law was promulgated; it was amended in 2012, the 2015 Red List recorded. The law restricts mesh sizes and bans destructive fishing gear and methods, with provision for punishment and fines. The country's Fisheries Policy of 2000 focuses mainly on inland open-water fisheries, and the Wildlife (Conservation and Security) Act 2012 includes several fish in its Schedule 2, with provision to restrict fishing for them.

The Red List authors also set out what they thought was still needed. Their recommendations included:

• a species action or recovery plan for all of Bangladesh's freshwater fish;
• amending the fish conservation law and the 2012 wildlife act so that they focus on threatened fish species;
• stopping further conversion of wetlands and building fish passes into flood-control projects, roads and highways;
• re-excavating degraded water bodies and reopening connecting channels;
• banning long-persistent pesticides and the discharge of untreated industrial and municipal waste into water;
• setting up more fish sanctuaries, especially in the north-west and north-central regions, and campaigning against dewatering and destructive gear.

Photo: Guérin Nicolas / Wikimedia Commons (CC BY-SA 3.0)

Sources: BBC Bangla, IUCN Bangladesh (Red List of Bangladesh, Volume 5: Freshwater Fishes, 2015), FishBase, Banglapedia, The Business Standard, Dhaka Tribune, PLOS ONE (Bogard et al., 2017)