Mekong River Commission

Why raise native fishes if it’s easier to
farm alien species already introduced?

Riverside restaurants in the Lao capital often hawk their barbecued fish as "Mekong fish" to unsuspecting tourists. What they're usually offering is a farmed African species introduced into the region from Japan to Thailand more than 40 years ago. This same species is increasingly seen in Cambodia and is now being stocked in Vietnamese ponds in the Mekong Delta that used to raise native catfish. Can real Mekong fishes really compete with these alien species?

Introductions of alien fish species into the countries of the Lower Mekong Basin date back to the late 17th century. According to the United Nations Food and Agricultural Organisation (FAO), the common goldfish (Carassius auratus) was introduced from China to Thailand between 1692 and 1697. Three centuries later, it was among at least 12 alien species established in the wild in Thailand. Although its date of introduction is not known, the same goldfish species has also been introduced from China to Viet Nam where it is now among at least 10 alien species established in the wild. In 2003, a study by British biologist Robin Welcomme and his Thai colleague Chavalit Vidthayonom identified 17 alien species that had either formed established populations in the Mekong Basin or had a strong possibility of doing so (see MRC Technical Paper No 9). Among them was the common carp (Cyprinus carpio). It was introduced from China to Thailand in 1913 and from Hungary to Viet Nam between 1969 and 1975 (the common carp is believed to be not one species but two groups from Asia and Europe). The study by Welcomme and Chavalit noted "considerable movement" of the common carp from Thailand and China to Lao fish farms and reservoirs. Of the major alien species introduced into the basin, they also found that at least three have been introduced into all four countries.

Out of Africa
The African catfish (Clarias gariepinus) was originally introduced from the Central African Republic to Viet Nam for aquaculture in 1974. It then spread internally throughout the countries of the basin, initially from Viet Nam to Cambodia and Lao PDR in the early 1980s and then from Lao PDR to Thailand towards the end of the decade. Male African catfish have since formed hybrids with females from an indigenous species from the same genus, the big head walking catfish (Clarias macrocephalus). While the alien species is not as commercially popular as the various native species of walking catfish, Welcomme and Chavalit found that the hybrid was "preferred" by farmers for its better growth rates and eating quality. The Nile tilapia (Oreochromis niloticus), also native to Africa, arrived in the region in 1965 when it was introduced from Japan to Thailand. Between the early 1970s and early 1990s, it was then introduced from Taiwan, the Philippines and Thailand to Viet Nam. It’s not clear when the species was introduced into Lao PDR and Cambodia. The red throat tilapia (Oreochromis mossambicus), also known as Mozambique tilapia, arrived in the region much earlier. It was first introduced from Malaysia to Thailand in 1949. It was then introduced from Africa and the Philipines to Viet Nam between 1951 and 1955, the same year it was introduced from Thailand to Lao PDR. The year of its introduction into Cambodia is not clear. According to Welcomme and Chavalit, the red-throat tilapia is not as highly-appreciated for its eating qualities as the Nile tilapia. Moreover, its former popularity has "waned" in favour of the more recently-now widely disseminated as fry from hatcheries and is "part of established commercial practice in support of stocking and aquaculture." The authors of the study also noted that the Thai government hatchery at Khon Kaen was rearing and distributing the GIFT strain of tilapia developed by the WorldFish Center and that several private hatcheries were licensed to produce and sell the fish for both cage and pond culture.

 

Table 1: Ten farmed alien species introduced into the Mekong Basin

Species	Route of introduction	Year
Mrigal carp (Cirrhinus cirrhosus)	India Lao PDR	1977
	India Thailand	1979
	Lao PDR Viet Nam	1984
African catfish (Clarias gariepinus)	Central African Repubic Viet Nam	1974
	Viet Nam Lao PDR	1980
	Viet Nam Cambodia	1982
	Lao PDR Thailand	1987
Grass carp (Ctenopharyngodon idella)	China, Hong Kong Thailand	1932
	China Viet Nam	1958
Common carp (Cyprinus carpio)	China, Japan, Israel, Germany Thailand	1913 +
	Hungary Viet Nam	1969-75
	Thailand, India Lao PDR	1977
Catla (Gilbelion catla)	India Lao PDR	1977
	India Thailand	1979
	Lao PDR Viet Nam	1984
Silver carp (Hypophthalmicthys molitrix)	China Thailand	1913
	China Viet Nam	1958
Bighead carp (Hypophthalmicthys nobilis)	China Thailand	1932
	China Viet Nam	1958
Rohu (Labeo rohita)	India Thailand	1968
	Thailand, India Lao PDR	1977
	Lao PDR Viet Nam	1982-84
Nile tilapia (Oreochromis niloticus)	Japan Thailand	1965
	Taiwan, Philippines, Thailand Vietnam	1973-74
	? Cambodia	?
	? Lao PDR	?
Pacu (Colossoma macropomum) *	? Thailand	?

*Pacu is native to the Amazon and Orinoco Basins in South America. In 2003, it was listed as introduced into adjacent waters (the Chao Praya Basin in Thailand). It has since been found in the Mekong Basin. According to Fishbase, the species was introduced into Thailand from Hong Kong and Singapore. It is considered a threat to humans as it has strong teeth that can chew hard nuts.

Source: MRC

Dr Cacot's scorecard Potential for Sutchi river catfish
Reproduction	5/5
Growth	4/5
Hardiness	4/5
Feeding	3/5
Market value	2/5

Strong demand for indigenous species
With their characteristics not well known and with limited supplies of fingerlings, how can indigenous Mekong fishes compete with such alien species whose characteristics are well known and which have better supplies of fingerlings for local farmers? According to Cambodian fish farmer Sieng Phan, one the most compelling reasons for raising indigenous species is that they tend to command higher prices as local people usually prefer them to alien species (see page 25). Lem Hai, another Cambodian fish farmer who also runs a family catering business near Phnom Penh, agreed. Even though he and two of his brothers farm one of the cheapest indigenous species-the Sutchi river catfish (Pangasianodon hypophthalmus)- he says prices compare favourably with tilapia, for example. "Tilapia can be more expensive but we get higher stocking densities with catfish," he said. "Also some people don't like tilapia which is usually just barbecued. Catfish is better for many Cambodian and Vietnamese dishes."But this is not just a matter of Cambodian or Vietnamese taste. Philippe Cacot of France's Agricultural Research Centre for International Development (CIRAD) surveyed Lao prices for 14 indigenous fishes and five alien species at Savannakhet market in 2005. He found that the average price of indigenous species was about $2.40/ kg-double the price of the alien species which averaged $1.20/ kg. Twelve of the indigenous fishes (various species of catfishes, carps and featherbacks as well as an eel and a snakehead) all fetched higher prices than the three most expensive alien species (common carp, tilapia and African catfish). And while the indigenous Sutchi river carp and small cyprinids were cheaper than these three alien species, they still fetched more than the other two alien species (silver carp from China and Mrigal carp from India) which were even cheaper.

 

Expanding native fingerling production
Dr Cacot has been working with the Living Aquatic Resources Research Center (LARReC) in Vientiane to address one of the biggest constraints of the indigenous aquaculture sector-the limited supply of fingerlings. His approach involves collecting breeders from the wild and either stocking them in ponds to develop new broodstock or transferring them to hatcheries to reproduce. After spawning, the breeders in the hatcheries are released back into the willd and the eggs produced are nursed in tanks or ponds. After 6 to 8 weeks, some of the fingerlings are released back into the wild while others are transferred to grow-out ponds or cages to be sold on the market. Speaking at the annual meeting of the MRC Fisheries Programme in Siem Reap in June, Dr Carcot asserted that the benefits of the approach were twofold. By diversifying production and improving hatchery and nursery techniques, it was contributing to aquaculture development in the basin. And by reducing the use of alien species and possibly protecting the wild breeders, the approach was also contributing to biodiversity conservation.

At the Lem Brothers pond near Phnom Penh, catfish farmer Lem Hon
(holding rope) works with Cambodian and Vietnamese labourers to set
an encircling seine net (uon hum) as they prepare to harvest fish for a
provincial wholesaler in May. The price of such nets can range from as little
as 200,000 riel ($50) to as much as almost 40 million riel ($10,000).
The nets are considered medium-sized fish gear and usually last about
three years.
Photo: Lem Chamnap

 

In Viet Nam, Sutchi river catfish is already a $1 billion export industry. But what about other Mekong species, apart from the nine already being promoted by the MRC Fisheries Programme? Dr Cacot identified krempf's catfish (Pangasius krempfi) as having "strong potential" for aquaculture in brackish water in the Mekong Delta, noting that the key location for this highly-migratory fruit-eating species was the Khone Falls area in southern Lao PDR. He estimated that about 55,000 breeders were caught every year around the falls as floodwaters rise in June and July. Another native fish with good potential for aquaculture, he says, is Jullien's carp (Probarbus jullieni), an endangered species that grows to 150 cm.

Table 2: Species farmed in the region

Native species	No	Alien species	No	Hybrids	No
Carps	8	Chinese carps	3	Shark catfishes	3
Shark catfishes	7	Indian carps	3	Walking catfishes	1
Other catfishes	6	Common carp	1
Climbing perches	5	Tilapia	1
Featherbacks	2	African catfish	1
Eels	2	Eels	1
Other prey fishes	2
Total	32		10		4
Annual production *	545,000		191,000		114,000

*FAO estimates in tonnes (2005). Production estimates for alien species and hybrids are believed to be conservative. Estimates for native species do not reflect the surge in annual Mekong Delta production of the Sutchi river catfish (Pangasianodon hypophthalmus) which recently exceeded 1 million tonnes. Production of the other dominant native species in regional aquaculture, the Java barb (Barbonymus gonionotus), is estimated at 100,000 tonnes a yaer.

Source: Philip Cacot, Agricultural Research Centre for International Development (CIRAD)

Dr Cacot addressing the annual
meeting of the MRC Fisheries
Programme in Siem Reap in June
Photo: Lem Chamnap

Faster growth but higher mortality
More than 300 individuals of this species are caught every year in December and January at a fishing ground next to Kho island, about 14 km upstream from Pakse in southern Lao PDR. Using a temporary hatchery on the island, the French biologist said that initial trials showed that "stripping" the spawning breeders for artificial propagation produced about 210,000 eggs of which about 150,000 actually hatched, resulting in 70,000 fingerlings after 6-8 weeks. The initial trial found that Jullien's carp grew much faster than the common carp during the first eight weeks after hatching. Growth rates were similar in the first few weeks, although the indigenous species was slightly larger at about 23mm after 25 days compared with about 20mm for the alien species. But the growth rates then started to diverge dramatically and after 60 days, the Jullien’s carp fingerlings were about 50mm compared with only 30mm for the common carp fingerlings. On the other hand, the alien species had a higher survival rate of 39% which compared with only 16% for the indigenous species. Could production of these fingerlings be an alternative or complementary form of income for fishermen around Kho island? Dr Cacot reckons fingerling production for this species could be even more profitable than the fish catch now if fishing restrictions are put into place. The local Jullien’s carp fishery currently involves about 55 boats from three villages. Assuming an annual catch of 400 fish weighing a total of 4.4 tonnes and a wholesale price of $3.50/kg, he estimates annual net income of about $12,400 from the existing fishery. At the same time, however, an estimated 42 million eggs are lost every year.

A model for the region
If fishing restrictions reduce the catch by 75% to only 100 fish a year weighing 1.1 tonnes, he forecasts that wholesale prices will double to about $7/kg. But that still won't be enough to compensate fishermen whose combined net incomes would then be $6,200, only half as much as they were before. The solution? A modest investment of $10,500 to build fifty 30m² canvas ponds. By stocking the ponds at a density of 250 fingerlings per square metre, Dr Cacot estimates that the additional eggs no longer lost as food could produce 375,000 fingerlings a year. If these fingerlings are sold to farmers at a rate of five cents each, estimated revenues would be $17,600 a year, generating net income of $7,100 once the investment costs are taken into account. Combined with the net income from the restricted fishing catch, total net income would be $13,300 a year, which is 7.3% more than what the fishery is earning now. Dr Cacot believes this model is sustainable for the whole region. So what next? "The use of the wild fish breeders seems to be a promising means of developing aquaculture while preserving the wild broodstock," Dr Cacot told the annual meeting in June. Moreoever, "there is an urgent need to protect fish reproduction." Mature breeders make up about 40% of the total catch in Champassak province in Lao PDR and the Cambodian provcinces of Stung Treng and Kratie. The combined catch is estimated at 2,000 tonnes every year, with many of the fish-and millions of eggs-ending up in fancy restaurants in Thailand. "Further research is necessary to fully control reproduction and nursing of the fish, checking the feasibility of production in various conditions, assessing the market for fingerlings, and assessing the effective potential for grow-out," Dr Cacot said "At the same time, regional exchanges are needed among the four MRC countries in areas such as information, study tours and training. The four countries could also exchange fishes in accordance with genetic considerations."But other steps are also needed by policymakers to promote indigenous species for commercial aquaculture. According to Dr Cacot, "public agencies should assist the private sector in providing fingerlings, broodstock and technical support." He also called for controlling the "footprint" of alien species by banning hybrids as well as the practice of using methyltestosterone to induce sex reversals in tilapia. Methyltestosterone is an anabolic steroid used to treat men with testerone deficiency and women with breast cancer as well as breast pain and swelling following pregnancy. It is also combined with estrogen to treat symptoms associated with menopause.

Vietnamese employees of a Cambodian fish wholesaler get ready to harvest several tonnes of catfish at the Lem Brothers fish farm on the outskirts of Phnom Penh in May. After setting the encircling seine net (uon hom) in the late afternoon, the fish were harvested shortly after midnight and transferred live by truck to markets in Kampong Cham, about three hours away by road.
Photo: Lem Chamnap

Further reading
Welcomme, R and Chavalit Vidthayanom (2003), The impacts of introductions and stocking of exotic species in the Mekong Basin and policies for their control, MRC Technical Paper No 10, Mekong River Commission, 38 pp