AQUACULTURE DEPENDENCY ON THE WILD SEED
Pangasiid catfishes
Cambodia
In Cambodia records show that aquaculture of snakeheads and Pangasiid catfishes in cages and pens developed in the tenth century when wild fish captured in the peak fishery season were held over until later in the year when fish were less abundant and prices were higher. Fish species like “trey riel” (Cirrhinus siamensis), mixed with rice bran were/are the main feed ingredients used to fatten snakeheads and Pangasiid catfishes. Over time aquaculture of both snakehead and Pangasiid catfishes developed and intensified with deliberate capture of juveniles of both species for culture.
Today over 80 percent of aquaculture production in Cambodia comes from cages and pens in the Great Lake and Tonle Sap, and along the Mekong and Bassac rivers. River catfish Pangasianodon hypophthalmus is the main fish species cultured in earthen ponds, while snakehead Channa micropeltes is the main cultured species in floating cages. Intensive Pangasianodon hypophthalmus culture, is also conducted around Phnom Penh and in Kandal province because of its close vicinity to the urban markets of Phnom Penh (Phillips, 2002).
In 2004, 26 percent of the total number of fish seed used for aquaculture in Cambodia was wild caught. Of these, Channa micropeltes accounted for almost 78 percent (15 million fingerlings), Pangasianodon hypophthalmus for 4.7 percent (1 million) and Pangasius bocourti for 2.3 percent (600 000). Approximately 56 percent of aquaculture seed was imported (mainly from Viet Nam), while domestic hatcheries supplied only 18 percent (So and Haing, 2006).
There are a total of 14 government hatcheries in Cambodia, though not all function well because of poor water supply systems, limited staff capacity, funding and broodstock resources (So and Haing, 2006). The 5 largest freshwater fish seed hatcheries in Cambodia are the 4 government hatcheries (Bati Fish Seed Production and Research Centre in Prey Veng province, the Chrang Chamres Fisheries Research Station, the Toul Krasang Fish Seed Production Station in Kandal province, and the Chak Ang Rae Fish Seed Production Station in Phnom Penh) and the NGO SAO
Scale hatchery in Kandal Province, near Phnom Penh.
Viet Nam
Pangasianodon hypophthalmus (“tra” in Vietnamese) and Pangasius bocourti (“basa” in Vietnamese) have been traditionally cultured for centuries in Viet Nam (Peignen 1993, cited by Cacot, 1999; Lazard and Cacot, 1997). Today river catfish and Pangasius bocourti are the two main cultured freshwater fish species in Viet Nam in terms of both quantity and export value. Like Cambodia, the Vietnamese Pangasiid aquaculture industry developed from holding fish over to sell later when supply was lower and prices were higher. Culture of Pangasiid catfishes prior to 1980 was totally dependant on stocking of wild caught seed.
Pangasianodon hypophthalmus were first artificially propagated in Thailand in 1959, and the technology has since spread throughout southeast Asia (Trong, Hao and Griffiths, 2002). The doctoral thesis (in Vietnamese) “Induced spawning of the
Table 2
Pangasiid larvae and fry/fingerling production (millions) by province in the Mekong Delta region of Viet Nam, 2000–2005
Source: Provincial DOFI and DARD annual progress reports.
river catfish Pangasius hypophthalmus in the Mekong Delta” (Khanh, 1996) details the development, beginning in 1978, of artificial propagation techniques for the river catfish (Pangasianodon hypophthalmus) in Viet Nam. Prior to 1996, there was no hatchery production of Pangasiid catfishes in Viet Nam.
Table 2 shows the rapid rise in the hatchery production of river catfish seed in the Mekong Delta of Viet Nam, with larvae and fry/fingerling production increasing 11 and nearly 57 fold respectively, between 2000 and 2005.
In 2006 the 130 hatcheries (An Giang 15; Can Tho 5; Tien Giang 4; Vinh Long 3; and Dong Thap 103) in the Mekong Delta region of Viet Nam produced 10 billion river catfish larvae and the production of Pangasianodon hypophthalmus fingerlings reached 1 billion (Table 3).
Today there are a myriad of small-scale hatcheries and nurseries (<1 ha in area) supplying Pangasiid seed in Viet Nam and the price of larvae is down to as low as VND 2–3 each. Vietnamese hatcheries and nurseries produce more than sufficient for local demand, with excess river catfish larvae and fingerlings being exported to Cambodia (Edwards, Tuan and Allen, 2004). However Government Decree 15/2006/QD-BTS will prohibit the export of live Pangasiid larvae and fingerlings from September 2007 onwards.
In stark contrast, Cambodian hatcheries only produced a total of 883 840 river catfish fingerlings in 2004 (So and Haing, 2006).
The first “basa” (Pangasius bocourti) hatchery in the Mekong Delta of Viet Nam began operation in 1996. Ten hatcheries (2 in An Giang; 2 in Tien Giang and 6 in Dong Thap provinces) produced an estimated 15–20 million Pangasius bocourti larvae in 2006, selling at VND 100 (approximately US$0.006) each. Pangasius bocourti broodstock, which are held in cages, typically at stocking densities of 1.5–3 kg/m3, mature between February and June. Pangasius bocourti larvae are first fed on Artemia nauplii and later commercial pellets. Survival of Pangasius bocourti larvae
nursed to fingerlings at 90 days is approximately 70 percent. While the majority of Pangasius bocourti seed stocked
in Vietnamese grow-out systems is from hatcheries, a small proportion is still wild-caught. Private and government hatcheries produced an estimated 15 billion river catfish and 3 billion Pangasius bocourti seed in 2004 (MOFI, 2005).
Table 3
River catfish larvae and fingerling production, 2004–2006
Source: Annual 2006 progress reports from the Provincial Extension Centres of An Giang, Dong Thap, Tien Giang, Vinh Long, and Can Tho provinces.
Box 1
From wild seed fisher to hatchery owner
Hong My Hatchery, Hong Ngu district, Dong Thap
Mr My began catching and trading wild Pangasiid seed (Pangasianodon hypophthalmus, Pangasius bocourti and Pangasius krempfi) 38 years ago. Following training on spawning from the provincial Department of Agriculture and Rural Development (DARD) in the 1990s, Mr My established his Pangasiid hatchery in Hong Ngu district, Dong Thap province, close to the border with Cambodia.
Today the hatchery holds 25 tonnes of “tra” (Pangasianodon hypophthalmus) of about 6 kg each, 6.5 tonnes of “basa” (Pangasius bocourti) of about 8 kg each and 1.5 tonnes of Pangasius conchophilus of about 1.8 kg each, all of which were obtained from wild stocks. Most of the broodstock are held in floating cages on the nearby river. The broodstock are used for 5–6 years before being replaced.
Mr My has a total of 6 ha of ponds, 3.5 ha of which he owns and the remainder are leased. Hong My hatchery sells 90 percent of its production as 1-day old larvae, while 10 percent is sold as fingerlings after 45 days of pond nursing. The hatchery is run by 5 family members and 15 hired labourers. The hatchery’s main operating costs are feed for broodstock and spawning chemicals. Its main constraints were reported to be disease occurrence and the low fecundity of “basa” (Pangasius bocourti). Hong My hatchery sells mainly to Vietnamese nursery farmers and also to Cambodian wholesalers.
Culture systems for “tra” (Pangasianodon hypophthalmus) and “basa” (Pangasius bocourti) catfish in Viet Nam
River catfish is the major freshwater finfish produced in the Mekong Delta region of Viet Nam (Phillips, 2002) because it is hardier, grows faster, is less expensive to produce and has a fecundity up to ten times higher than Pangasius bocourti (Edwards, Tuan and Allen, 2004). In addition river catfish also has a higher dress out weight than Pangasius bocourti, with 3.1 and 3.7–3.8 kg fish, respectively, required to produce 1 kilogram of fillet (Edwards, Tuan and Allen, 2004). While tra is the major exported freshwater fin
fish from Viet Nam, Pangasius bocourti is still preferred for local consumption and sells for one third more than river catfish.
Pangasius bocourti are cultured almost exclusively in cages on tributaries of the Mekong River. From 1995 to 1999 there were approximately 3 000 Pangasius bocourti cages in the Mekong Delta of Viet Nam, producing 30 000 tonnes annually, most of which was destined for the domestic market (Nguyen Tuan, 2000). With increasing focus by producers on river catfish for export, there has been a significant recent decline in Pangasius bocourti production, with 800 cages producing an estimated 12 000 tonnes in 2006.
In Viet Nam, river catfish (Pangasianodon hypophthalmus) are cultured in monoculture in cages and net pens along the edges of rivers, intensively in ponds and in polyculture systems in small-scale ponds (Hung et al., 2003). An Giang and Dong Thap provinces have the greatest number of Pangasiid cages. Cage sizes in the Mekong Delta range from 50 to 1 600 m3, with larger cages commonly including living quarters on top and the submerged cage portion below (Phillips, 2002). Intensive pond culture of river catfish (Pangasianodon hypophthalmus) is concentrated in Can Tho, An Giang, Dong Thap, and Vinh Long provinces. Despite the higher risks (caused by high stocking densities and poor water flow) of characteristics unfavourable to export markets (e.g. yellow flesh), 50 percent of total Pangasiid culture is from ponds (Cacot, 2004). Small scale pond culture of river catfish including in VAC systems (Vietnamese acronym for garden, pond, and livestock quarters) is also found throughout the Mekong Delta (Edwards, Tuan and Allen, 2004). Recently river catfish and Pangasius bocourti have also been ‘exported’ to the northern and central regions of Viet Nam, and pilot culture has been conducted (Khanh 2004, cited in Hao, Hung and Tr?ng, 2005). However to date, the majority of Pangasiid culture in Viet Nam is from the Mekong Delta.
River catfish can tolerate dissolved oxygen as low as 0.05–0.10 mg l-1 (Browman and Kramer, 1985, cited by Cacot, 1999; Khanh, 1996), highly polluted water (chemical oxygen demand = 25), and being obligate air breathers, can be stocked at densities as high as 120 fish m-2. River catfish reach 1–1.5 kg after 8 months of culture and being omnivorous adapt to different kinds of feed (Khanh, 1996). The feed conversion ratio of river catfish is typically 1.9–2.0 on commercial pellets.
Ponds are usually stocked at 60–80 fish m-2, though some grow-out farmers may stock as high as 120 fish m-2. Grow-out cages are typically stocked at 100–150 fish m-3. Yields reach 300–400 and exceptionally 500 tonnes ha-1 crop-1 in ponds, and 100–120 kilograms m-3 crop-1 in cages. Yields as high as 500 tonnes ha-1 crop-1 have been reported from pen systems. Grow-out producers, have traditionally used home-made feed, but are increasingly moving to commercial pelleted feeds, which today supply an estimated 80 percent of feed inputs. Producers are aerating ponds and regularly exchanging pond water to reduce muddy off flavours and to produce whiter fleshed fish.
With increased culture area and intensity of Pangasiid production disease outbreaks like Bacillary Necrosis of Pangasius (BNP) are becoming more frequent. Outbreaks typically occur at the start of the rainy season (April–May) and the end of the flood season (October–November) (Crumlish and Dung, 2006). Although banned by the Ministry of Agriculture and Rural Development (MARD), many producers still treat diseases with antibiotics, plus disinfection agents. This has resulted in rejection of export shipments in Japan, the European Union and the United States of America. This is a priority issue for the government and the industry.
Production costs for pond and cage reared river catfish are relatively stable at approximately VND 7 000 kg-1 (US$0.43) and VND 9 000 kg-1 (US$0.56),respectively. River catfish and Pangasius bocourti products are exported to Europe (approximately 60 percent), Asian countries, Mexico, Australia (30 percent), the United States of America (<10 percent), and the Middle East. New markets like Russia are emerging.
In 2004 Pangasiid production reached 300 000 tonnes (MOFI, 2004). In 2005, a pond culture area of 4 912 hectares and 340 800 m3 of cages produced 416 908 tonnes of Pangasiid catfishes, with a total value of US$2 393 million. Of this, pond culture of river catfish, cage culture of river catfish and cage culture of Pangasius bocourti were 89 percent, 10.5 percent and 0.5 percent respectively. Mean productivity of river catfish in ponds in 2005 was 75.6 tonnes hectare-1 year-1, while mean productivity of river catfish and Pangasius bocourti in cages was 140 and 67 kilogram m-3 year-1, respectively (Southern Sub-Institute for Fisheries Planning, 2006). Estimated production of Pangasiid catfishes in 2006 was 842 000 metric tonnes, comprising 830 000 and 12 000 tonnes of river catfish and Pangasius bocourti, respectively. Viet Nam exported 286 600 tonnes of Pangasiid catfishes, valued at US$736 million in 2006 (Source: Viet Nam General Department of Customs). Viet Nam’s 2010 target production of river catfish and Pangasius bocourti is 1 million tonnes, with exports valued at US$800 million1 (Hao, Hung and Trong, 2005).
Culture systems for snakehead
Wild-seed based snakehead culture has been and still is practiced throughout the lower Mekong Basin, but is particularly important in Cambodia and Viet Nam. Until the early 1990s, an estimated 15–20 million wild snakehead seed weighing 0.3–0.5 g were collected annually between March and May, using lift scoop nets in the Mekong Delta area of Viet Nam. From 1999 onwards hatchery produced snakehead
1 Viet Nam surpassed 1 millon tonnes of Pangasiid production in 2007.
met Viet Nam’s demand for seed for stocking in grow-out systems. Today there are over 200 snakehead hatcheries in Viet Nam, with most located in Hong Ngu and Tam Nong districts of Dong Thap province. Broodstock are fed predominantly trash fish, and are held in small ponds, typically 200–500 m2 in area. When broodstock reach maturity, farmers make net spawning enclosures in which the snakehead naturally lay and fertilize their eggs. Presently hatcheries in the Mekong Delta area of Viet Nam produce about 20 million snakehead larvae annually.
Larvae are typically nursed in a blue nylon hapa measuring 3 x 4 x 1.5 m, holding 500 larvae, and fed on trash fish and/or fishmeal and fine rice bran, with 20–30 percent survival. Annual production of snakehead fingerlings, from hatcheries and wild collection, is estimated to be 15–18 million.
In the Mekong delta in Viet Nam, giant snakehead (Channa micropeltes) are cultured in cages together with Pangasiid species. It is estimated that they contribute 5 percent of the total output from cages (Trong, Hao and Griffiths, 2002). The Research Institute for Aquaculture No. 2 (RIA 2), in the south of Viet Nam has been spawning giant snakehead at Cai Be in Tien Giang province for several years and their staff have been disseminating spawning, nursing and grow-out technologies throughout the country (Khanh, personal communication). However since monoculture of snakehead is dependent on locally available cheap trash fish, which is in short supply, it is unlikely that giant snakehead culture will be anything other than a small-scale activity throughout Viet Nam for the foreseeable future.
In 1998, 954 farmers cultured snakehead in ponds and cages in Dong Thap province. Stocking at 25–50 fingerlings m-2, feeding low value freshwater trash fish, yields were 70–120 tonnes hectare-1 year-1 and total production was 4 641 tonnes. With the easy availability of hatchery produced snakehead seed, snakehead culture has expanded rapidly. Today stocking densities are typically 30–40 fish m-2, and yields 100–150 tonnes hectare-1 year-1 of market sized, 500–700 gram fish.
Cage culture of snakehead is popular in An Giang province, where yields range from 42.5–116 kg/m3. In 2003, An Giang province produced 5 294 tonnes of giant snakehead (Channa micropeltes).
In 2006 total production of snakehead (Channa micropeltes and Channa striata) in Viet Nam was an estimated 25 000–32 000 tonnes (Phuong, personal communication). In Cambodia, cage culture of snakehead (Channa micropeltes and Channa striata) has been practiced for over a century (Chevey and Le Poulain, 1940), but recently increased dramatically because they are high-value fish that can be marketed alive. Furthermore, they can be fed low value freshwater fish that are seasonally abundant in the country, thereby providing an efficient way of attenuating the seasonal peak fish harvest (Khay and Hortle, 2005). Cambodian snakehead culture (both cage and pen culture) is thus in a transition between capture and culture fisheries. The following examples illustrate this transition (Phillips, 2002):
• farmers who use the cages solely for transporting captured fish;
• farmers who hold and fatten fish for a few months, subsequently marketing them when price and demand are higher than at the time of capture; and
• farmers who stock wild-captured juveniles into cages and/or pens for feeding and grow-out to market size.
In 2004, there were 4 492 cages in Cambodia on the Tonle Sap Great Lake, and the Tonle Sap, the Mekong and Bassac Rivers (So and Haing, 2006), all of which at the time were entirely dependant on wild fish as seed, and feed (So et al., 2005). An estimated 20 million wild seed were collected for cage culture in 2004 (So et al., 2005), including 15.4 million giant snakehead seed, 1.1 million river catfish, 0.94 million Pangasius conchophilus and 0.62 million Pangasius bocourti. So et al. (2005) also estimate that 6.6 million wild river catfish fingerlings were stocked in ponds in Cambodia in 2004.
Capture-based aquaculture of Pangasiid catfishes and snakeheads in the Mekong River Basin 83
While Cambodia exported billions of river catfish fingerlings and tens of millions of Pangasius bocourti fingerlings in the 1980s, the trend reversed with the development of Pangasiid hatcheries in the Mekong Delta region of Viet Nam, with Cambodia importing 60 million fish fingerlings for cage and pond aquaculture in 2004, including 1.5 million river catfish. Viet Nam and thereafter Thailand became the major suppliers of seed to Cambodia.
While total hatchery production of fish seed in Cambodia expanded 33 fold from 560 000 in 1987 to 18.5 million in 2004 (So and Haing, 2006), Cambodian hatcheries supplied only 18 percent of the country’s total aquaculture seed requirement in 2004.
Cage culture of snakehead was banned in Cambodia in 2005, because of its reliance on small wild fish as feed. This resulted in a partial shift to cage culture of hybrid catfish (Clarias gariepinus x Clarias batrachus) in Cambodia.
In Lao People’s Democratic Republic, cage culture of snakehead based on wild captured seed is commonly practiced in the Nam Ngum Reservoir. Seed appear to be a limiting factor as prices have been increasing (Hambrey, 2002). There may therefore be an opportunity for Viet Nam to export giant snakehead seed to Lao People’s Democratic Republic.