PART IV. TONLE SAP AQUACULTURE

Description of Tonle Sap aquaculture systems
Environmental aspects
National policies, strategies, plans and programmes for Tonle Sap aquaculture development

Total aquaculture production in Cambodia for 1999 is officially reported at 15 000 tonnes. This is about 5 percent of the officially reported total fish production in the country and between 3.1 and 4.4 percent of the estimated total fisheries production for that year.

Data on aquaculture production need to be considered with caution since they are not obtained from sampling or from recorded data of aquaculture facilities. They are mostly collected through interviews with fish farmers and most are estimations of the yearly production by staff of the Department of Fisheries (Nann and Sensereivorth 2000). It is not possible to assess the extent to which these figures approach actual annual aquaculture production but if they follow the general trend of official data on fisheries production, the real figure is likely to be considerably higher. Data on aquaculture facilities are more reliable since these are collected by the Department of Fisheries as part of the licensing process that is required for most aquaculture activities. There is no specific legislation for aquaculture as such. For pond and pen operations of more than 0.5 ha or cages of over 15 square metres, a licence is required from the Department of Fisheries.

Table 3.1 Number and surface areas of ponds, cages and pens in operation in the provinces bordering the Tonle Sap ecosystem in 1999. Fish production data not differentiated by source of production (after Nann and Sensereivorth, 2000)

Province	Ponds		Cages		Pens		Fish production (tonne)
	Number	Area (m2)	Number	Area (m2)	Number	Area (m2)
Phnom Penh	112	516 000	308	14 916	-	-	1 430
Kandal[3]	590	409 460	960	7 620	-	-	2 400
Kampong Thom	600	60 000	380	12 700	-	-	1 800
Kampong Chhnang	22	2 090	520	4 680	-	-	2 200
Pursat	219	410 000	53	4 900	62	9 700	1 650
Battambang	170	54 129	41	57 897	-	-	1 250
Siem Reap	489	88 320	325	25 590	146	120 150	1 400
Total	2 202	1 539 999	2 587	128 303	208	129 850	12 130

The overall contribution of aquaculture to fish production in the country is marginal. However, aquaculture in Cambodia does contribute to food security by making fish available in areas with little or no natural fishing grounds. It provides animal protein and diet diversification and contributes to food availability. The importance of rural aquaculture lies mainly in food security at household level.

The contribution of aquaculture to food security for the communities bordering the Tonle Sap ecosystem is minimal. Trends in the capture fisheries catch of an increase in the proportion of smaller, lower-value species, have led to an increase in the part of the catch that is used as feed for cultured fish. Cultured fish may well be competing with poor people for small fish from capture fisheries for food (Mekong Secretariat, 1992).

Description of Tonle Sap aquaculture systems

There are three main aquaculture systems in Cambodia: cages, pens, or a combination of these, and ponds. A shown in Fig. 3.1, most of the production comes from cages and pens, with pond aquaculture only recently producing a considerable amount of fish.

In the Tonle Sap ecosystem, aquaculture is only practised in cages and pens. According to Csavas et al. (1994), 77 percent of all cages in Cambodia are situated in rivers (Tonle Sap channel, Bassac, Mekong) and only 23 percent in the Tonle Sap lake. The Tonle Sap aquaculture originated from the stocking of surplus fish catches during the peak fishing season. Aquaculture was very small until the 1960s, when it began to expand.

Figure 3.1 Freshwater aquaculture production in Cambodia, 1984-1999 (after Nam and Thuok, 1999). Data for 1999 (Department of Fisheries) not differentiated by source

Most species used in aquaculture in Cambodia are indigenous. Species recently introduced are less popular and fetch in general lower prices. All species used in cage or pen aquaculture are caught as fingerlings or juveniles from the wild.

Table 3.2 Aquaculture production in cages and pens in Cambodia. Production and value figures for 1998 (after Nam and Thuok, 1999 and Mekong Secretariat, 1992). w: wild, h: hatchery; L: local, E: export; C: common, R: rare

Species1	Production (Tonne)	Value		Origin of seed	Market	Frequency of culture
		kg-1 (US$)	Total (US$ 1000)
Pangasianodon hypophthalmus	5 332	0.80	4 266	w	L/E	C
Pangasius larnaudiei	144	1.25	180	w	L/E	C
Pangasius conchophilus	108	1.50	162	w
Pangasius pangasius	100	1.00	100	w	L/E	R
Pangasius micronema	72	0.90	65	w	L/E	C
Channa micropeltes	1 969	2.00	3 938	w	L	R
Channa striata	104	1.50	156	w	L/E	C
Cirrhinus microlepis	174	1.50	261	w	L/E	C
Clarias batrachus		1.50		h	L	R
Leptobarbus hoeveni				w	L	C
Chitala ornata				w	L/E	R
Oxyeleotris marmorata		8.00		w	L/E	R
Puntioplites proctozysron				w	L	R
Barbodes altus				w/h	L	C
Barbodes gonionotus				w/h	L	C

¹ Fish names adjusted from the original document to accord to Rainboth (1996).

Recent revisions of the Pangasiidae make it difficult to compare older data with recent ones.

The collection every year by the 651 illegal dai fisheries units on the Mekong of an estimated 150 million Pangasianodon hypophthalmus fry floating downstream is likely to have an impact on the recruitment of the stocks in the Tonle Sap. Most of these fish caught are exported to Viet Nam, although a small part is used for stocking of cages in Cambodia. The bycatch of an estimated 400-850 million fry of other, mainly cyprinid species, is discarded (Bun, 1999).

Most of the fish cultured in cages in Cambodia originate from the Tonle Sap. These are usually not fry or even fingerlings but larger juvenile fish. The total quantity of Pangasius pangasius juveniles from the Tonle Sap that is exported to Viet Nam for cage culture is estimated at 250 tonnes per year or about 2 million fish (Mekong Secretariat, 1992).

Table 3.3 Collection of seed from the wild in the Tonle Sap ecosystem

Fishing ground	Gear	Time	Species	Size	Use
Tonle Sap lake and channel	Fishing lots and traps	April-May, receding water	Pangasianodon hypophthalmus	100-125 g	Stocking in cages and pens
Tonle Sap lake and channel	Fishing lots and traps	April-May, receding water	Pangasius pangasius	100-125 g	Export to Viet Nam for cage culture
Mouths of small tributaries to the Tonle Sap channel		September-October, closed season (illegal)	Pangasianodon hypophthalmus	4-8 cm	Stocking in cages and pens
Tonle Sap channel	Dai	November-February	Pangasianodon hypophthalmus	50-100 g	Stocking in cages and pens; high mortalities as dai are not designed to catch fish alive
Mekong		September-October	Pangasius sp. (including Pangasianodon hypophthalmus)	small	Stocking in cages and pens
Tonle Sap lake and channel	Rod and line	September-October	Pangasius sp. (including Pangasianodon hypophthalmus)	80-150 g	Stocking in cages and pens
Tonle Sap lake and channel	Scoop net and small trap	August, flood season	Pangasianodon hypophthalmus	5-15 cm	Stocking in cages and pens
Floodplains	Scoop net and cast net	July-August	Channa micropeltes	3-10 cm, schooling	Stocking in cages and pens
Kampong chhnang			Oxyeleotris marmorata	100 g	cage culture

Cages are constructed from wood or bamboo with a wooden frame, often in the shape of a boat and in a wide variety of sizes. Cages are reported of 26 to 3 000 m³, with the larger cages being used for transport of marketable fish to Phnom Penh (Mekong Secretariat, 1992). The larger cages often have the house of the owner and occasionally a pigsty constructed over them. Cages for actual fish culture are usually smaller, 360-750 m³.

Initial stocking densities vary according to the species and the availability of seed. Stocking densities in cages of 10 kg/m³, and up to 15 kg/m³ at the beginning of the culture period, of Pangasianodon hypophthalmus of about 100 g are common. In pens, this is about 1.5-2 kg/m². The difference between pens and cages for holding of surplus catches and actual aquaculture operations is not always clear. In the former case, much higher stocking densities are often found for short periods.

· Grow out

The pangasid catfish are kept in cages for a period of eight to twelve months. In this time, the stocking density will increase to 60 or more kg/m³ depending on the availability of good quality feeds and on mortality. Mortality is reportedly high, at 10 percent of the initial load, but much higher (20-30 percent) in some cases (Demuynck, 1995). Especially during the dry season, outbreaks of disease occur, which can decimate weakened populations in the cages. When the fish have reached 1-1.5 kg, they are transported for marketing, usually to Phnom Penh.

The preferred feed for the caged pangasids is fresh chopped fish. Usually cheap, small species commonly referred to as “trash fish” or third-grade fish are used for this purpose. They include mainly small cyprinids, which are abundantly available from December to March (Mekong Secretariat, 1992). When fresh fish is not available or too expensive for use as feed, a variety of alternative feed stuff is used: dried trash fish, rice, rice bran, boiled maize, chopped aquatic plants, etc. Few reliable data on in situ food conversion for cage culture are available. Nuov and Nandeesha (1992) report a conversion rate of four for fresh trash fish during the fishing season.

In the flooded or floating villages of the Tonle Sap lake, a combined system of pens and cages is used for the culture of Pangasianodon hypophthalmus. During the dry season, the villages, which consist mostly of houses on stilts or of boats, are out in the lake near the dry-season shoreline. Juvenile catfish are kept in pens in the shallow water or in canals. During this time (February-July), small fish are abundantly available and used for feeding the fish in the pens. At the rising of the floodwaters, village constructions are relocated to elevated places more inland and the fish are transferred from the pens to cages that are moved together with the village. Fish that are of marketable size are sold in this period. Whilst in the cages, there are no substantial quantities of cheap fish available and the fish are fed a survival diet consisting of mainly aquatic weeds and rice bran. When the water levels recede again, remaining fish that have not been sold are transferred back into the pens after the village has returned to the dry-season shoreline.

The cage culture of the carnivorous snakehead (Channa) species differs from that of pangasid catfish. The fish that are collected from the wild are actual fingerlings, much smaller than the average size for the catfish (Mekong Secretariat 1992). In a first phase, these fingerlings will be cultured by nursery farmers for one or two years until they reach 250 g. Then, in a second phase, they are sold to grow-out farmers. The cages used for snakehead are usually smaller, less than 1 000 m³ (Nam and Thuok, 1999). The productivity of the fast-growing snakehead in cages is reported to be as high as 150 kg/m³ per year, starting from an initial stocking density of 10-40 kg/m³ (Nam and Thuok 1999). Snakeheads are not transported in cages but by live well boat.

Snakeheads are strictly carnivorous and will feed only on fresh fish. This presents a major constraint since the availability of cheap, fresh fish is very seasonal. In many cases, this has encouraged illegal fishing during the closed season, and in some places, licences for snakehead culture are no longer issued because of this. Feeding quantities and frequency seem to be entirely determined by the availability of fresh fish. This results in significant periods of starvation. Food conversion rates are reported to range from four to six (Mekong Secretariat, 1992).

· Constraints

Constraints to further aquaculture development in the Tonle Sap are mainly related to the husbandry systems as practised. To some extent, cage culture serves as a processing tool for the large and growing amounts of small fish that are seasonally available. So far, alternative processing has failed to develop and the high prices the cultured species fetch are an incentive to continue present aquaculture operations.

Paradoxically, feed is apart from the raison-d’être of the Tonle Sap aquaculture also the main constraint for its further development. Given the perceived trends in the composition of the capture fisheries (van Zalinge and Thuok, 1999), the share of small trash fish will continue to increase. It is not clear how the total volume of fish will evolve, but the seasonal availability of cheap fish suited for fish feed might well increase. At the same time, the pressure on this share of the capture fisheries for it to be used for human consumption or for livestock is certain to rise. Conversion rates at present are low for the cultured fish and the quantities of fish fed to the cultured species are substantial. Mekong Secretariat (1992) speculates that the total amount of trash fish used in aquaculture could be sufficient to satisfy the annual fish consumption of one million people. Although over-simplified and based on inaccurate estimations of food conversion and fish consumption, a considerable amount of the catch by capture fisheries is not directed at satisfying food requirements of the rural poor but at the inefficient production of high-value fish for the urban population.

Total dependence on seed caught from the wild makes the activity susceptible to annual fluctuations in seed availability. It does not allow much selection among the fish used for stocking.

Another constraint on the development of the Tonle Sap aquaculture is the little control the present system allows over water quality. The only management options available to the farmers now are stocking density and location of the cages. However, the high costs of the cages makes that the farmers want to maximize stocking density and keep the cages with the fish in safe places, usually crowded together in the floating or flooded villages, where water quality can become really poor and lead to massive mortality.

The high investments and the high price of credit prevent a further up-scaling and intensification of the cage and pen culture as practised in the Tonle Sap.

Environmental aspects

The present system of aquaculture in cages and pens does not have much impact on the environment. There is very little pollution, and effects of eutrophication or other impacts on the water quality outside the cages are probably insignificant. This is mostly because of the big changes in water quality that occur naturally and through other human activities in the same area.

On the other hand, there is a growing impact of the environment on aquaculture. Fluctuating water levels do not only determine the amount of seed and of trash fish available as feed, but also directly affect the position of the cages and the depth of water in which they can be kept. Siltation may hamper the movement of cages. Direct impacts on the cultured fish are probably limited since most of the species naturally occur in habitats with poor water quality: low dissolved oxygen levels, high turbidity, high temperatures, etc. Pollution in the floating or flooded villages is a risk for the aquaculture.

National policies, strategies, plans and programmes for Tonle Sap aquaculture development

Most ongoing efforts in aquaculture development in Cambodia are dealing with rural aquaculture in ponds in areas with no or limited access to productive fishing grounds.

Nam and Thuok (1999) present the outline of the aquaculture development plan in Cambodia for 2000-2020. The plan entails:

• developing regulations and laws relating to environmental assessment and management of aquaculture development;
• close assessment of resources for development;
• determining possible market demand for domestic consumption and export;
• taking into account the trend of fish consumption in relation to disposable income;
• identifying priority in the use of land and water resources and their allocation in relation to economic growth, and the conflict with other use;
• identifying improvement of technologies through research and experimentation on provincial/municipal, national, regional and inter-regional cooperation;
• strengthening aquaculture extension activities in the use and management of natural resources and technology applications to meet the requirements of local market demand and export;
• promoting sustainable aquaculture development and encourage aquaculture industry investment.

The objective of the National Aquaculture Development Plan is to envisage the state and problems of aquaculture development in Cambodia over the next twenty years. The plan is in line with the National Agricultural Development Plan 1999-2010.

The plan foresees little focus on the cage and pen culture in the Tonle Sap ecosystem. There are a number of more general issues that will impact on this, such as marketing improvement, development of extension services and capacity in the Department of Fisheries and the revision and update of relevant legislation. No concrete plans beyond “Introduction of improved cage/pen culture techniques” are presented. Most emphasis, both in the objectives as in the priority areas, lies on the further development and extension of rural aquaculture in areas that are “fish-deficient”.