MANAGEMENT, CONCLUSIONS, REFERENCES

MANAGEMENT

Often the capture of juvenile fishes is seen as a wasteful practice. Conventional wisdom tells us that juveniles should be left to grow to their full potential before being harvested. This conventional wisdom has also taken hold in the Mekong basin, where the capture of juvenile fishes for use in either culture or consumption has generally been banned.

In Cambodia, the bag net (dai) fisheries targeting Pangasiid larvae were banned in 1994. However, in spite of the ban, the number of bag net units in operation increased to 948 in 1998, up from 650 units in 1981 (Van Zalinge et at., 2002). Since then however, enforcement has been strengthened. The “New Fisheries Law” calls for the protection of aquatic biodiversity and the environment (So and Haing, 2006).
In Viet Nam, the “New Fisheries Law” came into force in 2003. This is a legislative framework within which specific directives will be developed to accommodate the legal aspects of specific fisheries issues, such as capture fisheries management, aquaculture and habitat/species conservation.
In relation to the capture of wild seed for aquaculture, the New Fisheries Law states that the exploitation of fish smaller than regulated size is prohibited, except for permitted aquaculture purposes.
The provincial authorities in Viet Nam have some legislative powers for specific management regulations of provincial level fisheries, including juvenile fisheries. In both An Giang and Dong Thap provinces, for instance, the use of dais to capture Pangasianodon hypophthalmus larvae was banned in 2000. The timing of this ban coincides well with the emergence of increased hatchery seed production that was subsequently able to meet the Pangasiid seed demand of the area.

Regulations for snakehead juvenile fisheries, include some size restrictions, e.g. in An Giang Province the capture of snakeheads below 10 cm in length is illegal. From 1 May to 1 June each year, fishing for juvenile snakeheads is completely banned to reduce fishing pressure during the peak spawning season of snakeheads (Sjorslev, 2001). However, enforcement of these regulations appears to be extremely weak.
Most existing legislation related to the capture of juveniles and their use in aquaculture, is generally based on weak and unreliable data.
With the massive recruitment occurring within the Mekong ecosystem, for at least three of the four species covered in this paper, and with the extreme seasonality of the fisheries, the capture of juveniles may actually be a sustainable resource exploitation approach. The key management issue for the sustainability of the capture-based aquaculture practice is whether the use of trash fish-based feeds is sustainable, and if not, whether these feed inputs can be replaced by other protein sources.
In the extremely complex and multi-species setting of the Mekong basin fisheries, it is important that all management issues are seen within the larger, ecosystem context. Experiences from past decades suggest that if essential habitats for the targeted species are protected and maintained (in terms of quality as well as quantity), juvenile fisheries can continue to be conducted in a sustainable manner.

CONCLUSIONS

• Aquaculture traditionally developed in the lower Mekong basin as an integrated element of capture fisheries to transfer a low value, seasonal surplus into high value fishes (such as Pangasiid catfishes and snakeheads) that could be marketed all year round.
• Wild seed is used in cage and pond culture (Pangasiid catfishes) and cage and pen culture (snakehead) throughout the basin, particularly in Cambodia and Viet Nam.
• Traditionally, these culture systems relied on wild-caught, low-value “trash fish” from the Mekong (e.g. the small cyprinid genus Cirrhinus) as feed. This is still the case in most places. Today marine trash fish are also being utilized as a feed input to accommodate the increasing demand in the Mekong Delta of Viet Nam. Trash fish, however, is increasingly being replaced by commercial pelleted feeds, particularly in Viet Nam.
• For Pangasiid catfishes, traditional capture-based aquaculture systems triggered the development of hatchery technology which today meets the demand for seed within Viet Nam and Thailand, with surplus seed exported to Cambodia and Lao People’s Democratic Republic.
• Snakehead culture continues as a capture-based aquaculture system in most parts of the basin, except in Thailand. The large recruitment from natural ecosystems and their relatively easy capture means that large-scale hatchery production of snakehead seed (particularly the giant snakehead, Channa micropeltes) is financially unattractive.
• Current data and information suggests no significant negative impacts of juvenile fisheries on wild populations of Pangasiid catfishes and snakeheads. Both species groups have maintained healthy and extremely productive wild populations in spite of juvenile fishing pressure.
• For the two main Pangasiid species, recent genetic studies indicate that the bottleneck for sustainable management of both species is the protection of their spawning habitats.
• When wild capture of aquaculture seed is increasingly replaced by hatchery-reared seed (as has happened with Pangasiid aquaculture in the Mekong delta of Viet Nam), it is important to introduce sound genetic management practices. These include using broodstock of local origin and/or periodically replacing broodstock with newly captured wild broodstock from local sources.
• The use of low-value/trash fish from within the Mekong basin as well as from marine sources poses the biggest challenge to the industry in terms of ecological and environmental sustainability.
• The socio-economic importance of past and present juvenile fisheries in the Mekong basin, and their subsequent banning in some areas, has not been adequately assessed.
Capture-based aquaculture of Pangasiid catfishes and snakeheads in the Mekong River Basin 89
• Capture-based aquaculture, including the practices of capturing juveniles and using wild-captured resources for feed, should be assessed and managed within a larger-scale ecosystem approach.

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