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|WILD HARVEST FISHERY<to be added>||AQUACULTURE.
Risk of escaped fish to wild stocks
No data are available on the frequency of escapes, but the impacts of escapes are probably minimal since basa is native to the region (Ish and Doctor, 2007). However, scientists are concerned about possible hybridization between basa and tra (Pangasius hypophthalmus) (Ish and Doctor, 2007).
Risks of disease and parasite transfer to wild stocks
No evidence for transmission of disease from farmed stocks to wild stocks or vice versa (Ish and Doctor, 2007).
Fishing for fry was banned in Cambodia in 1994 (Bun 1999) and in Vietnam in 2000 (van Zalinge et al., 2002). Illegal fishing for fry still occurs but to an unknown extent. Hatchery-produced fry and the more frequent enforcement of the regulations is expected to have reduced the capture of wild fry (van Zalinge et al., 2002).
Location of cages and effluent effects
In the Mekong River Delta, siting of cages has had a minimal effect on the environment (Ish and Doctor, 2007). The quantity of organic matter in effluents depends on the type of feeds; home-made feeds can lead to increased water pollution (Edwards, 2004). The environment here is already highly degraded from non-aquaculture sources, and the area is heavily used by a large human population.
Use of trash fish and fishmeal
Farmers own feeds are made from mixing rice, vegetables and trash fish; manufactured feeds normally use imported fishmeal mixed with ingredients such as corn meal and soybean meal. Food for basa does not cause environmental problems (Tung et al., 2004). Farmers often introduce scavenging fish which feed on excess feed to help reduce waste.
Waste disposal from processing factories
Factories not equipped with waste treatment facilities except for some oxidation and sedimentation ponds that are unable to fully treat processing waste properly (Thung et al., 2004).
Impacts of environment on production
Water quality is a particular problem during the dry season when water flows are low and also when rice farmers discharge water containing pesticides and fertilizers from their rice fields (Tung et al., 2004).
Basa should be able to adapt to a small increase in water temperature (average of 0.79oC, Eastham et al., 2008) but this increase may cause an increase in animal metabolism leading to an increase in feed input which may increase the requirement for fishmeal and trash fish. Increased storm and typhoon frequencies and intensities may result in financial losses and loss of livelihood which will impact on poor farmers.
|Contributors: The information on this page was originally compiled by Choo Poh Sze. Additional contributions have been made by ……. . The information has been reviewed by …..|