What does extraction mean in the context? Does it mean 'the things that are extracted from fish, that is, fish organs' or 'utilization'?
Although aquaculture occurs in a controlled environment, cases of escapes, contamination, and spread of disease have been documented, all of which may harm the natural ecosystem in the surrounding area. For example, studies in Chile have shown that escaped salmonids can colonize their new, nonnative environment, resulting in resource competition and potentially altering local ecosystem processes. Shrimp production in Asia and other parts of the world has resulted in the deforestation of mangroves and wetlands in order to create space for shrimp ponds. The cultivation of carnivorous fish depends on the extraction of wild fin-fish that are converted to meal for fish food. In some parts of the world, this has meant depleted stocks for local fishermen, who still depend on these species for a supplement to their diet or for income. Experts have recently recommended that native herbivorous or filter feeders be farmed, rather than nonnative carnivorous species, in order to avoid some of these potential problems. Another suggested solution is to farm exclusively in terrestrial, man-made tanks where all stages of production could be managed, including the disposal of waste.
