Besides the problems encountered by
pond aquaculture, cage, and pen aquaculture also suffered from
such problems as escapees and feed of poor quality. To pursue
higher profits, fish farmers were always ready to shift from aquaculture
of low-trophic-level species (e.g., traditional aquaculture
species like Asian carps) to high-trophic-level species which will
rely on inputs of fish or other feed rather than ambient primary
production, imposing burdens and dangers to the environment and
ecosystem balance and health. More worse, to pursue high productivity