http://www.fao.org/newsroom/en/news/2006/1000383/index.html
This study by the UN shows that wild catch is leveled off and that farmed fish now account for 43% of world fish consumption, up from like 13% in the 80s. The argument is that we have to grow farming to sustain increased demand for fish, and that the problem with that is the need for better feeding of the fish.