A point of contention among scientists, though, is whether reefs are beneficial for the environment. Some studies say reefs can provide spots for fish nurseries and lead to increased populations, while other studies show artificial reefs merely draw fish from a large region to a focal point for fisherman to pluck them out of the water -- like fish in a barrel, only underwater -- exacerbating overfishing.read more here:
http://www.news-journalonline.com/news/outdoors/fishing/2010/06/28/ramping-up-reefs.html