Large-scale fish farming became widespread in the 1960s. Now, more than 30% of all sea animals consumed worldwide come from fish farms (measured by weight). Widely farmed species include carp, salmon, trout, tilapia, mussels and prawns. Government-backed research efforts are aimed at extending this list and commercially-farmed cod and tuna are now beginning to be produced. Fish farms can be based on land or at sea. On land, fish are raised in ponds or tanks.China is the world’s largest producer, but fish farming is also a significant industry in Peru, India, Indonesia and Chile. In the developed world, fish farming is particularly prominent in Norway, Canada and Scotland. Some environmental groups, such as Greenpeace, oppose fish farming and want it to be banned or severely restricted. However, supporters of fish farming argue that it is a cheap and sustainable way to provide healthy food to large numbers of people. At the time of writing (June 2006), governments have done little to restrict fish farming.