The Common Fisheries Policy is surrounded by an extensive system of rules (mainly consisting of quotas) to protect the environment from overfishing. Despite these rules, the cod is becoming increasingly rare in the North Sea resulting in drastic shortages in countries such as Canada and the United Kingdom. Strict fishing rules are the main reason for Norway and Iceland to stay out of the European Union (and out of the Common Fisheries Policy). Price guarantees and subsidizations of fishermen are implemented in the same way as agricultural subsidies are. Bluefin tuna is also a problem. Global stocks of the species are overfished with extinction in the wild a possibility in the near future. This also has the negative effect of threatening their traditional, natural predators.