The United Nations Conference on the Law of the Sea marks the threshold of a major transition in regimes governing the use of ocean fisheries. After 200 years of operation, the principle of the freedom of the seas for fishing is being abruptly dismantled and replaced by extended zones of national jurisdiction. The new acquisition of authority by coastal states will, in many situations, greatly facilitate the adoption of improved management techniques. But in most regions throughout the world, the authority over numerous stocks of fish will continue to be diffused among neighboring countries because of the migratory patterns of the stocks. Arrangements for the distribution of yields from these shared stocks, for the provision of information, the adoption of regulations, and enforcement will be extremely difficult to achieve and may become significant sources of conflict and waste for many years into the future.