Policies that ignore or oppose market forces tend to deliver unexpected side effects stemming from the decisions and actions of those they affect. On the other hand, policies that take advantage of the ability of markets to allocate resources can increase the efficiency, sustainability and profitability of a fishery. These systems convert fishing possibilities (individual catch quotas) into fishing capacities (individual effort quotas) and may be most appropriate for sedentary species such as crab and lobster. The situation may also arise where fishers pay non-fishing right-holders for access. This can lead to conflict and disputes.