In a big change to fisheries, the wasteful practice of throwing fish overboard this month became illegal in waters of the European Union. Scientists believe the policy will incentivize vessels to adopt more selective fishing gear or strategies and eventually boost stocks. But in the short term, it could mean hardship for the industry and perhaps even compromise fisheries data, because almost all crews can discard fish without anyone knowing. More quota trading could also help industry cope. Last month, EU fisheries ministers increased pressure on nations to start trading quotas. Few expect all fishing vessels to obey the discard ban. Environmentalists want to toughen up enforcement by installing cameras on ships. Countries where discard bans have succeeded, including Norway and Iceland, have gradually introduced incentives, such as to develop the economic use of unwanted fish, and regulatory controls. Those steps lessen conflict, but can take decades to achieve.