Overexploitation of the planet’s fish has more than tripled since the 1970s, with 40 percent of popular species like tuna now being caught unsustainably. That’s why the United Nations is hosting its first ever Ocean Conference this week in New York, which will feature member states discussing how to meet the sustainable development goal on ocean health. The first order of business: An initiative involving nine of the world’s biggest fishing companies pledging to help stamp out illegal fishing activities, including the use of slave labor and overfishing. The companies, which have a combined annual revenue of about $30 billion, will also eliminate any fish from their supply chains that could have come from piracy or other illegal sources.