EU regulators floated a series of ideas on Monday on how to control Europe's "black markets" in fishing quotas and help preserve stocks of key species like cod and hake that have been depleted by years of overfishing, according to Reuters. While markets in fishing rights exist legally across the EU, they differ widely -- with little transparency in how prices are set and agreed, either between countries or between individuals within the same country, the EU's executive Commission says. Part of the reason is that by limiting a country's annual quotas for catching individual species, making each government responsible for sharing that quota among its fishermen, a cash value is indirectly placed on the right to fish, it says. A company in one EU state can buy a vessel in another and pay extra for fishing rights there, which Brussels says makes it difficult to monitor activity across the bloc. "There are black markets for rights all round Europe. It would be better to be open and have more transparency," Alberto Spagnolli, head of the economic analysis unit at the Commission's fisheries department, told reporters.