The population of North Sea cod stocks, that was once disastrously over-fished, is rapidly improving, according to scientists.
In the 1970s the cod catch from the North Sea peaked at 270,000 tonnes per year but after years of over-fishing that figure fell to just 44,000 tonnes in 2006, say the International Council for The Exploration of the Sea [ICES].
But those fears that the population was on the verge of collapse have now been relieved as after the species was placed on the endangered list, the annual catch of cod has risen to around 150,000, according to the ICES.
The fishing industry has worked hard to meet regulations imposed to protect fish stocks such as abiding by the quotas on how much can be caught and applying measures to avoid netting young, small fish below breeding age.
Marine biologists who work with fisherman say it is an example of an EU policy succeeding.
Fisheries biologist, York University, Bryce Stewart said: "The common fisheries policy itself was always pretty good but it wasn't implemented properly, we had rules being broken, we had quotas being set too high, now that it is actually applied properly - it's working".
Later this month fisheries watchdog the Marine Stewardship Council is expected to announce that stocks of cod in the North Sea are finally sustainable.
However despite the species no longer being endangered conservation efforts are still needed.
One challenge facing Brexit will be to draft and enforce regulations similar to the ones already in place.