Marine Protected Areas boost fishing and tourism, with profits sometimes in the billions, according to the most comprehensive global assessment of its kind to date.

MPAs, or national parks at sea, are found in many of the world's oceans, with past research showing fully protected areas can help restore fish populations by 500 per cent on average, yielding bigger fish over time.

Now a new study of more than 50 protected areas in more than 30 countries in North America, South America, Europe, Africa, Asia and Oceania has concluded they also bring significant financial benefits.