Closing the high seas to fishing could increase fish catches in coastal waters by 10%, compensating for expected losses due to climate change, finds a new Nippon Foundation-Nereus Program study published in Fish and Fisheries.

The high seas are those areas of the ocean outside the jurisdiction of countries; the high seas cover nearly two thirds of the ocean’s surface. These results could be seen by 2050 relative to 2000 and cooperatively managing the high seas fisheries would have similar effects.

“The oceans are interconnected. Many important fish stocks live in both the high seas and coastal waters,” says co-author William Cheung, Nippon Foundation-Nereus Program Director of Science. “Although the high seas may seem far from the coast, effective management of high seas fisheries could benefit coastal waters in terms of productivity and thus help reduce climate change impacts.”

The study used a computer model to project catches of 30 important fish stocks that occur in both the high seas and coastal waters under two CO2 emission scenarios and three high seas management scenarios.

Strengthening high seas governance would also increase the resilience of coastal countries to climate change, especially in tropical countries where there is a high dependence on fisheries for food and livelihood. Under a “business-as-usual” CO2 emissions scenario, disproportionate impacts of climate change on countries in the South Pacific, Indo-Pacific, West African coast and west coast of Central America include decreases of over 30% of fish stocks due partly to migration of fish towards cooler waters.

“The scenarios of closing the high seas may greatly reduce the issue of inequity of benefits and impacts among different countries under climate change,” says co-author Vicky Lam, Nippon Foundation-Nereus Program Fellow at UBC.

The authors note that impacts felt in tropical countries will still be high though, even under best-case scenarios. Adaptation measures, such as diversifying employment opportunities or fishing a different type of fish, would need to be introduced.