Overfishing has been talked about and a concern to countries to an extent in the past but hasn't been a serious priority that countries have worried about. One of the biggest issues is that the regulation enforcement for fishing has been extremely lax which has to lead to overfishing, overcapacity and illegal, unreported and unregulated (IUU) fishing. Countries have been subsiding there fishermen in order to secure the market. Which has to lead them to overfish because they know economic loss from the fish they loss will be reimbursed in some sort of way.
WWF has now urged countries in the WTO to so stop subsidizing them to prevent further harm to the wildlife and the environment. Which in the past few years the fish population has diminished as well as the size of them. To further the issue the ecosystem life has diminished and has contributed to the negative effects of climate change. This problem isn't one to be easily solved because taking away the subsidies of the fishermen could harm the market. For some countries fish is their main food source as well as protein, so placing an international quota would harm smaller countries that depend on fish. There is no real solution that would fully benefit both sides of this issue.
References and further information:
http://www.military-technologies.net/2017/12/14/wwf-calls-on-wto-to-end-subsidized-overfishing-and-illegal-fishing/
https://www.worldwildlife.org/threats/overfishing
https://euobserver.com/environment/140270