The oceans are perhaps the ultimate tragedy of the commons, and the fishing industry has defied effective regulation the world over. In part, that's because you can't stop the fish from, well, swimming, and even if you limit catches in one area, there's no guarantee for effective regulation in another. When a country grants licenses, foreign fishing companies often swoop in. Catch limitations can be difficult to enforce, especially in rural areas. Communities dependent on fishing are caught in a worsening cycle of being forced to go out further and fish for ever diminishing returns. So is there anything to do but abstain from eating fish altogether, or, perhaps, chow down on tuna with a side of fatalism?
One effort gaining ground is that of Marine Protected Areas (MPAs). MPAs place regulation and limitations on areas, rather than catches, making enforcement somewhat easier. It prevents harmful fishing practices, like trawling, and it allows fish a space in which to safely reproduce. A successful MPA acts like a sort of incubator, protecting flora and fauna from harm, the growth of which then spills over into surrounding areas.
Organizations like Marine Conservation Institute, Greenpeace, and the Ocean Conservancy point out, however, that the success of an MPA is not only dependent on effective enforcement, but on the site chosen. It's all well and good to declare a 100 mile zone 'no-fishing,' but if it's a barren dead zone, protection won't do much.
Countries would see greater returns, they argue, if biologically diverse areas are chosen. Far from harming the fishing industry, this practice allows for regeneration of catch. According to the Nature study referenced in a recent New York Times article, reserves are more successful if they are large (at least 100 square kilometers, or almost 40 square miles) and enduring (established for at least 10 years). The most effective reserves generally enforce a total ban on fishing and other activities harmful to marine life, like mining and drilling. Features that encourage isolation - like sand barriers - also help. MPAs with all of these characteristics contained 840% more large fish than comparable areas open to fishing, the study found.
MPAs will not solve the problem of depleting diversity in our oceans; that's a larger and scalier problem complicated by issues of climate change and ocean acidification, but it's seen better results than pretty much anything else we've tried - and that's worth supporting.