When I was a boy I saw the waves of the Atlantic Ocean turn mercury-silver and the water boil as mackerel herded bait fish into a small bay and onto a beach on the west coast of Ireland. It is a picture of a bountiful ocean that has remained with me to this day. The oceans provide 2.9 billion people with at least 15% of their annual protein requirement and more than 100 million people are involved in the fishing industry with more than half a billion dependent on the sector. Annual global fish trade is worth $92 billion and the seafood industry as a whole probably more than $200 billion. Fishing is a lucrative business as well as a critical food security and livelihood issue, especially in the developing world. Yet all is not well in the oceans, the largest ecosystem on the planet Earth, and reversing the worrisome developments threatening to empty the oceans will require a concerted, global effort.

After the Second World War there was a massive expansion in fishing as the distant-water fleets of the industrialized nations cast their nets and lines across the oceans. Acoustic and navigation technologies allowed us to find fish wherever they are, and to catch them in increasing quantities by deploying greater numbers of more powerful and larger fishing vessels with more and more sophisticated fishing gear. The result of this was that in the 1980s marine fish catches began to stagnate and are now in decline. Many iconic and economically important fisheries, such as the northwestern Atlantic cod, have been lost. The large predators of the oceans – tuna, billfish and sharks – are simply disappearing with populations falling to 10% or less of their unfished abundance. For some of these species extinction is a real prospect. What has gone wrong and can it be fixed?

Depletion of fish stocks has been driven by open access to fisheries, encouraging a damaging “race to fish” amongst fishers, as well as massive overcapacity in fishing fleets. Thanks to government subsidies, fishers continue to exploit depleted or unproductive stocks. Each year governments spend about $20 billion on harmful fishing subsidies. Global fleet capacity too has grown to about twice that required to harvest current fish stocks, undermining efforts to sustainably manage fisheries. Efforts to reduce global fishing fleets are often met with fierce opposition from fishers and supportive politicians. Using short term socioeconomic justifications, politicians have set fishing quotas way above those recommended by scientists. In Europe, quotas have been 42-57% higher than scientific recommendations and as a result 80% of European fish stocks are fished beyond sustainable levels compared to an average of 25% globally.

To exacerbate the situation 11 – 26 million tonnes of fish, worth $10 - $23 billion per year are caught illegally. Parts of the developing world, with poor capacity to manage fisheries, such as east and west Africa are particularly hard hit by this piracy. In some cases, such as in the blue fin tuna fishery in the Mediterranean, blatantly illegal fishing and overfishing practices are encouraged by the extraordinary prices that some fish can fetch. Single blue fin tuna have been reported to have been sold in sushi-loving Japan for more than $100,000.

Worryingly, fishing has other effects on marine ecosystems. Overexploitation of target fish stocks changes the structure of marine ‘food-webs’ and the ecosystem of which they form a part. In the worst cases, overfishing can interact with other human interference, exacerbating climate change effects. Overfishing of grazing fish such as parrotfish and surgeonfish from coral reefs decreases the resistance of the reefs to the effects of mass coral bleaching, which has been happening as a result of increasing sea surface temperatures since the late 1970s. In coastal waters off the United States and in areas such as the Black Sea, outbreaks of invasive jellyfish and the development of dead zones, areas of the sea where a lack of oxygen kills almost everything, can be related to the combined effects of overfishing, pollution from agricultural run-off, shipping and climate change.

By-catch – the amount of unmanaged and wasted catch by fishing trawlers, another effect of over-fishing – is estimated at a staggering 38.5 million tonnes, about 40% of marine fish catches. By-catch includes many iconic marine predators, such as oceanic seabirds and sharks and has reached levels that threaten these species with extinction. The impact of bottom fishing gear on seabed communities of ancient corals, sponges and other species has become a major global concern, especially in the deep ocean where such animals may live for 4000 years and have little chance of recovering from fishing impacts.

Given the critical importance to future generations of the oceans for food security and the other services they provide, such as regulating the climate and the Earth’s major nutrient cycles, we must change the way we manage fisheries. It may come as a surprise, but we already know how to do this. One way to improve the sustainability of fisheries is to give ownership of the resource to the fishers. This is not a new idea and has been practiced since ancient times in the western Pacific where fisheries were managed through territorial use rights or customary marine tenure.

Fishers are allocated a set proportion of the total allowable catch (TAC) and these quotas may be transferable (sold onto other fishers) or non-transferable. Such systems tend to reduce fleet overcapacity and make fisheries more economic, reducing the need for subsidies. Because they secure harvesting rights to fishers they also encourage long-term stewardship of marine resources and greater cooperation between fishers and fisheries managers.

Governance of fisheries must improve globally through the strengthening of international law and the improvement of the performance of states and regional fisheries management organizations (RFMOs) charged with managing fisheries. Managers must have a comprehensive understanding of what fish are being caught and are being discarded; the ecosystem impacts of such fishing activities and politicians must follow scientific advice on catch limits to sustain fisheries over the longer term. These are obligations under international law and are simply not being met. Recent news that the FAO has successfully negotiated a new international agreement on port state measures to combat landings of illegally caught fish is welcome. However, tackling illegal, unreported and unregulated (IUU) fishing will require further efforts.

Finally, we have to change completely the approach to ocean management. It is possible, through technical measures to reduce by-catch in many fisheries and through careful consideration to avoid management measures that encourage discarding of unwanted or low-value catch. However, the adoption of marine protected areas on a large scale across the oceans offers the greatest opportunity not only to improve fisheries, but also to maintain the species diversity and function of marine ecosystems and prevent the catastrophic collapses like the disappearing Atlantic cod that we are witnessing. Studies have demonstrated that such protected areas rapidly lead to the recovery of fish populations and increased survivability of fish to a large size. The improved reproductive capacity of such populations soon leads to an “overspill” effect whereby fish stocks outside of the protected zones increase, benefiting fishers by increasing catches. The benefits to the marine environment are profound with recovery of seabed habitats from the impacts of bottom fishing and increased abundance and diversity of marine species. Such effects have been seen in marine reserves from the tropics, for example in St Lucia, and in temperate regions, such as George’s Bank in the Gulf of Maine.

Life began in the oceans and it behoves us to do our best to protect the life-sustaining oceans and their riches.