- Fifty years from now, in 2075, global ocean temperatures are forecast to rise by between 2° and 5° Celsius (3.6° and 9° Fahrenheit). Warming is already reshaping fisheries worldwide, and even more dramatic changes are expected as fish largely move to cooler latitudes.
- These fish migrations will change ecosystem patterns and will likely have unexpected consequences even in places far from the fish themselves. They also may devastate fishing communities, both on a socioeconomic scale and a social one.
- However, there are potential solutions to avoid the most catastrophic effects for fishers and ecosystems alike, including setting aside some ecosystems as marine protected areas, changing fisheries management strategies and retraining communities to provide supplemental income.
Lake Chad is nearly 1,130 kilometers (700 miles) from the ocean, but Nwamaka Okeke-Ogbuafor fears it is a preview of what’s ahead for African and other tropical fisheries.
Straddling four countries on the southern edge of the Sahara Desert, Lake Chad began drying up dramatically during a series of droughts in the 1970s and ‘80s. While the lake stopped shrinking in the 1990s — and it appears to be stable or even growing over the last 20 years — many fishing communities on the lake never recovered. Facing poverty and starvation, some former fishers and their families live in U.N.-funded camps for displaced people, which are running out of aid. Some struck out for a new life in other countries. Others joined Boko Haram, an Islamic insurgency organization, in a final act of desperation.
“Communities are no longer cohesive — it’s a total disaster,” says Okeke-Ogbuafor, a marine social scientist focusing on tropical African fisheries. “It’s not just about food poverty, it’s the erosion of community and cultural knowledge.”
Fish provide essential protein for an estimated 3.2 billion people across the world. In some developing tropical countries, fish can make up some 70% of the diet. But over the next 50 years, warming waters are certain to upend fishing communities — and rewrite the rules of ecosystems and industries worldwide.
Mongabay asked five experts how fisheries will change by 2075, and what solutions could help prevent the worst outcomes.
Hot fish to go
Climate change is unpredictable, but there’s one pattern experts agree on: Globally, fish will move from lower latitudes to higher ones. The reason for this is simple: Physiologically, marine organisms have evolved to live in relatively narrow temperature bands. As ocean temperatures rise, creatures will migrate if they can, which largely means moving away from the warm equator and towards the cooler poles.
This basic pattern will spiral out in multifaceted ways. In the tropics, this global migration causes Okeke-Ogbuafor’s concern for local fishing communities; her research in West Africa is already showing fishers under strain as species depart their historic range. Fishers have been telling her that the Indigenous knowledge of where to catch, as well as when to go fishing safely, no longer applies.
Fishers now need to travel further to find fish. They also have to spend more money on fuel than they’ll get for their meagre catch.
“The amount they invested, they always lose,” Okeke-Ogbuafor says.
And because there are fewer fish, Okeke-Ogbuafor says, she sees fishers increasingly flouting local regulations that are aimed at reducing overfishing.
“Some of them go to where fish lay their eggs and catch baby fish to supply to companies that grind them and export them to Europe for fish meal,” she says. “They’ll catch anything. It’s survival — whatever you lay your hands on.”
Okeke-Ogbuafor’s expectation for these fisheries in 2075 is a grim one: more of the same pattern, and worse, if governments don’t step in. Fishers will need to be retrained in different jobs or provided with supplementary income. So far, Okeke-Ogbuafor doesn’t see momentum for that kind of adaptation.
“In most of Africa, we are not even prepared. We don’t have the finances, we don’t have the alternatives,” she says.
Similar patterns are expected across the global tropics. A 2022 study predicted that 23% of fish stocks shared between countries would change their historic habitats by 2030, and 45% by 2100. The Caribbean, Latin America, Oceania and South Asia are expected to see these shifts sooner than others. Fisheries in partially enclosed seas like the Mediterranean, with nowhere to flee as it warms, may go locally extinct.
Shakeup at the poles
At the poles, ecosystems will see the other end of this pattern as fish will move from warmer ecosystems into cooler waters. As parts of the Arctic and Antarctic become warmer — and ice-free for more of the year — these movements have already spurred small-scale squabbles among northern nations.
But despite the chatter over potential new fisheries, Maxime Geoffrey, a research scientist at Canada’s Marine Institute of Memorial University of Newfoundland, expects that migrating fish will still face limiting factors due to the poles’ extremes. Fish from lower latitudes may struggle with the poles’ daylight and darkness extremes, especially if they use light as a cue to feed. Reproduction poses another challenge: Most polar fish spawn in winter, so that they can take full advantage of the brief, glorious pulse of food available during the summer. Species evolved to breed during warm months, which are often accustomed to food being available in autumn, may miss out on summer’s fleeting buffet.
Even if the poles see warmer summers, winter temperatures still promise to be a shock to lower-latitude species.
“If it’s cold enough to kill them for just one month instead of three months, it still kills them,” says Geoffrey, whose research focuses on Arctic marine ecology.
All of this means that polar seas will probably change more slowly than the tropics, protecting them from fishing pressure. The high seas of the central Arctic Ocean are also currently under a 16-year international fishing moratorium, giving researchers time to understand how it’s changing.
“There’s strong interest by many countries, but the reality is there are probably not viable stocks in that region in the short to mid-term,” Geoffrey says. Instead, he says, he expects that the biggest changes by 2075 will be in places with established fisheries: like the Barents Sea, fished by Norway and Russia, and Baffin Bay, fished between eastern Canada and Greenland. Rather than all-out invasions from southern species, Geoffrey says, he expects that uncommon species will become more dominant. He says he already sees this happening with species like capelin (Mallotus villosus), Arctic cod (Boreogadus saida) and Acadian redfish (Sebastes fasciatus).
Management challenges
Fish don’t follow borders. However, for humans, borders are essential in divvying up access to fish. As climate change re-distributes fish, it will pose a particular challenge to fisheries management: The science and policy to explain to people how much they can fish, when, and where.
“Everything is set up … based on the patterns we’ve seen historically, so there’s going to be a need to be able to adapt decision-making,” says Graham Pilling, the head of the Secretariat of the Pacific Community (SPC)’s Oceanic Fisheries Programme (OFP), which provides scientific advice about tuna and other migratory oceanic species to Pacific island countries and territories. This role includes forecasting the abundance and movement of these fish stocks under climate change. As Pilling says, “tuna are going to be in a very different location to where we see them now.”
Tuna landings are already on the decline as tuna shift their migration patterns in response to climate change — and scientists project tuna catches will drop by more than 30% by 2050. Many different nations fish these stocks, and in the western and central Pacific, licensing fees for foreign fisheries provide significant revenue to Pacific island nations. Much of this tuna is also processed in Pacific island countries and territories.
Under climate change, tuna will increasingly move into the high seas, where fishing rights are managed under international agreements. This poses a serious problem for island nations that rely on tuna money. Tuvalu, Tokelau and Kiribati, for example, count on tuna fishing for at least 50% of their national revenue.
At the SPC, Pilling says that climate change is now on the agenda for every meeting, and his work at the OFP is partially focused on spotting climate change indicators. He says that the decision-making processes about managing fishers will need to adapt as climate change causes further shifts.
“[Management is] beginning to adapt, but it’s not going to be an easy process,” he says.
Indeed, several of the experts say countries may need to move away from traditional fisheries management, which is largely focused on achieving the maximum possible catch. Instead, managers could introduce ecosystem-based management approaches, which base their quotas on the interactions between species and their environment. This includes adaptive management strategies: For example, if an area experienced a marine heat wave, quotas for temperature-sensitive species would need to decrease.
Vicky Wing Lee Lam, a fisheries economist with the Sea Around Us initiative of the University of British Columbia, Canada, also highlighted community-based management, which gives fishers and coastal communities a larger role in managing marine resources in their own backyards. In British Columbia, community-based management increasingly incorporates traditional ecological knowledge (TEK) from local First Nations tribes.
But Okeke-Ogbuafor cautions that community-based management strategies won’t work everywhere. She says she has seen that managers in the countries she studies can be particularly vulnerable to social pressures.
“A fisherman would come and say, ‘if you want me to pay fines, or not fish with a monofilament net, then how do I feed my daughter?’” she explains. “When someone says, ‘I don’t have food in my house’ — these people know each other, and they can’t actually impose the rule.”
Distant ripples
Like a rock dropped in a pond, the impact of changing fisheries won’t only be felt in the places where change is acute: They’ll ripple outward, touching places all over the world.
For example, Lam says she expects to see the anchovy fishery in Peru decline over the next 50 years, as these small, high-protein fish struggle to adapt to warmer waters. That decline will be felt oceans away in Norway, where a growing aquaculture industry relies on anchovy for fish meal. The search is already underway for alternate protein sources.
Lam also gave the example of tuna canning, which directly employs more than 20,000 people in Spain alone, and which could become vulnerable as Pacific tuna landings drop.
Though many ecosystems and communities are already feeling the effects of climate change, experts say that the worst potential effects can still be avoided. However, doing so will require major shifts — and fast.
The very first priority is getting overfishing under control to make fish populations more resilient, says Enric Sala, a marine researcher and founder of National Geographic’s Pristine Seas Foundation. He says this particularly applies to industrial fishing, carried out by enormous, highly efficient vessels that stay at sea for months and catch thousands of tons of fish.
“Industrial fishing as it is today is totally unsustainable,” Sala says. “The future of fisheries has to be reducing industrial fishing … and resuscitating small-scale, artisanal fisheries, which are dead in many places.”
The Food and Agriculture Organization (FAO) of the U.N. estimated that, as of 2024, one-third of the world’s assessed fish stocks were overexploited. An even larger proportion are fully exploited, meaning they cannot take any more pressure before becoming overfished.
Sala’s Pristine Seas Foundation is focused on a solution to alleviate this pressure: Marine Protected Areas (MPAs), areas that limit or ban fishing entirely. Though it seems contradictory, Sala says that MPAs not only make an ecosystem more resilient to climate change but can also boost the catch of local fishers.
“Even in an increasingly warm ocean, no-take areas are still maintaining a greater biomass, and we see from our studies that they are more resilient to marine heatwaves,” Sala says. He gives the example of the protected reefs in the Southern Line Islands in Kiribati: An El Niño event killed half of the corals there in 2015-16, but when Sala’s team returned five years later, the reefs looked as though they had almost entirely rebounded — while nearby unprotected areas saw no such recovery.
The booming populations in these protected areas then “spill over” into unprotected areas, Sala says, boosting the fishing returns of nearby communities.
“We have hundreds of examples of communities that have decided to protect an area…and then fish responsibly around it,” he says. “They will be catching the same or more, because of the spillover and, because they will be fishing locally, they will increase their profits.”
MPAs are not silver bullets, however. While experts see them as a promising tool, they say MPAs will need adaptation to make them fit individual ecosystems and communities. For example, Pilling cites mixed results in scientific literature over whether MPAs benefit highly-migratory fish, like tuna. And Okeke-Ogbuafor says that locals may simply disregard a no-take area if the community lacks resources for monitoring and enforcement.
With limited resources in mind, one of Okeke-Ogbuafor’s current research projects is training vulnerable fishers to set up aquaculture operations as another form of income. She says she’s found that working with fishers directly on these projects has produced promising results: When she learned in Sierra Leone that farmed fish were perceived as less nutritious, she worked with farmers to develop a locally made feed they trusted. Feedback from fishers also led their project to use collapsible tanks, which are easier to move and dismantle when not in use, and place tanks under shade trees to keep water temperatures lower.
However, she also raises the prospect that, as fish migrate away from poor tropical countries, more northerly countries that benefit might participate in a profit-sharing agreement to support those who have lost their livelihoods. Pilling says she’s been hearing similar conversations among Pacific island communities. These discussions include providing Pacific island nations special access — whether to migrating fish themselves, or to revenue from their exploitation — even as they move into the high seas, and allowing these nations to maintain fishing rights in their national waters even if their islands disappear due to sea level rise.
“This is what they call a climate justice issue,” Pilling says. “And ultimately it makes sense … considering that the outcomes are dire for Pacific islands, yet the causes [of climate change] are not by the Pacific islands.”
Banner image: Yellowfin tuna, one of the seven major commercial tuna species, attempt to outswim a seine net in the Seychelles. Fishing is the second largest industry on this small Pacific Island, and like many other Pacific Islands, it faces major revenue losses as tuna shift their migration patterns into the high seas due to climate change. Image by Marc Taquet / Ifremer.
Citations:
Food and Agriculture Organization (FAO). (2024). The State of World Fisheries and Aquaculture 2024. doi:10.4060/cd0683en
Erauskin-Extramiana, M., Chust, G., Arrizabalaga, H., Cheung, W.W.L., Santiago, J., Merino, G., & Fernandes-Salvador, J.A. (2023). Implications for the global tuna fishing industry of climate change-driven alterations in productivity and body sizes. Global and Planetary Change, 222, 1040-1055. doi:10.1016/j.gloplacha.2023.104055
Palacios‐Abrantes, J., Frölicher, T.L., Reygondeau, G., Sumaila, U.R., Tagliabue, A., Wabnitz, C.C.C., & Cheung, W.W.L. (2022). Timing and magnitude of climate‐driven range shifts in transboundary fish stocks challenge their management. Global Change Biology, 28(7), 2312-2326. doi:10.1111/gcb.16058
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