By Sophie Kevany for Sentient.
Broadcast version by Suzanne Potter for California News Service reporting for the Sentient-Public News Service Collaboration
Fish, once a Friday penance for many, has recently become the "good meat" poster child. Fish farming has been touted as a way to help protect wild marine animals and, by some, even a way to feed the world. Yet a new study in Science Advances makes the case that farming fish comes at a much higher cost than previous estimates suggest, because of how much aquaculture relies on wild fish. According to the researchers, the total mass of wild fish required to produce farmed fish could be 536 percent higher than previous estimates. The drain on wild fish populations can in turn make it harder for vulnerable communities to find food. One of the core arguments for farmed fish - the idea that it protects wild fish by leaving them in the sea - ignores the fact that aquaculture relies on feed made from wild anchovies, sardines, herring, mackerel and other fish that many coastal nations rely on for sustenance.
The field of fish farming is no stranger to criticisms: overcrowded pens; poor fish health; inhumane killing methods; pollution; plastic waste from nets used to create pens, as well as diseases (spread by escaped farmed fish) that cause health problems for wild fish populations.
Nonetheless, the practice is growing. Farmed fish production is expected to have expanded by over 17 percent between 2022 and 2032, according to the United Nations Food and Agriculture Organization. By 2050, global demand for fish is expected to nearly double, thanks in part to an ever-increasing output of farmed seafood. Over a similar period, demand for fishmeal - the feed carnivorous farmed fish like salmon, trout and bass rely on - is projected to grow over seven percent by 2030.
"This is a hot topic in academic circles, but I don't think the public understands how fish farming works, especially in terms of its reliance on wild fish," Spencer Roberts, an environmental science and policy researcher at the University of Miami and a co-author of the new study, tells Sentient. In reality, says Roberts, aquaculture has simply shifted pressure from one set of fish to another.
The need for fish feed is creating problems for people too. "When we hear about fish farming feeding the world, it's not true. The reality is that it's starving people...in places like West Africa where 'reduction fisheries' are taking their fish," says Roberts, and selling or using them to turn into fishmeal. "Subsistence fishing communities are literally starving and being forced to emigrate," Roberts adds.
Part of how the aquaculture industry sold itself as the more sustainable option is thanks to what's known as the fish-in-fish-out ratio - the measurement of how many wild fish it takes to feed farmed ones. This figure, in essence, compares the number of how many wild fish are used as feed for fish farming, versus how many come out to feed humans. The calculation is used by the industry to demonstrate its efficiency, and therefore, its sustainability. It's used to make the case for how large a role it should play in a future with a growing global population, increasing planetary warming and shrinking natural resources, like farmland to grow food.
By focusing only on the ratio, Roberts and his co-authors argue, the true number of wild fish used to feed farm ones ends up obscured - indirect deaths are ignored, essentially - while outputs are maximized. This creates a misleading measurement.
There are a number of ways this plays out, but here's one example: so-called fish trimmings. Trimmings, which are the parts of the fish people don't traditionally eat (heads, tails and so on), are conventionally classified as by-products and subtracted on the basis that they are not wild fish. But according to a representative from The Marine Ingredients Organizations, only about 20 percent of trimmings for fishmeal come from farmed fish. The other 80 percent is from wild fish.
Once you adjust the calculation for the fish trimmings and other factors, the study finds, the volume of wild fish used to feed farmed fish could be over 300 percent higher than standard estimates. Taking other factors into account - when farmed fish that don't eat fishmeal are excluded, and indirect mortalities like slippage are included - it's even more dramatic. The total wild fish mass, according to the study, could be 536 percent higher.
It is not yet possible to convert the study's new percentage estimates into wild fish numbers, but Roberts says researchers working on the question believe reduction fisheries account for most fish taken from the ocean each year, killing over a trillion wild animals. These are animals who could otherwise be maintaining ocean health simply by staying in the sea, or helping to feed vulnerable populations.
Responses from fishmeal trade bodies to the new study varied, with the Marine Ingredients Organization favoring "a shared metric system" of lifecycle assessments, rather than fish-in-fish-out, and linking to a study that supports these as "the pathway to improved sustainability for all feed ingredients." A life cycle assessment quantifies the environmental impacts of a product, system or service from beginning to end.
The Federation of European Aquaculture Producers' general secretary Javier Ojeda was more upbeat about the study, saying its average ratio confirms that farming of fish reliant on fishmeal "is a net producer of aquatic food [which] should be heralded as great news," rather than a way to "demonize" it.
The Problem with Dewilding the Ocean
Fish farming creates another problem: dewilding. Separately, another new study finds mariculture - fish farming that takes place in the sea - is contributing to oceanic dewilding. Dewilding is a term for prioritizing human interests over ecosystems and, essentially, destroying the natural or wild world. Fish farms pollute the ocean too, with fish feces and uneaten food from farms creating excess nitrogen and phosphorus that can lead to algae blooms, depriving the water of oxygen.
The study looks at different dewilding categories, one of which is conceptual dewilding. Conceptual dewilding is a category that deals with human perceptions, which can set the stage for uncontrolled exploitation, says Becca Franks, co-author and assistant professor of environmental studies at New York University.
"The ocean is less explored than the moon... [but] as we map it for more places to put farms in and start to see it as a place to extract more resources from, the less we see it as a wild place, and the more we are going to be casual about destroying it," Franks tells Sentient.
Findings by Roberts and his team that aquaculture's dependence on wild fish is underestimated, are, Franks says, an example of "this rough, casual" approach to marine environments, and evidence that we are "not looking at the ocean as a wild space that should be approached with respect and caution."
Franks offers an example of humanity turning from a rough approach to a respectful one: whales. "We used to see them as floating oil reserves ...[but] with enough organizing and attention to who they actually were ... and allowing a bit of poetry to come in ... [we have] completely changed the way we think about whales, and it has allowed them to do better."
The bottom line, according to Franks, is that the critical role of oceans in storing carbon and mitigating climate change means we should take a very careful look at what kinds of aquaculture we want to proceed with, adding, "the details really matter."
Sophie Kevany wrote this article for Sentient.
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June is World Oceans Month and California environmental groups are highlighting advances in zero-emission shipping.
International shipping emits more than 1 billion tons of carbon dioxide every year, and 40% of U.S. container shipping passes through the Ports of Long Beach and Los Angeles.
Grace Healy, deputy director of the climate program at the nonprofit Pacific Environment, said it contributes to climate change and the resulting air pollution can shorten life spans by up to eight years in neighborhoods near the ports.
"Children in communities near these ports like Wilmington, San Pedro, West Long Beach, they face dramatically higher rates of asthma, bronchitis and cancer risk that's linked to diesel emissions," Healy explained.
California is a leader in clean shipping and passed a rule in recent years to require ships to plug in while onshore and shut off idling engines. Another mandate led to the first electric tugboat in San Francisco and a zero-emission ferry in San Diego. Shipping giant Maersk now runs a container ship on methanol.
Healy added in the next few years, the Golden State plans to tackle regulations on pollution from container ships.
"The California Air Resources Board has also stated they are going to work on an in-transit rule for oceangoing vessels," Healy noted. "That's really exciting, because those container ships are really, really dirty."
The future is uncertain for the federal Clean Ports Program, which supports the transition to zero-emission shipping. Money awarded last fall before President Donald Trump took office should be safe but the U.S. House of Representatives recently voted to gut the program as part of the Republican funding package known as the "One Big Beautiful Bill Act." The Senate version, which has yet to get a vote, appears to leave the language out.
Disclosure: Pacific Environment contributes to our fund for reporting on Climate Change/Air Quality, Energy Policy, and Oceans. If you would like to help support news in the public interest,
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By Seth Millstein for Sentient.
Broadcast version by Suzanne Potter for California News Service reporting for the Sentient-Public News Service Collaboration
The global population is projected to hit at least 8.5 billion people by the end of the decade. As more of us become aware of the disastrous environmental impacts of livestock production, some climate-conscious consumers are turning to seafood as an alternative to meat. But the seafood industry has its own problems, as the rise of overfishing - and its harms - has made clear.
"Overfishing is a serious global problem, threatening ocean wildlife and biodiversity, as well as seafood supplies," Dr. Beth Polidoro, Director of Research at the Marine Stewardship Council, told Sentient in a statement. "And unfortunately, it's a problem that's increasing, and has been for several decades."
Seafood consumption has risen dramatically since the mid-20th century: Between 1961 and 2021, the average person went from eating around 20 pounds of seafood every year to around 44 pounds, according to Our World in Data. Since then, commercial fishing has become a $229 billion industry, and according to a 2019 study, between 1.1 and 2.2 trillion fish are caught every year.
But as our appetite for seafood has increased, so has the frequency of overfishing. Between 1974 and 2017, the share of the world's oceans that were overfished jumped from 10 percent to a little over 34 percent, according to the Food and Agriculture Organization of the United Nations. Marine ecosystems around the world have suffered as a result.
But what exactly is overfishing, why is it such a big problem - and what can be done about it? Let's dive in.
What Is Overfishing?
Broadly speaking, overfishing is when fish in a particular region are caught at a faster rate than they can repopulate. In theory, this could ultimately lead to the extinction of the species, although in practice, it isn't clear that any fish species is confirmed to have gone extinct solely due to overfishing - although this might soon change, as we'll see.
Overfishing is directly related to the concept of yields. For any fish population, there's an "ideal" amount of fishing that maximizes the number of fish that can be caught in the long-term. Overfishing is simply when the fish in a region are caught at a faster rate than this amount.
"If you don't fish at all, you obviously don't get any long-term catch," Ray Hilborn, professor at the University of Washington's School of Aquatic and Fishery Sciences, tells Sentient. "If you fish too hard, you get very little long-term catch. And in the middle is this theoretical sweet spot that produces what's called 'maximum sustainable yield.'"
Hilborn says that in general, the maximum sustainable yield of a given fish population is "roughly equal to the fraction of fish who would die from natural mortality." For example, if 20 percent of the fish in a certain population would die from natural causes over the course of the year, this implies that fishers shouldn't catch more than 20 percent of that fish over that same period of time.
In contrast, you can look at the overfishing that occurred on Canada's northeast coast throughout the 20th century. Canadian cod was harvested so over-aggressively that by 1992, the region's cod population had fallen to less than one percent of its historic norm.
To ensure the species wasn't wiped out completely, the Canadian government announced a moratorium on cod fishing in the region, a decision that resulted in 30,000 people losing their jobs. And yet, the cod population in the area still hasn't recovered.
Overfishing is often grouped under the larger umbrella of illegal, unreported and unregulated fishing, (or IUU), by scientists, academics and policymakers.
What Are the Consequences of Overfishing?
Overfishing has a number of deleterious environmental impacts. Some of them, like bycatch, are inherent problems with fishing in general that are exacerbated by overfishing practices; others, like trophic cascades, are specifically caused by overfishing.
Ecosystem Destruction Due to Overfishing
Ecosystems involve a complex web of interactions between different species, and in a healthy ecosystem, these interactions naturally balance themselves out in a sustainable way. If predators become too populous, there won't be enough prey to feed them, so some of the predators will die off, which then gives the prey species time to repopulate. This repopulation gives the predators more access to food, thus allowing their species to repopulate, and so the cycle repeats itself.
Overfishing disrupts this natural process, and the consequences can be varied and far-reaching.
Take, for instance, the relationship between parrotfish, coral reefs and algae. Algae thrives in coral, but when it's allowed to grow unchecked, it can damage and kill the coral species. Luckily, parrotfish dine on algae, and so by simply going about their lives, they play an accidental but very important role in maintaining the health of coral reefs.
But when parrotfish are overfished and their population dwindles, this check on algae growth is removed, and the coral reefs suffer. This isn't just hypothetical: A study published in 2015 found that overfishing of parrotfish and other "grazers" has been a primary driver of the steep decline in the health of Caribbean coral reefs over the last 50 years.
This type of phenomenon, in which a change in a predator's population has a downstream effect not only on its own prey but on other species as well, is what's known as a trophic cascade. And overfishing has caused a number of trophic cascades.
The overfishing of sharks on the Atlantic coast led to a collapse in scallop populations, for instance, because sharks eat clownrays and clownrays eat scallops. Overfishing of cod and other sea urchin predators has helped degrade kelp forests, which is an especially big problem given the many environmental benefits that kelp provides.
One of those benefits is the absorption of carbon dioxide from the atmosphere, which brings us to another dire consequence of overfishing: rising global temperatures.
Overfishing Causing Climate Change
The idea that overfishing can exacerbate climate change might sound counterintuitive; after all, what do the number of fish in the sea have to do with the temperature outside? As it turns out, quite a bit.
The ocean absorbs a massive amount of carbon dioxide from the atmosphere: around three billion metric tons every year, or one-third of all global emissions. What's more, the ocean absorbs more carbon than it releases, which makes it a carbon sink - the world's biggest, in fact. Because carbon dioxide is one of the primary greenhouse gasses, the ocean plays an enormous and crucial role in slowing the rise of global temperatures.
But overfishing has diminished the ocean's ability to absorb carbon. That's because ultimately, it's the creatures in the ocean who are sucking up all of this carbon.
The process begins when phytoplankton at the ocean's surface absorb carbon dioxide from the air. These microscopic creatures are then eaten by zooplankton and other larger species, who absorb the phytoplankton's carbon, and so it goes throughout the ocean's food web - all the way up to whales, who can store up to 33 tons of carbon dioxide over the course of their lives.
This is an effective form of carbon storage, because the carbon remains in the ocean and out of Earth's atmosphere even after the fish die - unless, of course, the fish are caught by humans and removed from the ocean, in which case all of that carbon is released back into the air. Overfishing greatly exacerbates this phenomenon: According to a Sentient analysis, overfishing results in an additional 5.6 million metric tons of CO2 being released into the atmosphere every year.
Bycatch Due to Overfishing
Bycatch is what happens when fishers accidentally catch, injure or kill species that they weren't intending to catch. Common victims of bycatch include dolphins, sea turtles and over 200 other species that are protected, endangered or threatened.
The sheer extent of bycatch can't be overstated: It's been estimated that over 40 percent of all fish caught annually are actually bycatch. What's more, bycatch results in the death of more than 650,000 marine mammals - that is, aquatic creatures other than fish - every year.
Hurting Local Fishing Communities
Many coastal communities around the world rely on a healthy supply of local fish to feed themselves. Overfishing and other forms of illegal, unreported and unregulated fishing have hurt these communities in a number of ways, and it's often developing countries that suffer.
In Sierra Leone, for example, overfishing in coastal waters has forced local fishers to travel further and further into the sea to catch fish, exposing them to increasingly dangerous weather conditions. In 2022, Sierra Leonean fishers told the Guardian that they're struggling to feed their families thanks to the dearth of fish caused by overfishing.
Much of the time, the overfishing causing this is carried out by foreign nations. In Japan and South Korea, for instance, more fish is caught by other countries' vessels than by domestic fleets. In Sierra Leone, most of the large trawlers used to harvest fish are owned by European and Asian companies, according to the United Nations, and 40 percent of industrial fishing licenses in the country are owned by Chinese vessels.
Possible Extinction Due to Overfishing
As mentioned earlier, no fish species is confirmed to have gone extinct solely because it was subject to overfishing. But that may not always be the case: A 2021 study by the World Wildlife Foundation concluded that one-third of all shark, ray and chimaera species are currently at risk of going extinct thanks to overfishing.
How Can We Stop Overfishing?
End Harmful Fishing Subsidies
Governments around the world spend a lot of money subsidizing their respective countries' fishing industries. Though some of these subsidies are benign, others have been blamed for incentivizing overfishing and contributing to all of the above problems. For instance, many governments subsidize or discount the fuel for shipping vessels, allowing them to fish longer, harder and farther away.
The world's governments spend over $20 billion on what researchers call "harmful fishing subsidies" every year, according to a 2019 study in the journal Marine Policy. Eliminating, or even substantially reducing, these subsidies would go a long way to curb overfishing, according to a range of experts and marine advocates.
Protect More of the Ocean
Marine Protected Areas (MPAs) are areas of the ocean in which legal protections have been established for conservationist purposes. The nature and degree of these protections vary, but many of them have been effective at reducing or eliminating overfishing within their boundaries.
However, MPAs only cover a miniscule portion of the ocean. According to the UN, less than nine percent of the ocean is protected by MPAs - and that's one of the higher estimates. The Marine Conservation Institute puts the number at around five percent, while a 2024 report by a group of NGOs claimed that, due to lax enforcement and weak protections in some MPAs, only 2.8 percent of the ocean is effectively protected from overfishing.
Regardless of which estimate is most accurate, the upshot is clear: Over 90 percent of the ocean is unprotected. Bolstering MPA enforcement and bringing more of the sea under legal protections - which the UN, to its credit, is currently attempting to do - would be another powerful check against overfishing.
Eat Less Seafood
One factor driving overfishing is that consumers are increasingly developing a voracious appetite for seafood. Some coastal communities are dependent on fish for their diet, but the rest of us can be mindful of overconsumption, and how it impacts wildlife, including fish and other marine life. One alternative: the many sources of plant-based protein that don't exact anywhere near the environmental cost of seafood (or meat, for that matter).
The Bottom Line
Although it has become increasingly popular to think of fish as a sustainable alternative to meat, the far-reaching environmental, animal and human impacts of persistent overfishing throws a wrench into that narrative. If industrial fishing operations continue at their current pace, so will overfishing - at high cost to marine habitats and our ability to stave off the worst effects of global warming.
Seth Millstein wrote this article for Sentient.
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