The seafood platter – past, present, and future By Gillen D’Arcy Wood

The Dutch Caribbean islands of Aruba and Curaçao are famed for their sun-kissed beaches. Just fifty miles to their east, the lesser-known Bonaire island is treasured by scuba divers precisely for its lack of beaches, bathers and tourist hotels. On Bonaire, one can dive from the shore, swim without effort across a narrow band of sand, then plunge instantly down to an immense coral wall – a world within a world. Like a technicolor movie in three dimensions, the ocean gardens of Bonaire full of bright corals and darting neon fish quickly overwhelm the senses. On my first Bonaire reef dive in January, 2022, my most spectacular find was a large red-and-white striped fish with blue paddle fins and armed with aggressive spikes on its back: the red lionfish.

Unfortunately, the lionfish is no more a native to the Bonaire reef than I was. It hails from the faraway western Pacific, brought by ship, or escaped from an aquarium, to devastate the indigenous fish of the West Indies. To compound this sense of a Caribbean undersea world-out-of-joint, on my next dive I passed a group of volunteers engaged in the tricky task of building an artificial reef to replace the hundreds of square miles of corals that have been lost to climate change. Against the backdrop of Bonaire’s remaining, resplendent reef wall, the manmade coral structure appeared pathetically tiny, like an underwater gym structure for preschoolers. The divers were scrubbing at the fake antlered corals with what appeared to be toothbrushes.

Nature tourists know the feeling only too well. We experience our twenty-first century world as a split screen. On one side Earth’s still beautiful wilderness, accessible in patches – like the reef at Bonaire. On the other, our anxious sense that even these apparently untouched wonders are in fact manmade, and have changed radically in the space of a few generations. Pioneer environmentalist Aldo Leopold called it living “in a world of wounds.” For me, it has been a salve to those wounds to spend the past five years immersed in the experiences of a band of Victorian ocean explorers – travelling the world aboard HMS Challenger in the years 1872-76 – who were not burdened by our present-day consciousness of ecological loss.

Though perhaps they should have been. The Caribbean Sea the Challengers sailed across was certainly not ours. The magnificent reef systems they saw and studied in detail for the first time – dominated by so-called elkhorn and staghorn corals – are literally decimated: 90% gone. But even for these Victorian explorers, the Caribbean marine ecosystem was hardly pristine. For two hundred years prior to their visit in the 1870s, the slave plantations of Jamaica had subsisted on the meat of the green turtle, reducing turtle numbers from the tens of millions to a mere remnant. The celebrated manatees, too, were barely clinging to survival, while the indigenous monk seal had already been driven to outright extinction. Such is the dubious legacy of centuries of colonialism, overfishing and, more recently, ocean pollution: a global Anthropocene Sea depleted of its fish, charismatic mammals, and glorious reefs.

But to focus solely on extinction and endangered marine life is to miss a more dynamic picture of the twenty-first oceans and their relationship to humans. A more subtle, but no less consequential anthropogenic impact on marine life is how our vast global fishing fleet acts as a Darwinian engineer of selection and drives fish evolution – at an often breath-taking accelerated rate. By targeting certain profitable species – anchovies, tuna, mackerel, herring, shrimp – and trawling their breeding grounds to the exclusion of others, the $150 billion fishing industry drives changes both in the size, shape, and behavior of those species themselves, and in the entire community structure of the ecosystems supporting them.

A stunning example of human-driven fish evolution is the Chilean hake (Merluccius gayi), a stock commercial product of the largest fishery in the world located in the eastern Pacific Ocean. Approaching the harbor at Valparaiso in December, 1875, the scientists aboard HMS Challenger observed how the cold waters from the polar south rose up to meet them, turning the ocean surface from lifeless blue to a teeming green. This was the Humboldt Current, the southern hemisphere’s mighty counterpart to the Gulf Stream. Hake and mackerel filled the Challenger’s nets, which nature reserved for the diet of whales and sea lions, but which modern-day supermarkets sell by the truckload as packaged fish fillets.

Since 2000, however, the Chilean hake has mostly disappeared from the shelves, its population brought to the brink of collapse from indiscriminate overfishing. Climate change has also played a role in the Chilean hake’s decline. The warming of surface waters over the last 50 years means a more stratified, sluggish ocean, with reduced oxygen transfer between cold and warm layers. For the bottom-dwelling hake, fewer zooplankton survive the journey through the unventilated water column to provide fodder.

The adaptations of M. gayi to these existential threats, however, have been nothing short of spectacular. The Chilean hake traditionally spawned in subsurface waters under the loom of the continental shelf, their larvae migrating toward shore. But hake eggs are now smaller and laid closer to the coast compared to just a few decades ago, while juveniles have taken to congregating in remote places to avoid cannibalizing by their elders. The modern hake mature to adulthood in months rather than years. With drastic changes in behavior and reproductive cycle come changes in appearance. The grilled hake you order this evening at a restaurant in Valparaiso might be the same species caught in Challenger’s trawl – but it is a very different fish. The average hake is now barely half the size of its Victorian forebear. Such is the reality of fish evolution in overtrawled seas in the age of climate change.

What’s at stake for us with a global ocean in evolutionary overdrive? Fish are among the most heavily traded food commodities on the planet. Annual growth in demand for fish products has doubled the rate of human population growth for the past half century, while per capita consumption has likewise doubled (tripling in the developing world). On a collision course with rising demand is a decades-long decline in the proportion of ocean-caught fish in the global human diet. More than half of the seafood consumed globally is now the product of aquaculture – fish farms – located mostly in Asia. But aquaculture is an industrial solution to an environmental problem, with all the attendant hazards of waste and toxic byproducts. Fish farms take up valuable area on both land and in sensitive coastal zones. The captive fish, crowded together, are pumped full of antibiotics, which leach into the surrounding seas and waterways along with uncounted tons of excrement. A fraction of farm fish inevitably escape, too, and contaminate wild populations with industrial diseases.

A promising, partial solution to our over-commitment to aquaculture, marine scientists say, is to repopulate wild fish stocks through a novel approach called “balanced harvesting.” Traditional fishery “management” involves a crude selective process whereby the most economically valuable fish are captured at their maximal size, with whatever else is brought up in the nets discarded as waste. The result is a fish population deprived of its most productive spawners and an entire food web deprived of its keystone species and vulnerable to collapse. Balanced harvesting, by contrast, mandates fishing as broadly as possible across the given species in an ecosystem, and across age ranges within a species, leaving “big and old” fish in peace. The golden metric for balanced harvesting is to have human-driven fish mortality approximate natural rates. Reduced selection pressure will then allow fish populations to rebound, maintain diversity at the community level, and halt the runaway evolutionary merry-go-round that has made the Chilean hake almost unrecognizable. The most important benefit? A return to wild fish abundance will mean less human reliance on aquaculture to meet the inexorable demand for fish protein as the global population crests 9 billion by the mid-century.

Balanced harvesting recognizes the human presence in the oceans but with a view to naturalizing us as a structurally benign predator within a well-functioning ecosystem. There’s a larger planetary dividend, too. The carbon emissions load of a kilogram of fish is a fraction of that for beef, pork, and poultry. The greater the ratio of fish in the human diet means less warming of the oceans, which means more fish – a virtuous, tantalizingly sustainable cycle. “Living in a world of wounds” doesn’t mean there aren’t potential cures. The invasive red lionfish, unfortunately, though tasty, is a wily character that will never be a viable commercial stock. But a more balanced, scientific approach to seafood harvesting across the board – in the spirit of HMS Challenger– will be a step to ensuring our own descendants continue to enjoy a life-giving relationship with the oceans, and an all-you-can-eat platter of its bounties. Only the platter will look a bit different: there’ll be a variety of shapes and sizes, and fish you’ve never seen before. As Aldo Leopold might have said, sustainable seafood – wilder food – demands an adventurous palate.

About the Author

Gillen D’Arcy Wood is the Robert W. Schaefer Professor of Liberal Arts and Sciences at the University of Illinois, Urbana-Champaign. He is the author of the award-winning Tambora: The Eruption That Changed the World and Land of Wondrous Cold: The Race to Discover Antarctica and Unlock the Secrets of Its Ice (both Princeton).