Epilogue

Amid the jumbled corals, sponges, and rocks of an Australian reef, something remarkable is taking place. There, a blackspot tuskfish (Choerodon schoenleinii) is eating cockles. In and of itself, this is not peculiar; fishes munch on shellfish all the time. But this tuskfish is particularly notable: it uses a tool to open its lunch.¹ After nabbing a cockle on the reef, the fish carries the robust shell in its mouth to a nearby rock shaped like an anvil. There, the industrious tuskfish slams the shell against the boulder, repeatedly, until it cracks open and the delectable bits are exposed. A pile of shells strewn around its base reveals that the anvil has been used many times. Improbably, this assiduous tuskfish has finned its way into the world of tool use, joining human beings, a few other primates, and a handful of clever birds in taking a great behavioral step forward. Several other fishes also have taken to wielding tools: yellowhead wrasse,² orange-dotted tuskfish,³ tripletail wrasse,⁴ and graphic tuskfish have all picked up the trick.⁵ Even the California sheephead, that lovable denizen of coastal kelp forests, has been known to dash sea urchins against boulders to crack them open.⁶

What these fishes have in common is progress, and perhaps a dose of curiosity. Somewhere in their dim ancestral past, a tuskfish must have gripped a particularly hardy cockle shell and wondered, “how shall I open this?” Another may have spied a large rock and thought, “what would happen if I bash this shell against that stone?” Now fishes may not have the literal power of speaking to themselves, but one tuskfish must have tried the technique, and presumably tried it quite a few more times before perfecting the trick. That animal discovered, through curiosity and ingenuity, how to resolve a dilemma and feed itself in a novel way. And the discovery spread, perhaps through observation and imitation, so that anvil use is now common among blackspot tuskfish. Like carpenters, blacksmiths, plumbers, and other noble tradespeople, these humble fish have managed to solve old problems by applying new tools.

One can remain alive long past the usual date of disintegration if one is unafraid of change, insatiable in intellectual curiosity, interested in big things, and happy in small ways.

—Edith Wharton, A Backward Glance

Fish, in their small ways, are endlessly surprising. They inhabit a world deeply unfamiliar to us, so their most basic adaptations seem novel, even entrancing. We are far more familiar with the adaptations of terrestrial wildlife. Giraffes use long necks to browse high vegetation. Porcupines rely on stiff spines to defend themselves. Parrots crack seeds with their heavy bills. But because the realm of fish is largely concealed from us, their behaviors, forms, and modifications provide a rich opportunity for discovery. The challenges they face are unique, as are the opportunities they enjoy. Seawater is dense, requiring brawn to push through, but it is buoyant and can support creatures who grow to immense proportions. Oceans are cold, sapping strength and slowing growth, but they can be fantastically productive. While much of the sea’s depths are too dark for vision, water transports chemical signals and sound communication across meters, miles, and longitudes. The upper layers of the ocean, seven-tenths of the planet bathed in sunlight, offer unparalleled possibilities for photosynthesis, but its bounty inevitably sinks to the bottom of the sea. On land, the equivalent would be if berries from every shrub floated slowly into the sky, where terrestrial animals could not reach them. The marine world poses unique challenges, and it is little wonder that fishes have evolved so many fascinating and creative responses.

On our underwater safari, we have toured many of these extraordinary adaptations. A blue-chinned parrotfish can transform from female to male. Billfish and tuna traverse thousands of miles to find sufficient food, and many species are warm-blooded to boost their muscle power and efficiency. Prey often hide in the dim and chilly depths, but swordfish and marlins can rely on heated eyeballs to improve their vision while hunting in the near-dark. Anchoveta reach astonishing abundance, when upwellings are strong, and have adopted complicated schooling patterns to defend against ravenous predators. On the other end of the size spectrum, giants like mantas and whale sharks eat the tiniest of foods, plankton, and rely on enormous bulk to sustain themselves between patches of richness. Sharks hit upon a successful formula millions of years ago and have thrived ever since. On coral reefs, diversity spawns diversity, thanks to the endless number of interactions between denizens, and thanks to the nutrient-accumulating power of corals and sponges, two unheralded animal groups on which the very existence of reefs is founded. In more temperate and polar seas, great productivity clashes with slow growth, gifting the planet with some of its most important food fishes, but also challenging fisheries to manage them cautiously and intelligently. Responses to the already novel environment of the ocean become truly bizarre in the extremes of the deep abyss, where light, pressure, chemistry, and energy combine to produce some of the strangest beings on the planet. And along coastlines, the immense opportunities presented by mangroves and kelp, as well as the vast freshwater resources of the continents, have prompted coastal and migratory fishes to hone their own unique adaptations: magnetic navigation, salt-tolerance, mouth-breathing, even precision archery.

The proverbial bull shark in the ocean’s exquisite china shop is us. Like it or not, people have acquired stewardship over our planet and its oceans, and we bear a responsibility for managing and mitigating our widespread and tangible impacts. Plastics are accumulating in the seas, and in fish tissues. Climate change is shifting ranges, migration routes, and timing of spawning. Acidification slows shell growth and threatens coral reefs. A cocktail of chemicals slips into the sea, elevating disease rates and endangering fish reproduction. Nutrient runoff triggers dead zones in coastal waters important to both fish and fishers. Bottom trawlers damage habitat, and factory-sized fishing vessels turn fishes into corporate profits. Overfishing, simply taking fishes from the sea faster than they can reproduce, threatens populations of many wild animals whose behaviors and adaptations inspire and amaze us.

But if we are unafraid of change, as Edith Wharton encourages, and if we accept the challenge of stewardship, we can improve our treatment of the oceans and build on progress already underway. New South Wales, Australia and the state of California have banned single-use plastic bags, to slow the flow of plastic into the sea. In 2022 the US Congress moved to bar all trade in shark fins.⁷ Seagrass beds in Tampa Bay, Florida, have recovered to lushness not seen since the 1950s.⁸ Consumer awareness, at restaurants and fish counters, is helping promote sustainable fisheries. Marine tourism is surging and generating much-needed revenue for coastal communities. And considerable progress has been made, around the world, in management of our fisheries.

A recent review of wild-capture fisheries, by environmental economist Christopher Costello and fisheries biologist Daniel Ovando, found cause for optimism.⁹ Many of the world’s most valuable fisheries, comprising a third of all fishes caught, are in good health thanks to intelligent management and strong governance. Their review also suggests that much of the damaging influence of climate change can be successfully mitigated by better monitoring and administration of fish harvests. The pair specifically highlight the value of adopting rights-based approaches like ITQs and conclude, “the future of fisheries can be bright with effective fishery management interventions.”

Augmenting the catches from wild-capture fisheries are the harvests from aquaculture. These operations have exploded in productivity, geographical range, variety of techniques, and diversity of farmed species. While this productivity helps offset the pressures placed by capture fisheries on wild fish populations, it also poses important questions. The assumption that aquaculture is meeting global demand for seafood should be challenged. “I think that if there was increasing demand for fish in the world, we should be seeing higher prices,” says salmon fishing captain Megan Corazza. “So I don’t really buy that, to be honest, if there’s a lot of demand we’d be getting more than thirty-five to forty cents a pound.”¹⁰ New York University scientist Jennifer Jacquet speaks more pointedly, avowing that “they’re not trying to feed people with aquaculture, they’re trying to make money.”¹¹ In this light, perhaps carnivores like salmon and tuna should be reared mostly by hatcheries to boost wild populations, while diners concentrate on tilapia and trout and perhaps add a few new items to their menu such as farmed mussels and leafy marine algae.

Marine protected areas continue to offer the best chance to conserve wild fishes and their habitats. Ambitious targets of protecting 30 percent of the oceans by 2030 have recently gained traction, with many countries already well on their way to meeting that goal. Once marine reserves are put into place, and patrolled effectively, sea life rebounds within their borders. The resiliency of the oceans, due in part to the immense diversity of fishes and their myriad interactions, allows them to recover with amazing speed once negative impacts are halted. These reserves offer unparalleled opportunities for people to plunge into a marine world filled with fascinating wildlife, curious behaviors, and astonishing adaptations. To actually see the ocean beneath the curtain of its dappled surface, to immerse oneself in this strange and extraordinary environment, is to gain an unforgettable appreciation of our responsibility for the seas.

Whether you eat fish or not, whether you are in the middle of America or in the middle of anywhere—the ocean touches your life.

—Rashid Sumaila, “A Conversation with Rashid Sumaila”

The oceans have withstood radical transformations and even planetwide extinction events, and they will withstand the admittedly clumsy first centuries of our stewardship. Fortunately we have the capacity to investigate new solutions, with curiosity and creativity, to cure our errors. We are capable of dreaming loftily and adopting bold reforms when pressed by an undeniable need to change. Curiosity and ingenuity have driven human cultural evolution. Ancient ancestors figured out how to walk upright, and to scour coastlines for nutritious marine foods. Others invented canoes and paddles and circumnavigated the Pacific Ocean. We have conceived boats and steam power, winches and purse seines, refrigerated containers, and aquaculture ponds. Each was devised to resolve a dilemma, and each was successful, to a point. Today we are tasked with devising a new solution to a new impasse, managing our planet’s oceans so they can provide blue foods, now and in the future, while continuing to sustain wild fish populations. Like the humble tuskfish, we will have to apply new tools to these problems. Mostly, though, what we need is to remember to enjoy the small things, the delicate intimacy between cleaner fish and groomed client, or the sonorous hooting of an amorous toadfish, and rejoice that our planet and its oceans can provide such delightful spectacles. So long as we truly care for the sea, the sea and its fishes will take care of us.