The fish market has become a focal point for a significant identity dilemma. Labels now provide comprehensive details about the source, catch method, and whether the fish is farmed or wild. While we can distinguish between farmed and wild salmon, the nuances of their differences or similarities challenge simplistic categorization. When an animal, such as salmon, is removed from its natural environment and bred over generations for human consumption, both the fish and our perception of it undergo transformation. Although both types are labeled as “salmon,” do they truly represent the same species? At what point does the label lose its meaning?

This identity crisis is ours to navigate, not that of the fish. To us, salmon symbolize the wild, undertaking arduous journeys through rivers and oceans, leaping waterfalls to spawn or facing predators like grizzly bears. The term "salmon" is likely derived from the Latin word “salire,” which means to leap. However, the contrast between a wild salmon leaping upstream and farmed salmon swimming in confined pens is stark. The majority of salmon available today do not leap or migrate.

We are now in control of salmon's evolution—some species have even been genetically modified to accelerate growth.

Currently, it is estimated that over 90% of the adult Atlantic salmon in existence are found within fish farms, with nearly all Atlantic salmon sold in U.S. markets originating from these facilities. The prevalence of farmed salmon and the dwindling numbers of wild populations are raising questions about species definitions and altering our connection to the natural world. In a 1998 study, conservation biologist Mart Gross proposed that a new species, Salmo domesticus, should be recognized.

“Domesticated salmon differ from wild salmon as much as dogs differ from wolves,” states Gross, who teaches at the University of Toronto. Like dogs, farmed salmon now rely on humans for their environment and sustenance, and we guide their evolution—including the use of genetic modifications.

While salmon are not the first species to experience such an identity shift due to human influence, the transition from wild to domesticated has occurred remarkably swiftly. This transformation is unfolding within a single human lifetime, reflecting the Anthropocene era, where the lines separating nature and human activity are increasingly blurred.

After the Pacific and Atlantic salmon diverged approximately 15 million years ago, following a cooling of the Arctic Ocean, they further evolved into distinct species—one in the Atlantic and six in the Pacific. Over time, these species diversified into numerous genetically unique populations, each adapted to specific rivers and migratory routes.

In the 1960s, significant evolutionary changes began as Norwegians started farming salmon in fjords, industrializing the process from roe to fillet. While fish farming was not new, domesticating a carnivorous, migratory species was unprecedented. Despite the ecological concerns, these farms established a stable supply of salmon for local communities and export.

This control allowed farmers to select for faster-growing, larger, and more docile fish, leading to a genetic divergence between farmed and wild salmon. Research indicates a “parallel evolution,” where farmed and wild salmon in regions like Canada and Norway have become genetically distinct after just five to seven generations of selective breeding. This rapid artificial selection is outpacing the domestication of traditional livestock.

Marianne E. Lien, an anthropologist at the University of Oslo, published a book titled Becoming Salmon: Aquaculture and the Domestication of a Fish, which examines the evolution of salmon farming. As salmon are bred for a more uniform, market-ready product, their historical adaptations to their native rivers and migration patterns are fading.

This loss is significant, as environmental factors can easily disrupt farmed populations. For example, in August 2005, a storm in central Norway released nearly half a million farmed salmon into the wild. These escaped fish can interbreed with remaining wild populations, propelling Atlantic salmon down a new evolutionary trajectory at an unprecedented rate.

Research has shown that hybrid offspring of farmed and wild salmon possess weaker genetic adaptations for survival in natural habitats. One study warned of a potential “extinction vortex” for vulnerable populations, as hybrids can reverse the genetic divergence that allowed salmon to thrive in their unique environments. Another study projected a decline in genetic differentiation among previously distinct salmon populations. “Today, salmon are differentiated based on the traits selected in farming,” says Lien.

As salmon farming expands globally, operations have appeared in locations such as Chile and New Zealand, introducing Atlantic salmon far from their native waters. A significant proportion of these fish now exists outside the Atlantic, and they rely entirely on human intervention for their habitat.

This situation represents a reversal of the past century of human-salmon interactions. The domestication of salmon began long before large-scale farming, as they adapted to coexist with expanding human populations, navigating obstacles like dams and coping with changing water conditions due to pollution and reduced water levels.

In the Pacific, hatcheries have emerged to “ranch” young salmon until they can be released to bolster dwindling wild stocks. While these initiatives have prompted changes, they are less dramatic than those seen in the Atlantic.

Historically, rivers like the Sacramento and San Joaquin brimmed with juvenile salmon migrating to the ocean, with distinct populations returning to spawn at different times. However, the construction of dams and water diversions for agriculture and urban growth has severely impacted these migrations, leading to declining populations. Hatcheries were established to support these fish and help preserve the fishing industry and ecological balance.

Yet, for Chinook salmon, hatcheries predominantly produce fall-run populations, and juvenile salmon often travel to the ocean via truck due to low delta water levels. “Now, there is little or no discernible genetic structure among populations. We’re producing a single type of hatchery fish released en masse,” explains Robin Waples, a senior scientist at the National Oceanic and Atmospheric Administration.

Similar to farmed Atlantic salmon, which originate from a limited number of Norwegian populations and have interbred with diverse wild species in places like Iceland and Canada, the distinctions that evolved over millennia in the Pacific are becoming less pronounced. New categories are now emerging based not on evolutionary history but on the degree of human involvement.

The current classification of Atlantic salmon includes various categories, with wild fish occupying just one. The other categories comprise domestic fish, escaped “feral” fish, and those introduced in non-native habitats. These classifications are crucial because they shape our understanding of the changes we have instigated. Lien argues that the distinction between what we consider acceptable (wild salmon) and what we deem unacceptable (escaped farmed fish) is inherently ambiguous.

“Fishermen operate under the assumption that escaped salmon are out of place. Yet, these distinctions are arbitrary,” she asserts, likening the classification of salmon to a color spectrum. “It’s challenging to pinpoint where ‘red’ becomes ‘brown,’ but we can acknowledge the difference. Our categorization of the world is always somewhat arbitrary.”

Even among biologists, the lines of distinction remain unclear. Genetics is one way to illustrate differences, but it is not the sole factor. There has never been a universally accepted definition to resolve the debate over species classification.

“What we teach in schools is the biological species concept, which simplifies matters for students: if two individuals cannot interbreed and produce viable offspring, they are considered different species,” explains Gross. However, he points out that this definition neglects asexual organisms, including certain fish and reptiles, and there are over 20 recognized methods for distinguishing species. “In truth, the concept of a species is an artificial construct devised by humans to organize the biological realm. These categories are not fixed,” Gross emphasizes.

There are instances of species that could interbreed successfully but do not encounter one another due to geographical separation. This is how Pacific and Atlantic salmon are believed to have initially diverged, isolated by the cold Arctic waters until interbreeding became impossible. Currently, farmed and wild Atlantic salmon inhabit separate environments—wild waters and regulated farms. “Farmed Atlantic salmon are evolving along a path toward becoming a new species,” Gross observes. “They may have already been considered a different species when I first wrote about this in 1998, as they inhabit a distinctly different habitat.”

Not all scientists are in agreement. “Domestication induces genetic alterations through selection, but it does not lead to the emergence of new species,” argues Michael Blouin, an evolutionary geneticist at Oregon State University. He contends that even domesticated livestock like pigs, chickens, and cows should not be classified as separate species, as they can still interbreed with their wild relatives. He asserts that salmon are “nowhere near that level of domestication.”

Nevertheless, it is evident that salmon have changed. These transformations extend beyond genetics and morphology; they encompass shifts in language and perception. Domestication has introduced a relativity that challenges the very essence of what defines a salmon. Future generations may recognize salmon primarily as the abundant fish raised in pens, rather than as creatures that have evolved to navigate vast distances through freshwater and saltwater, overcoming natural obstacles.

Gross considers domesticated salmon as part of the ongoing trajectory of human agricultural development that commenced 10,000 years ago. Today, this agricultural influence is extending to new species and impacting not only those in captivity but also those that remain, to varying extents, “wild.”

As our relationship with both domesticated and wild animals evolves, the lines between the two are becoming increasingly blurred, leading to a world where few species remain untouched by human influence. Gross predicts, “Eventually, there will be few wild species that are not altered by human intervention.”

Matthew Berger is a writer based in Portland. He has contributed to Bloomberg, Agence France-Presse, and Upworthy. Follow him on Twitter @matthewoberger.