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Atlantic salmon, the native salmon that used to inhabit the northern Atlantic Ocean, rivers and seas, is a species now represented by an impostor: farmed salmon. Also known as cultured salmon, farmed salmon comes from hatchery genetic stock and unlike its native ancestors, lacks wild genetic variation. The wild fish our ancestors ate is gone. What appears on our dinner plates is a substitute copy, a genetic dilution of a once mighty fish, the adaptive king of the sea and a significant food for coastal humans since prehistoric times.

Photo credit: North Atlantic Salmon Fund
Photo credit: North Atlantic Salmon Fund

The change in genetic stock has been happening for decades, as farmed salmon are released into native waters via restocking programs (in an attempt to reduce the negative impacts of overfishing of wild salmon) and also unintentionally as a consequence of faulty containment in sea net-cages. The resulting “swamping out” effect—farmed in, wild out—along with several other insidious factors, has driven native salmon to effective extinction.

Genetic Erosion

When I began to research the scientific literature on native Atlantic salmon, I was stunned to discover that this species (Salmo salar L.) is essentially extinct. How can this be possible? Is the fish before our eyes and on our platters not real? Yes, indeed it is, but the verified statistic is that 99.5 percent of all Atlantic salmon living today, whether farmed or fished from open ocean or rivers, is not what biologists call “wild type” and does not faithfully represent, in a genetic sense, the native fish that once broadly populated waters of our planet’s Holarctic zone, the ecological region that encompasses the majority of habitats found across the Earth’s northern continents.

The fish we eat today is not the fish that fed our ancestors or even the fish that fed our forebears of a century ago. Today’s salmon, because of the effects of a force called genetic erosion, is the diluted copy of a fish that once thrived on a wild genome, that tried and true set of original genes which, in the case of salmon, generated a fish capable of magnetic field navigation, survival in fresh and salt water and geochemical detection of spawning micro-habitats.

Sockeye salmon preparing to spawn near outlet of Lake Brooks. Each of these salmon may represent as many as 1,000 other salmon that died in the attempt to return and spawn. Salmon face death throughout every phase of their life. Photo credit: National Park Service
Sockeye salmon preparing to spawn near outlet of Lake Brooks. Each of these salmon may represent as many as 1,000 other salmon that died in the attempt to return and spawn. Salmon face death throughout every phase of their life. Photo credit: National Park Service

Genetic erosion, simply defined as the loss of genetic diversity over time, eliminates the potential of a species to adapt to new environments and leads to extinction. The swamping-out effect by farmed salmon has been one eroding genetic force working against wild salmon. We human predators have overfished, toxically farmed, illiterately stocked, dammed and blindly released, by millions, farmed and unfit Atlantic salmon fishes into the wild. The hatchery stock has bred with and overrun the native species, one that had been evolving for hundreds of thousands of years and which is now genetically eliminated, all in the quick human feeding frenzy of the last century.

In visual terms, the force of this steep genetic erosion has clear cut to an industrial hedge and burned to the biological bones, a body of irreplaceable, adaptive genetic material equivalent to a massive, old-growth forest, one which had stood for millennia over the entire Holarctic region of Earth and which is frankly not restorable. One could say that the old-growth forest of Atlantic salmon is dead.

This is not an easy tale to tell. The salmon, however, is an able storyteller, being a familiar and marvelous fish. Salmon is anadromous, a migrant from fresh water to salty sea, a fish who returns to its birth river to spawn in the family niche for the next generation, for the continuation of each clan, the many clans for each population and the many populations for each species.

Technically, the only way to explain why the salmon you think you are eating is extinct is through the lens of population and molecular genetics. Yet, the salmon is truly a salmon of knowledge and can tell its story in many ways, being a once highly diverse and differentiated, smartly pedigreed family of kin and clan. If you can follow maps and glaciations, rivers and open seas, then you can follow the clans of salmon and their ancestral family trees and the recent loss of their protective, genetic canopy.

Salmonid Evolution

The earliest salmon came from a diverse group of ocean vertebrates known as the ray-finned fishes and was part of a broad divergence of ocean fishes that adapted over eons to the cold, northern waters of the upper Northern Hemisphere, around the Arctic Circle. Early Atlantic and Pacific salmonid ancestors branched into separate ocean groups of early species types about 600,000 years ago.

Well before the coming of its most evolved predator, Homo sapiens sapiens, before the industrial degradation of the earth’s ecosystems, before and after the last retreat of the Last Glacial Maximum, salmon prospered, undisturbed and free to navigate the seas and inland rivers. The females raked their redds (spawning nests), the males attended, their black-eyed eggs developed. They grew into spotted fry, then young parr (juveniles) camouflaged in lines matured to silver-scaled adults, who when ready put out to sea to amass body weight as they navigated the ocean using the Earth’s magnetic fields to guide them.

Photo credit: BPA.gov
Photo credit: BPA.gov

Consistently, the salmon returned upriver to breed again, homing back to their place of ancestry, their birth location, not only to pass down the best surviving, evolutionary genetic lines, but the unique adaptive differences of their clan, which allowed them to detect, recall and locate that singular family place as being their own. Innumerable salmon clans eventually earmarked to all of the available niches within the species’ final broad biogeographical distribution.

On their way, during their travels, over time and in prehistory, salmon differentiated. Individuals of each clan began to accumulate small genetic differences by random chance, breeding and keeping those differences unto themselves and their families. Salmon clans became unique within their family’s geographic niche because they spawned among their own. The clans grew and multiplied, each clan at its own location, spreading and creating more clans, larger and more diverse populations, accumulating more of those familial differences.

Clan-genetic differentiation can now be measured by DNA fingerprinting, has been shown to correlate to geographical breeding location and, most importantly, became locally adaptive. Salmon evolved to cull the identity by smell of their home waters in the elegant genetic processes of gene co-adaptation and where the salmon bred was where the salmon was most fit. Dynasties of ecological fitness, each clan best suited to its own specific breeding location, certainly emerged.

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