By Kathleen McKeoghain
Surviving a Frozen World
We know that the ancient, wild Atlantic salmon faced and survived Holarctic glaciation, for their genes also left a fingerprint of their biological survival gear in their molecular patterns. Well studied in northern Europe, there likely existed one or more refugia under the Weichlesian glacial plates, bodies of fresh water in which the prehistoric salmon survived as the rest of its world froze over, unable to migrate to sea.
Isolated in its clans, separated by distance and geological formations, in different rivers, breeding with no outsiders and accumulating differences, the ever-adaptable wild salmon colonies were yet diverse enough to self-populate over long periods of time, being naturally fit and self-sustaining. Meanwhile, saltwater clans were successfully breeding in the ocean. As the glaciers remained, the separated salmon clans accumulated and passed on those unique fitness differences for best survival in their different environments.
Then the glacial ice retreated upon the warming Holocene, about 12,000 years ago. The oceans rose and fingered inland into fjords and rivers as glaciers melted and individuals from refuge salmon clans began to spread into fresh territory. Some pioneered the newly opened, post-glacial rivers, challenging distance and falls, spawning further upstream again and again, as the case may be, until all of the available rivers of the north Atlantic islands, eastern Russia, the Baltic Sea and their appurtenant inland flows were filled with unique, wild salmon, a literal natural spectrum of glorious natural diversity.
In the lands abutting the northeastern Atlantic Ocean, this distribution and range included every river in and out of the sea coasts from the north of Spain to the Arctic latitudes and in North America from the Connecticut River northward. Here lived and bred the “wild type” Atlantic salmon, adaptive king of the sea and the “leaper,” the muscled fish of power, grace and fortitude. Meanwhile, our own species experienced an upturn during the advent of agriculture, about 10,000 years ago and spread around the globe. As far as the wild salmon was concerned, all was kept in checks and balances until our epoch of genetic erosion, the superseding Anthropocene, which began c. 1950. Ours is an historic epoch physically characterized by the plastic geological layer now forming as a permanent record in the crust of human industrial ways.
The salmon has taken a fatal series of genetic blows. Its “old growth forest” was set on fire by a human feeding frenzy that began with overfishing and was fed by industrial aquaculture. The genetic erosion is shocking and steep.
Today, 99.5 percent of all native Atlantic salmon has disappeared from the wild. In Europe, Scandinavia and around the Baltic Sea, native indigenous salmon has vanished from the Russian rivers Neva and Narva, the Luleälven and Umeälven of Sweden, from the Odra and Wisla in Poland and the Vilia of Belarus. In fact, only 10 of the many rivers which empty into the Baltic arm of the northern Atlantic Ocean sustain wild salmon populations any longer and the wild Baltic salmon genome is the only one with natural resistance to the destructive Gyrodactulus salaris parasite.
Around the British Isles, in Ireland and across the pond to North America, wild salmon populations are extinct or endangered or threatened. The Kola Peninsula of Russia is known to be a current refuge for wild type Atlantic salmon, yet is also known to harbor military and radioactive waste at ecologically harmful levels. The grand Torneälven of Sweden, called Tornionjoki where it traverses Finland, is one of the last rivers to host wild Atlantic salmon in the world. (For more on the status of Atlantic salmon, see the International Union for Conservation of Nature Red List map. Researchers at the Swedish Agency for Marine and Water Management have produced a report on the Baltic extinctions. Anna Tonteri, a conservation geneticist at the University of Turku in Finland has written an excellent doctoral thesis about the population genetics of north European Atlantic salmon).
The Baltic salmon extinctions were largely enabled by human destruction of migration routes for spawning, upon the building and operation of hydroelectric dams. Further molecular DNA studies of the hatchery stock salmon from this exemplary sea have demonstrated a genetic “homogenization.” Stock salmon populations constitute more of a weak puree than a chunky soup, in terms of “population genetic structure,” another statistical measure of diversity. This is why—although the map above may demonstrate a wide range and lesser areas of extinction—the actual number of wild salmon living within the extant areas is quite small at around 0.5 percent. In other words, the orange areas showing extant salmon are overall 99.5 percent inhabited by farmed stock salmon.
We have learned to overlay DNA diversity upon geography and geologic history, in a relatively new field called landscape genomics. The important data is not just in the map or the numbers of fish, but in the genetic quality and the relationships of the individual salmon that comprise the families, clans and populations. An apparent abundance by numbers does not mean a population is healthy, self-sustaining and diverse.
In Ireland, the release of farmed salmon has not only caused genetic erosion, but has disrupted the capacity of wild populations to adapt to warmer waters. This is a problem for salmon across its geographical range for the obvious reason of climate change. Strong and well founded recommendations for saving the remaining wild salmon include cessation of stock salmon releases and re-establishment of native spawning grounds. The future effects of warming waters, however, are unknown and not hopeful.
I can tell you a similar story about the Pacific salmon, the Oncorhynchusspecies—the chum, coho, sockeye and Chinook salmon—which are also extinct or endangered or threatened and which are also genetically eroded. The destruction of the 10-million-a-year run of wild salmon on the Columbia River is unfortunately historic. The Pacific salmon had populated its portion of the Holarctic range simultaneously with the Atlantic salmon. Recent research has verified that Pacific hatchery stock salmon differs genetically from wild salmon and does so from the first generation of breeding. More than 700 genes, according to the data, were associated with “wound healing, immunity and metabolism.” (Scientists at Oregon State University recently conducted a study published in the journal Nature that shows there is DNA evidence that salmon hatcheries cause significant and rapid genetic changes). The fish are raised in overcrowded, concrete tanks, eat an artificial, supplemented diet and live in polluted water that is released into the environment whether farmed inland or off coast.
Genetic variation is the key to survival. With variation, if the environment changes, those individuals with the right variation in their genes will be most able to survive, to adapt and to regenerate a population. That is why it is important to sustain a lot of different, varied individuals in the population, in the clan, in the tribe. Genetic diversity for living organisms is the biological foundation for long term survival, for adaptation to environmental changes and is essential to species for sustaining fit populations for future generations. Genetic diversity is essential for all life on earth to survive climate changes.
The old-growth forest of Atlantic salmon was the entire set of all native salmon genes required for response and adaptation to new environments, the genetic set encompassing all salmon diversity, before the beginning of overfishing and the industrial era of H. sapiens sapiens. This forest of genetic diversity stood, so to speak, in wild swimming, individual, native salmon genomes (not laboratories!) and was acquired over millennia of biological and environmental changes by natural selection. The old-growth forest contained the wild genes of each fish, a reliable molecular network, co-adapted, set like jewels in a biological filigree, fitness genes in a pedigree of clans that salmon had naturally conserved among themselves, to sustain themselves and to protect their own kind from and for environmental changes and to adapt, to diverge and to explore new places in their niches of the living ecosystem of our planet. The old-growth forest was everything genetically needed for wild salmon survival.
Stock salmon cannot survive without human intervention. The overcrowded hatchery conditions in which it grows cause numerous fish body abnormalities and require nutritional supplementation to cover for shortfalls in bone development and other physiological problems.
Protect Whatever Remains
Human cultures rose around the salmon, which has fed and continues to feed a lot of people. In the wild, its orange flesh color comes from its consumption of shrimp and krill and the absorption of these carotenoids into its tissues. These natural pigments may actually have a protective effect for the salmon, as well as nutritional value for its consumers, humans and bears alike. Pellet-fed, farmed salmon must be supplemented to obtain its pink color.
Native, indigenous, wild Atlantic salmon, its distinguished clans and tribes, did not need human help to survive and yet we have lost the salmon to our anthropogenic ways, to overfishing, fish farming, dam construction, inbreeding, poor stock management and environmental degradation. And from these genetically eroded hills has been created a hatchery-dependent, diluted salmon, an inflexible, non-diverse and certainly not wild, genetic copy of salmon that we fish, farm, release and eat and even feed to our pets every day.
Spring Chinook salmon. Photo credit: Michael Humling / U.S. Fish & Wildlife Service
More than 99 percent of Atlantic salmon, Salmo salar L., live only as genetically eroded, hatchery stock fish today. That is a most sobering statistic considering the engineering of the Pacific Chinook salmon growth hormone into the Atlantic salmon genome (see my earlier article here). Whatever remnants still exist of our wild salmon populations must be protected without exception, especially given the potential introduction of a new, genetically engineered salmon to our frankly fragile food web.
Moreover, the pollution and operation of inland fish tanks is costly. At this point in the Anthropocene, conservation interests may want to rise up another step against the introduction of industrialized, non-native food species (call them what you will) into the only biosphere we have in which to live, until we are able to halt any further species genetic erosion. Salmon has been swimming upstream against the depleting force of “genetic erosion” for at least a century, a force that has claimed its wild genome, its clans and its tribes, its genetic diversity and which has nearly eliminated a once self-sustaining, powerful ocean species. Now, salmon cannot live without us.
Atlantic salmon is essentially extinct because we have demanded too much of this natural resource through over-consumption and environmental exploitation. The wild gene forest that once lived, the old trees, the towering antiquarians of genetic variation, are gone, lost in the fire of a rapid, wholesale, industrial Homo sapiens taking, consumed in an anthropocentric fire we could even see burning, when one looks at the timeline of scientific data.
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