Media: Salmon may disappear due to fish farming

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The researchers say the loss of genetic diversity in the Atlantic salmon population in Sweden could jeopardize the fish’s ability to adapt to climate change. And for this, and completely lead to the disappearance of the population.

According to The Guardian, fish farming could have been developed as a means to revitalize dwindling fish stocks, but this human decision has given rise to another problem: declining genetic diversity.

The study now shows that the genetic makeup of populations of Atlantic salmon from a century ago is likely genetically overly similar compared to the current populations of 13 Swedish rivers. This, according to the researchers, could jeopardize the ability of fish to adapt to climate change.

The researchers compared DNA obtained from 893 archival Baltic salmon flakes collected by fishermen and fishing biologists in Sweden in the 1920s with 787 modern samples. The researchers published in the journal Proceedings of the Royal Society B that of the 13 rivers under consideration, only human-raised salmon populations live.

There was very little industry in the area in the 1920s and 30s, but by the 50s and 60s the hydropower sector was flourishing. It was then that, as a mitigating measure, the mass fish farming, formally called stocking, began. Evidently, genetic changes began to occur at the same time as cultivation, said lead author Dr. Johan Ostergren of the Swedish University of Agricultural Sciences.

Stocking problems start at the very beginning: salmon selected in so-called hatcheries is generally the same – selected for rapid growth, but largely lacking in the special survival skills of wild populations. If farmed salmon break out of paddocks or move away from a designated body of water and end up mingling with wild species, they almost guarantee their offspring the worst case in the genetic lottery.

For example, if farmed salmon from river A enter river B, which is home to exclusively wild salmon, the genetic diversity from reproduction between the two species in river B would technically be increased. But overall, the species in the two rivers will become more genetically similar, which could reduce the salmon’s ability to adapt to environmental changes.

In fact, given that mixed offspring are likely to carry poorer genetics and are therefore less likely to survive, stocking may not even reverse the decline in salmon populations in the long run.

“All these decisions [выращивать рыбу] were adopted in the 1950s and 60s … but since then they have never been scientifically analyzed. Maybe it’s time to actually have a more scientific basis, ”said Estergren.

Carlos García de Leanis, director of the Center for Sustainable Aquatic Research at Swansea University, who was not involved in the study, said the latest study added merit to the argument that stocking is not a solution to salmon conservation and cannot compensate for the loss. or degraded habitats.

“This is another nail in the coffin of stocking, … a techno-arrogant approach to salmon conservation that simply removes the symptoms (less fish), not the causes (less water, less habitat, more fractured rivers) by simply releasing the fish. , “he added.

“This is a very serious study that complements the growing body of evidence that stocking is at best a waste of time and at worst an additional problem for the same populations it is trying to recover.”