Salmon: Salmon farming: danger to its wild relatives

On the occasion of the World Climate Conference in Dubai, the International Union for Conservation of Nature (IUCN) presented a current version at the beginning of December Red list of endangered species. According to her, around 15,000 freshwater fish species are threatened, 17 percent of which are threatened by a lack of water in the rivers. Other causes include shifted seasons and rising sea levels that push salt water into river mouths, as well as a polluted environment.

The Atlantic salmon, among others, is considered potentially endangered (Salmo salar). The global population shrank by 23 percent between 2006 and 2020 alone. Salmon stocks have been endangered in Europe for a long time. The reasons are varied: On the one hand, more and more invasive species are spreading. These can be particularly dangerous for young fish – such as the humpback salmon that migrates to Northern Europe from the Pacific (Oncorhynchus gorbuscha). At the same time, the fish are finding fewer and fewer prey items.

Another reason has to do with the fact that Atlantic salmon are born in rivers and then migrate to the sea. But the young salmon’s journey to the spawning grounds on the foothills is becoming more difficult due to the construction of more and more dams for hydroelectric power plants.

In addition, the salmon louse (Lepeophtheirus salmonis), a crustacean that feeds on the skin and blood of fish, especially in farms, and now also wild salmon. Viruses and bacteria can also affect salmon.

Escaped from breeding

Last summer, 3,500 adult salmon escaped from an Arctic Fish farm in Patreksfjördur, Iceland. Individual specimens from salmon farms had already found their way into rivers before. But now that more and more Norwegian salmon farmers are expanding to Iceland, the outbreaks are reaching a new dimension. This is also due to the lack of controls: the networks should actually be inspected weekly. However, no inspections were carried out at the above-mentioned facility for three months before the holes were discovered. Norwegian harpoon fishermen are now hunting escaped farmed fish in the Isafjördur region and throughout the Westfjords. In this way, farmed salmon that had escaped from a farm into a river in a fjord more than 100 kilometers away could be recaptured.

Since the outbreak at Arctic Fish in the summer, 500 farmed salmon have officially been taken from various rivers. Environmentalists fear that if the salmon in the rivers mate with wild salmon, they will weaken their population. This creates mixed breeds that are less adapted to the environment and are less able to reproduce. This in turn threatens wild populations, which could even die as a result.

Not reliably sterile

The fishing industry hopes that this problem can be brought under control with some genetic engineering interventions. As the Munich-based non-governmental organization Testbiotech reports, an application for the experimental release of salmon using New Genetic Engineering (NGT) was submitted in Norway in April. In the fish, genes that are important for the development of the reproductive organs were switched off using the Crispr/Cas process.

The sterile salmon, which are also patent pending, are to be used in fish fattening in nets in the sea. The sterility is intended to prevent their spread in the environment. They can also supposedly be fattened longer than their conventionally produced counterparts.

The Norwegian Scientific Committee for Food and Environment (VKM) examined the application – and rejected it. Reason: There is a lack of evidence that all genetically modified animals are actually sterile. This is due to the lack of precision of new genetic engineering. In the Crispr salmon there are some differences in the changed genes between the individual animals. Because only some of the fish that come from the modified salmon have the desired characteristics, confusion can occur when selecting the animals for fattening.

It is also unclear how Crispr salmon behave in the environment. For example, they could compete with the juvenile fish of the natural populations that live in the rivers surrounding the fish farms. If they are not completely sterile, they could pass on the artificial genetic defects and thus weaken the natural populations. They could also be more susceptible to disease and thus contribute to the spread of dangerous pathogens in the affected regions. Therefore, a release is unlikely to happen soon.