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Photo: Open-net salmon farms in the Westfjords..

Extensive Hybridization Between Farmed and Wild Fish Stocks

A recent report from the Marine and Freshwater Research Institute indicates that hybridization between local fish stocks and farmed fish may be more extensive than previously thought.

The report, titled Hybridization between wild Icelandic salmon and farmed salmon of Norwegian origin, studied salmon fry from 89 rivers throughout Iceland, with a focus on rivers in proximity to aquaculture areas. A total of 6,348 salmon samples were analyzed.

Read More: More Fish Escape from Aquaculture Pens in Westfjords

To meet international demand for the popular fish, fish farming has become an increasingly lucrative industry in Iceland. In 2015, some 8,000 tonnes of salmon were farmed in coastal pens. By 2022, that number has risen to 45,000 tonnes.

Recent reports have also shown that significant numbers of the farmed fish, which are of a different stock than the wild Icelandic salmon, have escaped their pens. The regularity and size of these breaches have led to fears of disease, parasites, and hybridization. According to report, “hybridization of farmed salmon with wild populations can alter local genetic composition, lead to changes in life-history traits and possibly even population declines.”


The study identified samples attributed to hybridization from the years 2014 to 2019. A total of 133 first-generation hybrids (offspring of farmed and wild salmon) were identified in 17 rivers (2.1% of the samples, within 18% of the rivers). Older hybrids were found in 141 individuals in 26 rivers (2.2% of the samples, within 29% of the rivers).

Read More: Damning Report on Iceland’s Fish Farming Industry

First-generation hybrids were more common in the Westfjords than in the Eastfjords, which is consistent with salmon farming starting later in the Eastfjords and being less extensive.

Hybridization was generally detected within a distance of less than 50 km from the farming areas, but some hybrids were found as far as 250 km away.

See also: Environmental Associations Call for Ban on Marine Fish Farming

“This extensive study confirms the importance of further research. We need to examine the exchange of generations of hybrids, their extent, and the causes of the dispersion of older hybrids,” stated Guðni Guðbergsson, Freshwater and Salmon Farming Division Manager.

The report can be read here in its entirety.






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