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Farmed cod spreads outside cages

It has been claimed that escaped, farmed cod has poor survival in the wilderness. Now new, extensive experiments show that escaped cod manages well outside the cages. Scientist Knut E. Jørstad doesn't see any barriers keeping farmed cod from interbreeding with the wild populations.  

By Marie Hauge

Knut E. Jørstad at The Institute of Marin Research says it is only a matter of time before the first hybrids are found.

- It is hard to imagine how the two populations can be kept apart in the wilderness, he says.

Side by side

Experiments carried out in Heimarkspollen in Austevoll in Western Norway have already shown that mature, farmed cod spawn in the net pen. The result is viable cod larvae that mix with wild offspring. The experiment also confirms that eggs and larvae from the net pen spread to adjacent areas. In the years to come the scientists will learn what happens when wild and farmed cod mature side by side.  

Vulnerable coastal cod

Stocks of wild cod are in decline all along the coast of Norway. These stocks are particularly vulnerable to genetic impacts from farmed cod, Jørstad points out.

The scientists keep a close eye on the farmed cod population in the Heimarkspollen. In 2010 they will know for sure if genetic interaction with wild stocks has occured. If so happens the viability of the hybrids and how the genetic interaction affects the wild stocks are topics to be further examined.

- The farming of cod represents a challenge with regards to potential interactions. We need to learn more about the risk of permanent, genetic changes in the wild populations, says Jørstad.