Aquaculture for all

Study suggests that wild fish may not be harmed if they ingest salmon feed

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A short-term cod feeding trial indicates that the quality of wild fish around aquaculture sites is not harmed if they eat salmon pellets.

More work is being conducted to assess the impact of aquaculture on wild fish populations

© Nofima

Recreational and commercial fishermen in Norway have reported the presence of feed pellets in the stomachs of the fish they catch. It both looks and smells unappetising, and many believe that these fish are not fit for human consumption.

But do we really know if this diet affects fish fillets?

Limited knowledge about the problem

As part of the “Coexistence” project, in which Nofima acquires knowledge about how marine industries are able to positively coexist, scientists initially conducted a survey among Norwegians to find out what they think of so-called “pellet-coley” – coley that eat feed around fish farms.

Fishermen in northern Norway said that aquafeed pellets affect the appearance and finishing quality of wild fish

© Norcod

Most people did not know anything about this. Only men over the age of 60 from Northern Norway had an opinion on the issue – maybe because these are the people who have experienced catching pellet-coley. In a new survey, northern Norwegian fishermen said that especially the smell, texture and appearance of the fish are affected by a pellet diet.

Nothing wrong with fillet quality

In order to assess the quality, the scientists fed a small group of wild-caught cod with pellets over a period of five weeks before slaughter. They then assessed the fish using a modified quality index method (QIM), where the main focus was on smell, texture and appearance.

“We were unable to find many significant differences between wild fish that had eaten pellets and other wild fish”, says postdoctoral researcher Ragnhild Aven Svalheim.

“The fish had the same texture, smell and appearance as other fish, but the fillet gaping was different. Wild-caught fish fed with herring and prawns had more filet gaping than those that had eaten pellets, but those that had eaten pellets had more filet gaping than wild fish.”

The difference between the groups depended on how much food there was in the gastrointestinal system of the fish. The results suggest that it is not what the fish eats, but rather how much it eats that determines the quality.