Wild saithe that eat excess feed from fishfarms are larger and fatter than saithe that do not eat salmon feed and of generally good quality. Photo: Helge Skodvin/Nofima

Project Year 2016

Coastal coexistence

 Seafood industry  

Can fisheries and the aquaculture industry share space along the coast?

Aquaculture and coastal fisheries are two major industries whose needs and interests sometimes conflict, especially when it comes to the effects of salmon farming on cod spawning and saithe eating excess feed from salmon pens.

However, new research has found that the quality of saithe that eat salmon feed is not necessarily inferior

“It is well documented that wild fish that eat excess feed grow bigger and fatter, and the quality of most of the saithe we have examined is good,” says senior scientist Bjørn-Steinar Sæther.

Positive environmental effect

Attracting wild fish to fish farms may actually be positive since they can eat much of the surplus feed before it reaches the bottom, where it can have a negative effect on the benthic fauna.

However, scientists do not have enough accurate data on feed loss and how much of this saithe manage to eat to be able to gauge this effect. In addition, waste feed may lead to increases in local wild fish populations.

“Wild fish near fish farms often grow faster, as they eat energy- rich pellets. The increased energy reserves yield larger roe and more eggs – and thus may provide a basis for more offspring. We do not know enough about the quality of these eggs, but so far our studies have not found any negative effects,” says the scientist.

Little difference

What about the quality of the saithe that eat salmon feed? Some people say that these fish are inedible, and some fishermen have reported poor quality of fish caught near fish farms.

The scientists fished using nets and jigs near fish farms at different times of the year over a period of three years.

The results indicate that the quality of the fish they examined was generally good, although slightly inferior in the saithe that had eaten salmon feed.

“Our results do not support the claims that all saithe that eat salmon feed are ruined,” says Bjørn-Steinar Sæther.

Norwegian Institute for Nature Research (NINA) and Institute of Marine Research

The Fishery and Aquaculture Industry Research Fund (FHF)

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