A large catch of cod that was caught in shallow water. (Photo: Ole Vegard Mosseng/Nofima)

How to better use wild fish near fish farms

NORWAY
Monday, October 15, 2012, 03:00 (GMT + 9)

There is an abundance of wild fish around fish farms, but it is not permitted to fish within 100m of those centres. Scientists at Nofima Mat, the Norwegian Institute of Food, Fisheries and Aquaculture Research, and the Institute of Marine Research have studied how to utilize these fish better.

Protection and access to food offer increased production

The studies showed that the amount of wild fish, both saithe and cod, was much higher right beside the sea cages than at a distance of 100m. Wild fish have a tendency to be attracted to physical installations in the sea.

In addition, it is presumed that wild fish can benefit from increased access to food either directly from the fish farms or by grazing on animals that exploit the increased access to food. As fishing is not permitted within 100m of fish farms, the coastal fleet does not have access to this resource.

Coastal fleet needs to consider

The ban on fishing within 100m of fish farms was introduced because of the large risk of damage to fish farms and fishing gear. The wild fish attracted to fish farms represent a resource that can and should be utilized.

A “win – win” situation

It is believed the abundance of wild fish in the fjords is reduced by establishing fish farms, while others claim the fish farms attract fish. The goal of this project was to study the basis for fishing wild fish around fish farms.

“We know of coastal vessels that have caught their entire cod quota just outside the 100m limit,” said Project Manager Bjørn Steinar Sæther.

The project, which involves scientists from both Nofima and the Institute of Marine Research, tested several types of fish pots, which will be able to provide a gentle live capture, better raw material quality and economic benefits for fishers.

The fish pot being slowly pulled to the surface. (Photo: Ole Vegard Mosseng/Nofima)

More saithe than cod

Saithe was the predominant species round the fish farm. Observations indicate that the saithe is attracted to fish farms primarily because of the access to feed. This is supported by the fact that more saithe were caught in the fish pots.

Saithe dominated the diet of big cod, and the cod caught near the sea cages were larger than those caught 100m from the cages. This indicates that the big cod are attracted to the fish farm to eat saithe. In all likelihood, smaller cod are to a higher degree attracted by the feed.

Fish pots well suited

The largest fish pots had the best catch. Video observations showed that movements in the fish pots scared away the saithe. Consequently, fish pots should be constructed in such a way as to restrict movement in the water current.

Fish pots are a relatively safe type of fishing gear with respect to damage to fish farms and other installations. As the fish are captured alive, it creates opportunities for controlled killing, bleeding and handling of the catch in an optimal manner, which provides raw material with whiter flesh and less variation in quality.

Source: Nofima

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