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Better Utilisation of Wild Fish Around Fish Farms

Salmonids Sustainability Education & academia +3 more

NORWAY - There is an abundance of wild fish around fish farms, but it is not permitted to fish within 100 m of fish farms. Scientists at Nofima and the Institute of Marine Research have studied how to utilise these fish better.

Lucy Towers thumbnail

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 100 m. Wild fish have a tendency to be attracted to physical installations in the sea, a so-called artificial reef effect.

In addition, one presumes 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 100 m of fish farms, the coastal fleet does not have access to this resource.

The ban on fishing within 100 m 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 maybe should be utilised. This should primarily benefit the coastal fleet because it is this fleet that would normally have fished in areas where fish farms are located.

Different understandings prevail also among fishermen concerning the effects of fish farms in the fjords. Some believe the abundance of wild fish 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. Such a fishery must involve both the fishermen and the fish farmers.

We know of coastal vessels that have caught their entire cod quota just outside the 100 m limit, says Project Manager Bjrn Steinar Sther.

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 the fishermen.

More saithe than cod

Saithe was the predominant species round the fish farm that was studied. 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 100 m 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 to the fish farm by the feed.

Fish pots well suited

The fish pots that were tested worked relatively well. The size of the fish pots had a clear effect, with the largest fish pots having 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.

Using fish pots near fish farms offers many advantages. 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.

The quality of the fish caught under the fish farm was studied over the course of a year. With just one exception in April a trained panel of sensory assessors identified a small discrepancy in smell and taste which they linked to salmon feed. In general the fish was of good quality as a result of the gentle capture and consequently there were no limitations on processing or sale. There is little, if any, effect on the fish from the aquaculture activity and the fish may, therefore, be sold live or as raw material for any type of processing.

This project is entrenched in the Norwegian Seafood Research Funds (FHF) research group for coastal zone research and the Action plan for fishery technology.