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Shade nets serve no purpose

Several research projects over recent years have provided a significant insight into how the sun influences the temperature and quality of stockfish. This shows that shade nets are of no significance for the quality of the fish.

In 2011 Nofima carried out a large-scale trial involving hanging stockfish under shade nets on commission for the Fishery and Aquaculture Industry Research Fund (FHF). The fish was hung on drying racks on three dates: March 1, March 23 and April 14. On the same dates fish was also hung as a control on drying racks without shade nets.

Using shade nets over stockfish hanging on drying racks reduces the temperature in the fish, both the average temperature over the entire season and the temperature on sunny days. However, even though this temperature effect exists, the results point to the fact that the quality is unchanged in some areas, while it is worse in other areas. No reduction in important and typical quality defects in stockfish was found.

More negative than positive

It has been proven that the use of shade nets results in more negative effects on quality than positive effects. The discolouration on the skin, both grey and darker colour, was the same as anticipated after earlier experiences with stockfish not exposed to the sun.

“We had hoped that the shade nets could have reduced the formation of typical quality defects that can occur in stockfish, such as discolouration, larvae damage and mucoso (slimy/soft muscle). But we found no connection in this respect,” says Nofima Scientist Sjurdur Joensen.

Density an important factor

However, the hanging density when the stockfish is on the drying racks is important in relation to the temperature in the fish. A large distance gives warmth in the fish when there is a lot of sun, while fish hung close together creates shade for each other.

“But it’s important to remember that the fish should not be hung so densely that the draught round the fish is obstructed,” urge the scientists.

This work documents that traditional outdoor drying produces stockfish of better quality than with the use of protection from shade nets.

The trials were carried out at Brødrene Berg AS on the island of Værøy in southern Lofoten. The project was financed by the Fishery and Aquaculture Industry Research Fund (FHF), and was managed by Frank Jakobsen from FHF.

Report 2/2012 documents the results from the tests carried out in Værøy in 2011. (This report is in Norwegian language only.)

Shade nets are of no significance for the quality of the fish, research at Nofima shows. Photo: Sjurdur Joensen
Copyright: Nofima

Shade nets are of no significance for the quality of the fish, research at Nofima shows.