Catching cod in cages has been found well comparable in efficiency to using nets, trials in Sweden have shown.
The program, whose sponsors include the Swedish Board of Fisheries, a government agency, and the national organisation for professional fishermen, is still ongoing, but results so far point to an average catch per cage of 3 kilos, the Board of Fisheries reports. It is possible for a fisherman to collect between 100-150 cages on a working day.
A fisher using traditional nets catches 360 kilos on an average day, according to log books, adds Sara Königson, a biologist with the Board of Fisheries.
The Board says it wants to encourage the use of both methods – especially in the small-scale, coastal fisheries it wants to promote – since they are selective and do much less harm to the environment than bottom trawling. Fishermen using nets have however encountered increasing problems with a growing seal population doing damage to the gear.
Baited with herring, the one-cubic metre cages are set out with some 50 metres between them. In order to reduce bycatches of small cod, three sizes of selection windows have been tested; the ideal having proved to be one with a mesh size of 45 millimetres, according to Sara Königson.
“With that mesh size, cod under 38 centimetres goes free, with no reduction in catches of grown cod”, she added.
“Besides, bycatches of sea birds and porpoises are minimal, and a great advantage with this method is that the fish is alive when the cages are emptied, guaranteeing perfect quality. And if the weather is bad, the fisherman can stay in port for a couple of days; the cages don’t have to be collected immediately.”
A commercial advantage could be that cod caught this way could be eco-labeled, commanding a higher price.
The next step in the program, according to the Board of Fisheries, will be to develop a material that makes the cages secure for seal: as it is now, seals can squeeze them smaller and thereby get at the fish in the cage.
The scientists are running ahead of the seals, however – it took the seals a full year to learn how to handle the test cages, doing more serious damage.