Contrary to popular belief, the mackerel is not omnivorous. It prefers to feed on small fish and plankton. However, certain food sources can impair the quality of its meat. Photo: Jan Inge Haga © Nofima

Project Year 2018

What’s in the fish?

 Marketing research    Seafood industry  

Nofima scientists are looking for new ways to identify what fish have eaten using spectroscopy, saving the industry millions.

You are what you eat!
Some things fish eat degrade the quality of the meat, and in the worst case, a whole catch may go to waste. For example, mackerel often eat sea butterflies, whose shells are difficult to digest. Over time, the enzymes produced to digest the shells penetrate the intestinal wall and attack muscle tissue.
“The result is soggy, useless meat – and dissatisfied buyers. To ensure best quality, and avoid squandering scarce resources, fishermen need to be able to promptly identify type and amount of prey the fish they catch have ingested,” says Nofima scientist Geir Sogn-Grundvåg.

No objective method

He and his colleagues have analysed the mackerel auction market to find out whether buyers know what the fish they buy have eaten. Generally they do not.
“Fish are bid on unseen, so details about what the fish have eaten is important. Mackerel can contain a lot of small fish, which does not degrade the quality. Or they may have been feeding heavily on sea butterflies, also known as pteropods” says Sogn-Grundvåg.
Stomach content is currently only assessed on the basis of quantity, not type, and the industry has wanted a more objective method for some time.


Nofima scientists are testing new ways of finding out what a fish has ingested. Using spectroscopic imaging, they want to develop on-board photo boxes to verify type and amount of prey fish have been feeding on, prior to catching.
“The skipper simply takes a picture of a sample from the catch before the net is closed. If the fish have had a bad diet, the whole catch can be released unharmed, and the fishermen can leave the area and fish elsewhere,” explains Stein Harris Olsen. He believes an objective solution would benefit all parties.
“Fishermen will be better able to exploit their quotas, better quality mackerel will be brought to market, and scarce fish resources will not be wasted,” he says.

Capia AS

The Research Council of Norway

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