Photo: Lars-Åke Andersen

How to best look after your catch

Planning a fishing trip this summer? The Nofima researchers have some excellent advice for ensuring that your catch is of the best possible quality.

Contact person
Portrettbilde av Tatiana N Ageeva
Tatiana N Ageeva

Ph.D. Student
Phone: +47 77 62 92 15
tatiana.ageeva@nofima.no

Did you know?
  • Freshly caught cod which is kept at a temperature of ten degrees for a day before being chilled to zero degrees will have a shelf life that is four days shorter compared to cod which has been chilled immediately.
  • The reason why the fish fillet “shrinks” when you cook it just after it has been caught is that the fillet has not yet undergone rigor and is not experiencing any mechanical resistance from the skeleton. The shape of the fillet therefore becomes shorter and wider, as it is completely unique when fresh.

You should apply the same rules as the professionals if you want to maintain your catch as well as possible, whether you are planning a fishing trip in mountain lakes or rivers or a magical trip on the fjords during the summer holidays.

Gently remove the fish from the water, bleed it quickly, keep it cold and avoid blood collecting around the fish.

Researchers at Nofima have carried out a series of trials on fresh fish and documented what it takes to guarantee the highest quality. The work has been carried out on behalf of the fishing industry, in collaboration with the Norwegian Fishermen’s Sales Organisation and supported with funding from the Norwegian Seafood Research fund.

Here are some of the most important findings, which will also benefit amateur fishermen:

Cooling

If you are on a longer fishing trip and the weather is warm, you should consider how to keep the fish as cool as possible. It might be a good idea to bring a fish box or similar with cold water on board a boat for storing fish. Use a ladle and replace the water regularly to keep it cold.

Bleeding

A live fish on board a boat or on land will get stressed, and the longer it sits before being bled, the more blood will seep into the flesh. Researchers therefore recommend bleeding the fish and cooling it down to four degrees immediately after it has been brought on board the boat/on land to ensure the best quality flesh.

For reasons of fish welfare the fish should be anaesthetised/killed by a blow to the head before it is bled.

Bleeding out

Following bleeding, the fish should be left to bleed out in cold water for at least 30 minutes before being further chilled towards zero degrees. It is best to lay the fish straight onto ice as soon as it has bled out. But this option is rarely available to amateurs.

However, it is worth knowing that if the fish is surrounded in blood at temperatures of up to ten degrees for a long time after bleeding, it will have a detrimental affect on both smell and appearance. High temperatures will very quickly start the fish’s decomposition process.

Filleting

Avoid processing the fish while it is experiencing rigor, i.e. when it has stiffened up following death. Strong rigor results in the fish becoming very hard and stiff and taking on an arched shape. This can result in incorrect cutting. The muscle is then physically torn up and there is fillet gaping. In addition, the trimming of fillets from a fish in rigor is challenging since the muscle is very hard and it is difficult to remove pin bones.

If you are intending to fillet, it is recommended that you do so before or after rigor takes place. The period before the fish becomes stiff – the pre-rigor period – can vary in duration from shorter than two hours to over a day after death.

Other contributing factors include handling the fish after it has been caught, flesh temperature and species. Haddock is easily stressed, and rigor can quickly set in. The more gentle the handling of the fish before it is killed, and the quicker it is cooled down to four degrees – the longer it takes before rigor sets in and the weaker the rigor experienced by the fish. Rigor lifts eventually, but it takes time. A codfish may remain stiff for up to two or three days.

Cold storage

It can be difficult to taste the difference between fresh and frozen products from the same raw material if the fish has been handled optimally prior to freezing, bagged or packaged, quickly frozen and thawed correctly.

During thawing of fillets that have been frozen before the fish becomes stiff (pre-rigor), what is known as “thawing rigor” may occur if the fish has been stored in the freezer (at approximately -18oC) for less than a month.

Thawing rigor can be a challenge if the fillet is thawed too quickly at a high temperature.  This results in the fillet contracting, water loss and the muscle becoming less juicy. However, it can be very difficult to notice the difference between fillets that have been frozen pre-rigor and fillets that have been frozen down while in full rigor.

If you need to make a quick fish supper, you can remove the fillets from the freezer and thaw them under cold running water.

Salting

Do not salt the fish when freshly caught, wait until rigor sets in. Pre-rigor fillets rapidly enter a strong rigor when salted. The muscle becomes very hard and does not absorb salt as quickly as post-rigor fillets. This means that it is difficult to achieve even salt distribution and the desired salt level for the fillet during light salting.

During full salting, pre-rigor salted cod fillets can develop a very hard texture, which can result in up to ten per cent less yield after rehydration than rigor or post-rigor produced fillets. They may also develop a deeper yellow colour than fillets that have been salted post-rigor.

Stockfish

If you are planning to dry the fish, we recommend using the freshest possible raw material for stockfish that is produced gutted, with the head removed, but including the spine bone. Pre-rigor raw material will give a better colour and consistency to the end product than post-rigor fish.

With respect to Stockfish without the spine bone, be aware that any shrinkage can result in a ridged and cracked surface.

All that remains is to wish you a good haul for your fishing trip. If nothing else, have fun.

Have a great summer and good luck!

Seafood industry  

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