A number of fish this season have been found with red vents; whilst not as widespread as it was on Tweed a couple of years ago, all those who fish should familiarise themselves with signs of this worm - Anisakis, which manifests itself outwardly as 'red vent syndrome'. Anisakis is present in many species of fish, including Salmon.

           
Salmon with red vent - showing infected with the Anisakis worm                                                 Anisakis worms in a fish's gut


Whilst it is perfectly safe to continue to catch and handle fish with red vent syndrome, extra special care should be taken if the fish is going to be used for human consumption, or if any part is to be given to domestic pets such as cats and dogs, as the worm can live in humans and other animals, with very unpleasant results.

The following advice comes from the Food Standards Agency:

"There has been an increased prevalence of wild salmon in UK rivers infected with the parasite Anisakis.  We are therefore providing this Food Standards Agency (FSA) guidance for those anglers and netsmen who may want to eat their own catch or supply small quantities to local retail establishments or members of the general public.

 

Parasites in fish, particularly Anisakis, can, if ingested alive, cause serious health problems. Therefore the FSA recommends that anyone consuming wild salmon taken from UK rivers adheres to the following advice:

 

·           Visually inspect the wild salmon to detect and remove parasites. Those fish which remain obviously contaminated should not be consumed.

 

·           If wild salmon is to be eaten raw or almost raw it should be frozen in all parts for at least 24 hours, at a temperature of –20oC or colder.  This will ensure that any non-visible parasites or undetectable larvae of nematodes are destroyed. (NOTE: ordinary domestic deep freezes DO NOT freeze food to a low enough temperature to kill this worm.)

 

·           This freezing advice also extends to wild salmon that are to undergo a cold smoking process or to be eaten after marinating or salting i.e. as in Gravadlax.

 

·           Where wild salmon is to be hot smoked (internal temperature above 60oC), which is sufficient to kill any parasites present, then it is safe to eat without freezing first.

 

Where it is not possible to carry out adequate freezing it is advisable to cook the wild salmon.  A temperature of 70 oC for two minutes will kill any parasitic contamination present. As there is no infallible method of detecting and removing larvae, this advice is particularly relevant for pregnant women and elderly people, where ingestion of live parasites from fish could pose a serious health risk."


It should be noted that these worms are found in the guts of fish, so special attention should be paid to cleaning out the gut when preparing the fish.