The leading theory at present is that this alarming-looking disease is an infestation by small Roundworm, Anisakis simplex and certainly, when this particular fish was opened, a cluster of roundworms was found inside the body cavity where the intestine meets the body wall to form the vent, as shown in the photographs below:
The Grilse with swollen, red vent
Opening up the fish, roundworms can be seen on the inside of the vent
Again, photo shows worms which appear to be living in the flesh of the fish
This worm is commonly found in wild fish and the advice is that, as always, fish should be properly cooked before eating.
The Fishery Research Services (FRS) of SEERAD have not yet formally identified this worm as the problem and are still investigating. As part of this investigation, FRS have asked that anyone catching a fish with a bleeding / bloody vent should report it to their local District Fishery Board with :-
1) A note on how many of the total number of fish they had caught had this symptom;
2) The date and place of capture of these fish;
3) A photograph of one or more of the vents;
4) Whether the affected fish were Grilse or Salmon, and what the total numbers of Grilse and Salmon were that they caught.
Many thanks to Mr. Paxton for donating his fish.
LOCAL REPORTS ON TWEED should be made by:
Contacting either the Tweed Foundation 01896 848271
Or the River Tweed Commission 01896 848294
Or by informing a Water Bailiff.
Contacting either the Tweed Foundation 01896 848271
Or the River Tweed Commission 01896 848294
Or by informing a Water Bailiff.