Diseased fish

Over the last few weeks a few diseased fish have been reported, all carrying the distinctive white fungal blotches. Once badly infected fish often move into the margins or slack water where they can hold station more easily and where they are much more visible. It is important to state that the white patches seen on all the dying fish reported are not UDN, rather they are caused by fungus, a secondary infection. The symptoms of UDN are quite different – lesions on the head, initially as grey patches on the skin on the top and sides of the head often developing into lesions or open wounds. Fish with UDN lesions can become infected with fungus but often the lesions heal up once the fish moves upriver. I have been trying to obtain samples from a fresh run fish with UDN head lesions all year with no success, the incidence appears to be much lower than observed last year and more akin to the normal background level.

Despite this over the last few weeks there has been an increase in  reports of fish either dying or already dead, all of which have carried extensive white patches of fungus.

A sea trout of about 4lb with advanced fungus infection. This sea trout was reported in mid May from a middle river beat.  There was still too much life in the fish for us to catch it but there is no recovery for a fish in this state. Fungus infection is usually secondary to some other initial damage, e.g predator damage, catch and release handling, UDN, etc but it is next to impossible to establish the primary problem once the fungus takes hold.

A sea trout of about 4lb with advanced fungus infection. This sea trout was reported in mid May from a lower river beat. There was still too much life in the fish for us to catch it but there is no recovery for a fish in this state. Fungus infection is usually secondary to some other initial damage, e.g. predator damage, catch and release handling, UDN, etc but it is next to impossible to establish the primary problem once the fungus takes hold. The sea trout pictured above had the top of its tail missing so it may well have had an encounter with a predator.

Fungal spores are everywhere, hence food left out in the kitchen soon develops mould from airborne fungal spores. It is the same in the river although the fungus spores are carried in the water, and any damaged fish is susceptible to fungal infection. This time of year always seems to be the worst for fungus but it usually clears up. It did last year following an increase in river levels and cooler water. We may well see an increase in affected fish in the next week or two but a change in conditions usually helps.

Similar fish have been reported from many rivers this year including the Dee, Tweed and Annan.

 

There are 3 comments for this article
  1. GRAHAM SALISBURY (SRG) at 12:59 pm

    Hello Brian, cut and pasted below is an extract from a well known Spey Ghillie, just wanted to have your thoughts on this view? ‘Those fishing above Craigellachie experienced their worst start to a season ever, something which could be attributed to the conditions but personally I’m not so sure, the Spey is a large river with no natural barrier to halt the progress of fish should they wish to ascend, and the fact that some fish were caught here suggests the main reason for the poor start was, quite simply, a lack of fish destined for the upper reaches coming into the river.’

    • Brian Shaw Author at 10:49 pm

      Dear Graham,

      I was aware of Ian’s blog, I view it regularly and it is always interesting to read Ian’s thoughts. It certainly was a slow start to the season, a feature of many north rivers this season including the Dee, as Ian alludes to further on the blog article which can be viewed here http://blog.speyonline.com/2013/05/a-summary-of-early-spring-fishing-of.html. As the spring progressed things seemed to improve with some middle and upper beats actually doing well with others struggling. Catch figures on other rivers are much more available than for the Spey and a look at FishDee will reveal that many of the upper beats had an uncharacteristically poor start to the season. I’m sure similar factors affected catches on the Dee as on the Spey.
      If the main point of your comment is the last sentence then that remains to be seen, not all upper river fish head straight up there.
      By the way what has this got to do with diseased fish?

      • GRAHAM SALISBURY SRG at 9:14 am

        Hello Brian, I think the concern is that our run is fragile enough without the added burden of a UDN outbreak for the second consecutive year, which can affect not only adults but the fry & parr as well. We are unable to influence the life cycle at sea, but we can protect and influence the stages in river to a greater degree. We need our nursery area, 11 million sq m operating at full capacity. Yours, Graham.

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