When the first ghostly shadow appears from the depths you catch your breath. Then another and another fish casually ambles along, not more than a rod length from the bank. You cannot believe your luck, baits are lowered into the margins and you retire back into the undergrowth.

As the sun rises higher in the sky nothing has stirred, yet still the fish can be seen slowly swimming around. Frustrated you decide to wind in and take a walk around. A couple of swims along you can just make out a huge fish, one of the original uncaught stock laying quietly in the reeds. Yet, something is not right, the fish is not just laying quietly, it is unmoving. Reaching for a stick you gently prod it's flank. No response. Life drained from this specimen some time ago.

As you walk back to your pitch the reality begins to sink in. The fish don't normally show like this. You try to spook them, but they just carry on, as if in a trance, a feeling of dread begins to feel your body.

That angler was me, almost ten years ago now. The carp didn't last much longer though, within a month most of them were dead and now only a handful survive, hardly anybody fishes there any more. Now if this was a lone incident then it could probably be put down to bad luck, pollution, or perhaps toxic algae, but it isn't. Between 1996 and 1999 the same scenario was played out at 228 sites around the country, and the frightening thing is, they were just the mortalities that were reported. Disease carries a stigma, and often goes unreported to the Environment Agency.

Anyone with an interest in carp and carp fishing should be worried, very worried about this situation. In the background though, a small team of scientists from the Environment Agency, led by my good friend and keen carper Philip Bolton, along with his colleagues at the National Fish Diseases Unit, have been piecing together just what is happening to our carp populations.

Spring Carp Mortality Syndrome

Most of the carp mortalities reported in the last decade have been clustered around the Spring and early Summer, hence the name Spring Carp Mortality Syndrome, or SCMS for short, has been coined. As water temperatures rise in the Spring the carp appear lethargic around the margins of the fishery and die over a period of several weeks. Not all the fish will die. Generally, around forty percent of the carp are lost, although this figure can be much higher if you are unlucky.

The strange thing is, that apart from being dead, the carp often look to be in good health, externally. The only consistent damage that can be found on affected fish is damage to the gills. Each gill is made up of millions of tiny folds of skin called lamellae. The lamellae are only a few cells thick and allow the gills to bring the blood into very close contact with the surrounding water. Oxygen dissolves into the blood and waste products from the blood pass out into the water. Normally these lamellae form a neat structure, like a row of little columns.

Environment Agency scientists have often found fish infected with SCMS to have massive damage to their gill lamellae. In effect, it appears that the gills fuse together, reducing their ability to absorb life-giving oxygen. Although how this disease actually kills carp has yet to be fully unravelled, I have my own theory. Slow oxygen starvation, and the brain damage that follows, would certainly explain why the fish just appear to lose awareness of their surroundings before they die. Still, this is only a theory, as it has proven very difficult to follow the course of the disease in the laboratory.

Not all fish are killed by the disease. Many appear to be able to combat it and will suffer less severe damage. There is some evidence that the gills can recover from the onslaught of the disease and will eventually repair themselves.

A long way to go

At the present time there is still a long way to go before the full picture is known. Although all the evidence points towards a virus, the actual culprit of SCMS has yet to be isolated. This will be an important step in understanding how the disease manages to spread so rapidly, how it operates and eventually, how to control it's spread.

It's out there

There is still a huge amount of misunderstanding amongst anglers and fishery owners about the various types of carp disease. Many carp are infected by carp pox, a disease which causes blister like lumps on the body of the fish. Although disfiguring, this disease is rarely fatal.

The other misunderstanding comes from confusion with Spring Viraemia or Carp Virus. This is another real nasty virus, again most likely imported from mainland Europe. Apart from killing lots of fish Spring Viraemia has little in common with SCMS and has only been found in 4% of the fish examined from recent mortalities.

So far though we have only just seen the tip of the iceberg. There are more than one hundred coarse fish diseases that have been identified in Europe and not in the UK, so far. Some may even have a greater effect in the UK than SCMS, and we must do everything possible to protect our fish stocks from this threat.

What can you do?

Another factor consistent over a very high percentage of all reported cases of SCMS is the recent introduction of new stock fish. Whilst the stocked fish are unaffected the established stock are often badly hit by SCMS, often within weeks of going in. What is more, the stocked fish don't even have to be in direct contact, as several fisheries have been infected when a connected fishery has received new fish. Not all carp are affected though, so some form of immunity must exist in the carp population. This gives rise to the possibility of building immunity into farm reared carp in the future to give them a natural antidote to this terrible disease.

The good news for the angler is that the risk of spreading SCMS on wet nets can be controlled by drying of nets and the use of antiseptic dips as the disease cannot survive for long out of water. Whilst there is a theoretical risk from wet nets, the risk of spreading the disease from introduced fish is much higher. The responsibility lies at the door of fishery owners and fish dealers. Direct contact with infected stock seems to be the predominant route of infection. The answer is simple, don't stock carp into established carp fisheries. If you do need to stock carp get them from a reliable source and try to quarantine them. Where possible try to look for alternatives to stocking, such as rearing your own fish or spawning habitat enhancement.

The future

Despite having a good modus operandi for SCMS, investigators are still some way from identifying the culprit and so are unable to develop a reliable test for the disease. Overseas scientists, working on what appears to be a similar disease affecting koi, the ornamental varieties of carp, believe they may have recently isolated the virus responsible. This appears to be a herpes type virus, one of the most difficult to find using conventional techniques.

The symptoms of the koi herpes virus differ in one main respect. The koi virus operates at much higher temperatures than has been associated with the disease in the UK. This could mean that the UK disease is a variant of the koi virus. At the present time there is hope that some headway might be being made by overseas scientists. It is hoped that work will begin in the near future to examine new fish infected with SCMS for the tiny herpes virus particles. For the time being it appears that we will continue to lose our precious carp fishing heritage whilst irresponsible individuals seek to earn a fast buck.

The Environment Agency is continuing to monitor all apparent outbreaks of SCMS as part of it's routine investigation of fish mortalities. If you see dead or dying fish then you can do your bit by reporting it to the EA on 0800 807 060. A leaflet describing the ongoing SCMS project, it's findings and recommendations for minimising the spread of this disease is available free of charge by phoning 0845 7223344.