[Rob Brownfield]

http://news.bbc.co.uk/1/hi/scotland/7347276.stm

So, the government are planning to kill all wild salmon in river systems if Gyrodactylus salaris  is discovered by introducing a poison into the water system that will kill the parasite and its hosts. They then would hope unaffected salmon would then re-populate the river.

I know its only a last chance plan, but I just cannot get my head around it. Any poison thats going to kill the Gyrodactylus salaris parasite and the salmon will also kill everything else in the river thus leaving it a barren wasteland. This will then have an impact on every other bird and mamal that relies on the river such as birds, otters etc.

Is this a truely effective way of dealing with the problem and can the killing off of an entire river be justified to protect a single species?

Any opinions greatly appreciated

[Graham Ritchie]

They can actually treat the river with Aluminium salts at a low dose rate. The aluminium is toxic to the GS parasite at a much lower level than the salmon or other fish (about a magnitude of 10). This solution has been tried on some Norwegian rivers infected with GS and has had some success.

[Rob Brownfield]

That is very interesting. Thank you for that. How does it affect the other invertibrates in the river system though? What about bioaccumulation within the fish?

Cheers

[Mike Barrio]

Hi folks

I know this will probably seem a daft idea ........ but mine usually are

What would happen if you simply netted a river off for a couple of years? Would the salmon that were in the river at the time die off ( as hosts ) and could this perhaps stop further "carriers" coming in to the system until a solution could be found at sea or by nature herself?

Trouble is, would salmon become "visitors" to the river again in the future if this was done?

Best wishes
Mike

[Rob Brownfield]

Interesting idea, but what about all the other fish that migrate or venture into fresh water..such as Mullet, Bass, Flounder, Eels, Shad, Smelt etc etc?

[Jim Eddie]

Mike

Not a bad idea in theory , but adult fish can cope with the parasite also trout and other fish species can be carriers but not be to badly affected. Its the smolts that tend to suffer.
The Norwegians poison the whole river system with Rotenone(SP) once the majority of the Salmon have gone to sea, but even killing everything has not eradicated GS. Also Norwegian rivers tend to be much shorter than ours , can you imagine the devestation in the Tay system for instance.
Basically if it ever get to the UK the Salmon are fecked 

http://www.marlab.ac.uk/FRS.Web/Delivery/display_standalone.aspx?contentid=861

 

Jim 

[Mike Barrio]

Interesting idea, but what about all the other fish that migrate or venture into fresh water..such as Mullet, Bass, Flounder, Eels, Shad, Smelt etc etc?

Good point Rob, I guess the netting could be done above the tidal zone so to speak?

I'm way out of my depth on this topic, but the idea seemed reasonable when it came to me

Best wishes
Mike

[Rob Brownfield]

I think it would be a nightmare Mile..imagine all the crap coming down the river in a spate...the nets would not last 5 minutes

[Mike Barrio]

Good point ....... I guess the best thing that we can do is to continue making sure that we clean & disinfect our own fishing tackle when going to and coming back from overseas and that we help to spread the word to other anglers

Best wishes
Mike

[Rob Brownfield]

I would advocate the use of a condom when using your tackle in unknown pools

Actually Mike, a question..when I went to the talk by the Dee Trust, they said they were worried about Rainbow fisheries as trout can carry GS. Are you ordered to carry out any precautions or is it left to the fishery owner to bear the brunt of any outbreak and how is the stock screened before stocking?? Does anyone give you any advice etc when stocking??

Down south you have to have a section 30 health certificate to move fish and I believe there is nothing like that up here??

Just how likely is it for a trout to carry GS?

So many questions...sorry...if you dont ask you dont learn

[Mike Barrio]

Hi Rob, my fish are "conceived" ( without the item that you advocate the use of  ) within 15 minutes drive from the loch ................................. 

Mike

[Magnus Angus]

"The Norwegians poison the whole river system with Rotenone(SP) once the majority of the Salmon have gone to sea, but even killing everything has not eradicated GS."

And there goes all non-migratory fish and a fair bit of invertebrate life.

GS can't survive in salt water. The known carriers are most other fish we get in most trout and salmon waters.

The scary bit on that BBC thing is the 'plan' for after killing the river - "It is hoped parasite-free fish would then repopulate affected rivers." From where? Salmon and sea trout at sea - ok - grayling, roach, perch, pike and all the wee guys. It reads to me like another of those non-intervention, nature will heal things. In Norway they take stock for re-seeding and re-population. Anyone know if any of the treated Norwegian rivers have re-opened?

My worry is that the plan may be the equivalent of the foot and mouth culls, a sanitary cordon, protecting uninfected rivers, which sacrifices the infected one(s). We may never fish them again in our lifetimes?

[Jim Eddie]

Apparently from the attached this drastic measure has been sucessful (if you can call it that) in 20 out of 26 rivers treated in this way.

http://www.marlab.ac.uk/Uploads/Documents/AAAH01Gyro.pdf

Personally I think it would be tragic if we ever had to resort to this method.

 

Jim

 

[Dave Gordon]

Gyrodactilus is present in all scottish waters at the moment, however the disaster strain Gyrodactilus Salaris is a baltic species that is not here yet!. It is 1mm long and born pregnant, so once it is here it will stay until every single one is killed. It has no effect on adult fish. It kills salmon parr by basically an allergic reaction, they cannot cope with the parasite and die.
The mechanism of infestation would be like this. An angler returns to Scotland with wet gear. He fishes with the gear and a GS parasite gets from the felt on the sole of his waders into the river. It is pregnant and infects a number of minnows, trout and parr, the infestation spreads and no one notices. Adult salmon return in huge numbers and spawn, we all think it has been a superb season. The following year the same happens. The next year the grilse run is very poor and the next year it does not come. The following year the 2,3,4 SW salmon do not return. Then we notice there are no parr in the river!
The trout, minnows, eels and the like are not effected but are effective hosts, and both these species and GS flourish. It can only be removed if every single fish is killed!
But GS is a weak parasite, and easily killed. It was described to me like this, anything that would kill a gold fish will kill it. So heating, freezing, drying and salt all kill it.
Interestingly, during research into it it was found it could not live in tanks with aluminium frames. It is very intolerant of aluminium salts. Research continues into this and hopefully a less drastic solution is possible. The Dee and Don are checked very regularly for GS by monitoring parr.
GS has been around forever and is easily killed. It cannot survive on ducks feet or any other natural mechanisim. It was spread in europe by fish farms and stocking but could easily be moved by anglers and canoeists. In Aberdeen Orvis, Somers and Aberdeen Fieldsports can all disinfect tackle quickly and effectively.

[Rob Brownfield]

Dave,
My reef tanks are very susceptable to poisoning from metals. Aluminium is a killer for most corals and virtually all the wee beasties that are a critical part of keeping the tanks "alive". This is one of the reasons why back in the 60's and 70's it was almost impossible to keep corals or use "natural" filtration..but these days its so easy..and it was all down to iron or aluminium frames.

Cass has done some work on this with her company and has looked into bioaccumulation in fish and inverts.