kyle.

There are a number of things that contribute to a favorable spawn.

Sufficient adult fish to do so.

1. water temperature, ideally around 50 f, lower than that you will have a delay period. As a rule in ideal conditions about 4 to 5 weeks before the eggs hatch.
2. high levels of oxygenated water at least 6 to 7 DO-PM
3. Low water is not overall a problem so long as the above is consistant over the redds.

That being the case, in that river the effective spawn will be closer to the springs.

Over and above that. Such things as high flood water stages and pollution will of course likely demise the success that year.
I doubt that the effects of angling pressure and loss of formed redds from wading is too much of a problem.

So far as l am aware of that river is not subjected to pollution as such either.

The practice of removing brood stock from a water and then in house incubating the eggs to return back to the river indigenous stock was first practised by the river keepers on the famous chalk streams of the south in the UK, and still is in some circumstances, as in some cases it is not allowed to introduce fish from any other source.
By this measn they are able to overcome the adverse effects of nature.

What would be interesting to establishon that river is growth rates and also long term survival

It may well be that the genetic strain that is there does not grow to large sizes, and that is not always a factor related to either water conditons, food base or both.

The survey does indicate a very high percentage of fish in the 8 to 12 ins size in the upper sections of the river.
Assume here fish in the second and may be third years of growth.

If you are aware of any data related to fish groth in that river l would like to know of that.

Fly fisheman for the best will in the world will also contribute to fish mortality, if that only amouns to 10 % for that river it is a loss of many fish.
I am not sure what the current regulations are so far as spin fishing is concerned. Do you have to use barbless hooks or not. If not then here again mortality will likely be high.

Couple that with wild life predation, be that otters or birds, the we can see why problems may exist.
Fish can as a rule deal with acceptable flood water, massive high water torrents are another matter.

I know that they did introduce as such special regulations, are they enforced as such, as l have never seen a wild life officer on that river.

I agree to introduce as such the regular stock fish Bow would not be a good idea.
As that strain as it now is, is special.

Let me know your thoughts here.

Davy