Paul that observation of the Trout at night rings true for us on the brook, I dont know if it was always thus or just something 've noticed in later seasons.
( excuse me if this goes on a bit , but i figure some my find it interesting)
i ve always been the type to want
"just one more cast'' and ended up lingering long past home time.
We don't have deep pools, though over the years i've been creating a few scour pools for adult habitat, which disturb the free wading of the brook to he chagrin of some of the anglers... but i have given them handy posts to pull out onto the bank and guide them back in... Im not a complete barsteward. Whether there is any form of Thermoclines in these pools I am yet to discover.
As the Summer reaches it height so does the reed canary grass along the banks, and then the heavy showers drive it down on the surface. By mid summer upto a third of the surface on each side of the stream is covered with a green matt.
This is a mixed blessing. For fishermen it can be a pain, less water, more snags, weird currents and drags. for the residents a porch away from the prying eyes from above, a passageway up and down stream, a larder above
AND I presume, less radiation down to the stream bed and thus less warming of the brook itself. For the predators: Otters, Gooseanders and Cormorants, a fabulous larder where the meals feel a bit safer and less flighty!
What i've noticed when wading along these stretches when the light has gone to gloom and that last fly change is beyond you, that I quite often see ahead a tilting and quaking of the reed grass on the surface and out in the stream comes a larger than normal trout that gets straight into hitting caddis on the surface. These are our 2+ year olds ( our trout only get to 4+ ). Unless its mayfly or grannom in early season we never encounter these unless fishing really late,and a head torch is now a regular part of the kit. For my annual scale sample survey of the trout population i need these bigger fish to get a full representation, so I end up in the deep gloom trying to get an accurate measurement and prize off some scale samples from some 42cm+ slab of trout muscle that really doesn't want to be part of the survey!
At the moment Im going down regularly to see how the redds are doing, in the past I ve seen fish on the redds from Oct 25th through to the first week of November. As yet no sign this year, I think the water is too warm still, by now we usually have had our first freezing Hoarfrost to turn the last of the trees and cars with frozen windscreens to scrape off in the mornings, last night was 13c here, thats crazy warm for November in England.
Ten years back i was at a habitat conference at the Natural History museum , there was a group of forward thinking scientists who had taken a stretch of river and noted the percentage of tree cover, and popped the instream thermometers in that i want for the brook (
https://www.omniinstruments.co.uk/tinyt ... ggers.html).
They then planted more trees along the banks and over the years looked at the in stream temp range compared with external patterns and predictive range based on that. I cant remember how much they had shaved off but it was enough to make us sit up and take notice!
if we can top it at 17c or18c for exceptional summer days instead of 20 or 21c that we've recorded, that's going to be a great respite. ( our top air temp last year was 40.5c, thats 6c higher than our previous peak).
12 years ago we had an 800m featureless straight dredged canal that was knee deep all the way. I put in 10 sets of flow deflectors ( brush wood bundles) and spent an hour or two pushing snapped of willow twigs into the banks. We now have wading from ankle deep to over your chest waders, and 30% tree cover and a wonderful little meandering brook between the banks.
Its not that hard to make the improvements needed to counter the changes taking place if the fishermen are willing to get a bit more involved.
Tangled:Priceless!
...that research you pointed my way was/is excellent thank you its printed off for a proper read, ( i seem to take info in better when read off old fashioned paper for some reason) and so many cross references to work through, that's going to keep me busy for a while. thankyou. thats the great thing about these forums.
sorry to go on....and on and on.
all best pom
makes you wonder about jungle life !!). 
I do Nothing everyday .
I hooked one once. That didn’t just spook the pool but the entire river.