Anyone going fishing, take extra caution in this weather regarding the welfare of fish.
Waters are suffering very low oxygen levels at the moment and after landing a hard fighting fish, take extra care when releasing back into the water. Carp will need to be held in the water to allow the fish to get enough oxygen through their gills to swim off strongly. Failure to care for fish will often see them go belly up and die. Also, if you are fishing for specimens, remember to use a unhooking mat, and make sure it has been dampened before putting a fish in to avoid scale damage. If you ain't got one, any decent tackle shop will gladly sell you one.
Barbel are vulnerable to not being treated properly, especially by inexperienced anglers.
After catching a barbel, return to the water as soon as possible in a fairly strong flowing current. Cradle the fish with one hand supporting it underneath between it's head and belly, other hand gently supporting it just Infront of its tail fin.. Point the Barbel upstream and hold it steady until it has got enough oxygen through its gills to be able to swim off by itself, this could take up to 10 minutes to ensure it swims of to fight another day . It will let you know when it's ready when it flaps its tail for freedom.
Also, if not fishing a match do you really need to use a keepnet? Releasing fish soon after being caught will help them recover, where as putting them in a keepnet in this heat will likely result in fish fatalities.