Re: trout vs carp
Definetly a water temp issue. Carp can live in a huge range of temps but they prefer much warmer water than trout. Carp wouldn't so much push the trout out as they would live where the trout can't. Probably not a good thing if your river temps are rising that much! As for catching them, my four rules are pretty basic.
1) know your forage
2) don't cast until you can see their head
3) you gotta make em move (to detect the take)
4) to catch more carp, cast at less (find feeding fish, ignore bad targets).
Good luck man!