Edit - that'll teach me for assuming that "black death" equals "cormorants"... Slight edit to post as a result...
For mink control - some angler-led initiatives (e.g. the Monnow Fisheries association) and Conservation/angling partnerships (e.g. Trent Rivers Trust) have put in place very effective mink control programmes of trapping and humane dispatch under licence.
A good insurance option would be to introduce brashy cover to act as "fish refuges" (same principle as the artificial refuges you get on stillwaters).
If you are sufficiently gutted to want to help the situation then give me an email on
p.gaskell8@googlemail.com and I'll help you set up a local branch of "Trout in the Town" so you can adopt and look after a section of the Irwell.
Wild Trout Trust.
Paul