Seeing as foreign speakers are relying on this forum, then I'm going to be a stickler instead of a tickler
I'm not certain that 'lock' is used in English in this context. Isn't it 'lake'?
A lock, among other meanings, is a short section of a canal with gates and sluices at each end which can be opened or closed to change the water level, used for raising and lowering boats.
Well Col, to me these are magnificent fishes full stop! They are just thriving in the environment that is theirs and that they do not control. I Don like the fat cows from under the cages but your fit fishes feeding on the extra food such as sticklebacks I d fish for everyday (especially if reasonably far from the cages - like at least a couple of miles so let alone 10 miles away!!!).
In many rivers in France we have the opposite issue: the use of aggressive chemicals for farming has killed natural life in and around rivers resulting in less and smaller fishes: are these less wild because without humans they would be bigger and there would be more of them?
The coveted brown trouts in NZ are all unnatural, but I d fish for them everyday if I Could afford to...
The English inability to pronounce LOCH,Is not my problem,it just gives me hours of laughs.
The world would be a much poorer place if our colonial forbears had not taken trout ova with them.
I know it's not presently PC thinking to admit it, but I'm glad they did!
The brown trout as an invasive species is not something most of us consider...
Humans are invasive too. They literally walked from central Africa to every corner of the globe. So I don't put much stock in brown trout being 'invasive'. Trout are limited in their range by water temperature, unlike other truly invasive species which are unfettered.