River fish are indeed deemed to be 'ferae naturae' (or 'wild animals') and are not owned by anyone . . . . . even any club that may, or may not, have the rights to fish on a particular stretch and definitely not a riparian owner.
So, if the taking of fish right? No, of course not.
Is it indeed reprehensible? Absolutely it is, in most cases
Would most decent anglers ever take fish?
Well now that, as they say is the 64,000 dollar question . . . .
Regardless, does the "crime" warrant imprisonment, deportation or worse?
No, it doesn't!