Notwithstanding the above, it should also be noted that if your mate, the one you are selling them to, is putting them in any waterbody in England and Wales, he needs a Section 30 from the EA to do it. Failure to gain the Section 30 for transferring fish and/or transferring fish without it is a criminal offence.
You yourself could be deemed as a fish dealer because money is changing hands and asked to justify why you have not requested/applied for said documentation and not surrendered 5% of the stock being sold/transferred for disease testing.
Further to this is the question of whether you are legally taking the fish from the water where they currently reside. The law here is quite clear, if those fish are being taken from an enclosed water (pond, lake, canal, reservoir), without the landowner's permission to take said fish, you are committing Theft under the Theft Act, again a criminal offence.
