Sea Trout
Important Information when Night Fishing for Sea-Trout
Fishing in rivers stream and drains for Salmon and Migratory trout between the end of the first hour after sunset and the beginning of the last hour before sunrise shall be an offence unless the bait consists of a natural or artificial fly with each hook not exceeding 10mm diameter.
Which means that the treble hook you use must pass through a 10mm diameter hole.
This is an Environmental Agency byelaw for the Northern region which can be accessed on the following website.
http://www.environment-agency.gov.uk/static/documents/Leisure/short_byelaws_261059.pdf