Blair is our recent regulation expert so hopefully he chimes in soon in CAPs and colorful writing.
I also have never been asked to provide photo ID. I am sure your friend got wrongfully stereo typed.
Personally I would say just pay the 100$ fine. For me the stress of dealing with court, having to take days off from work ect are just not worth it.
If not have a look though the act, I could not see anything about needing to have valid ID. However I am pretty sure you can have all your fishing gear seized if you cant produce a valid ID and you can be detained the police can be called and then you have to deal with them. You are also required to provide them with accurate details such as your address or you can be charge with obstruction of justice.
http://laws-lois.justice.gc.ca/eng/regulations/SOR-96-137/ British Columbia Sport Fishing Regulations
http://laws-lois.justice.gc.ca/eng/acts/f-14/ Fisheries Act
http://laws-lois.justice.gc.ca/eng/regulations/SOR-93-53/ Fishery (General) Regulations
Inspection
49 (1) Subject to subsection (2), for the purpose of ensuring compliance with this Act and the regulations, a fishery officer or fishery guardian may enter and inspect any place, including any premises, vessel or vehicle, in which the officer or guardian believes on reasonable grounds there is any work or undertaking or any fish or other thing in respect of which this Act or the regulations apply and may
(a) open any container that the officer or guardian believes on reasonable grounds contains any fish or other thing in respect of which this Act or the regulations apply;
(b) examine any fish or other thing that the officer or guardian finds and take samples of it;
(c) conduct any tests or analyses and take any measurements; and
(d) require any person to produce for examination or copying any records, books of account or other documents that the officer or guardian believes on reasonable grounds contain information that is relevant to the administration of this Act or the regulations.
Your Photo Id I would also say is relevant to enforcing part D
PS: i was writing this while Clarki posted, The thing is im pretty sure you can fight and win because the officer did not cite the correct part of the ACT. You had a valid fishing licence