The joys of fluff chucking.
Paul is right, clay pool is great, but if he ever wants to treat himself than the christchurch bridge pool is full of trout, a bit pricey but you dont need a Christchurch permit to fish it. You pay for the pool, punt etc and it allows two people to catch a lot of fish.
I have taken sea trout when they run at Sturt pond, a brackish bit of water behind the milford shingle bank, loads of fish there but they can be tough, mullet galore though. Dont cost anything though.
Royalty fishery, day permits in davis tackle or available on xchurch book. Good fishing and quite easy. I catch loads when after chub and barbel. The trout even eat a lump of luncheon meet so a fly there should do really well. Make sure he has a rod licence that covers game fishing though if hes on the river.