We have seen them off the Wharf at Kaikoura but they didn’t seem to be as plentiful as in the sounds.
Despite hearing they are meant to be right around the coast of NZ I’ve hardly seen them or heard of them being caught in and about Chch, when I was a kid (13 to 14 years ago?) I remember fishing off a friends boat around Quail Island in Lyttleton Harbour there. I remember seeing a few piper swimming around the surface but that’s about as much as I’ve ever seen. Am not sure about Timaru, maybe others might have some further info?
As Shark Tale says if there seem to be alot of piper about just a ledger rig with small hooks seems to get them fine, and with any type of bait. Just lower it down 2 metres below the surface. Ultimately I think a float on the surface with about 1.5 – 2 meters of line underneath it would be ideal, small hooks and a small weight etc. Might be awkward to cast out but should work well.