Fishing is different down here. No snapper, though Kingfish come as far South as Banks Penninsula in the summer. 

From CHCH you can go out Motanau, Akaroa or Lyttelton. 3 hours North there's Kaikoura. I'd recommend a bigger boat: 5m would be a good minimum with a cuddy cabin. It's colder down South. Wet Coast you can get out from Milford, Jacksons bay or Hokitika over the bar. 

Species seem to be mainly sea perch of Kaikoura, blue cod up and down the coast, Trumpeter and some deep sea species if you can find them. 

Overall the fishing is better up North, but it is what it is. There's more to life than fishing.