Search:

https://www.ecan.govt.nz/your-region/living-here/regional-parks/waimakariri-river-regional-park/hunting-and-shooting/

Different for every area obviously but you do have to dig deeper than DOC and...

Environment Canterbury managed the rivers I was on and it was in their rule book also noted on signs at the major access points

Yip most Canterbury rivers are shotguns only in game bird season I got in trouble for shooting feral cats with a rim fire . Being 20 at the time and prone to going off half cocked I made sure the...