There are some fantastic trout in Lake Arapuni, so I hope you have a good time. 

There are fish throughout the system but to my knowledge, the two best places to fish are right at the top of the lake, and down by the dam going out into the river.

I presume you aren't planning to try fly fishing, but want to try spinning from the shore or a boat?

So my advice is to use a spin set up similar to a soft bait rod and reel. 

I used to fish the lake a lot up below the Maraetai Dam where the water comes out of the turbines into Arapuni from the Maraetai lake upriver. It's more like a river than a lake at that point. Fast, dark water.

If you look carefully, you can see big schools of smelt finning in the water, and that's what the trout feed on to get big. 

My advice is to put a 1/4oz or even 1/2oz ball sinker running above a swivel, and have 2m of 3kg fluorocarbon trace down to a smelt fly. A size 6 silver Rabbit fly is a good choice, imitating a big lake smelt. If you can find one with prominent eyes, then that's the best. Pat Swift flies are very good, if you don't know someone who ties flies, or tie your own.

If you have braid on your reel, you'll need to tie a short leader to the braid before attaching the swivel.

On the western side of the river/lake, there's a carpark next to the hydro generators at Maraetai dam. Walk down the path to the river's edge, but make sure you are very cautious about the current. Maybe wear a life jacket, and have an adult with you. Don't fish alone. And don't leave valuables in your parents' car !!

What you do is cast up and across as far as you can, close the bail arm and keep a tight line as the sinker and fly sweep down. Follow the line with your rod tip. There are some big fish in the lake, including monster brownies, so be ready for a hit anywhere from opposite you to well below. 

When the sinker has swept down below you, wind in fast.

You'll snag the bottom a bit, but that's part of trout fishing, and you have to be down near the bottom where the fish are, hunting smelt. Take some spare nylon, sinkers and flies, so you can keep fishing.

In the outlet below the Arapuni Dam wall, you can fish the same drift method off the bridge over the road; or cast your fly rig off the dam into the lake, let everything sink for a while, and retrieve back towards you.

I guess that instead of a sinker and fly, you could try a soft bait on a jighead - something like a small minnow that looks like a small fish. But I think fly is more effective than lures (spinners, Tobys, etc) when trout are feeding on smelt that look like whitebait. And you'll need to see if scented lures are legal in the lake - I think they may not be, so you'll need to use non-scented ones. 

In the lake itself, if you have access to a boat or canoe you can troll, or cast over drop offs. Any stream mouth or deeper water outside stream beds is a prime spot to try.

And don't forget that unlike the sea, you need to get a licence to fish for trout.

Stay safe and enjoy yourself.

Tamure Kid