Ask any angler what they look for in a vehicle and you'll rarely hear about infotainment systems or ambient lighting. The conversation usually begins with a much simpler question: how much gear can it carry?

Ask a visiting angler about trout in New Zealand's Deep South and the priorities sort themselves out just as fast. Two of Southland's better-known trout waters sit a short drive apart, but they ask completely different things of you. One will quietly dismantle your confidence. The other, as local fly angler Pete Treacy put it with a twinkle in his eye, is rather more accommodating.

"Don't worry, chaps, the rainbow trout up the road are far more stupid."

He was right. Here's what we learned fishing both, and what we'd tell anyone flying in from overseas to do it properly.

Sort your licences before you sort your flies

This is the part that catches visitors out, and it's worth more to you than any fly selection.

You need a current New Zealand sports fishing licence to fish for trout anywhere in Southland. But some backcountry waters, including the Upper Oreti River, are Designated Waters. On those, a standard licence on its own is not enough. You need a qualifying base licence plus a separate Designated Waters day licence for each day you intend to fish, and overseas visitors are capped at a limited number of those days per region. Turning up without the second licence means you cannot legally fish, no matter how far you've flown.

Seasons vary water by water, too. Some southern lakes are open year-round while rivers and high-country waters open and close on set dates. Check the current Southland Fish & Game rule booklet for the specific water you want, not the region as a whole.

Two more things, both non-negotiable. Felt-soled wading boots are banned nationwide, and biosecurity officers will take them off you at the airport. And every time you move between waterways, you must Check, Clean, Dry your gear. More on why that matters below.

Start on water that gives you a chance

If you've never sight-fished for trout, do not begin on a hard river. Begin somewhere the fish are feeding and visible.

The Mavora Lakes gave us that. The drive in is half the pleasure: tussock gives way to thick beech forest, and the canopy closes over a narrow gravel road with sunlight and glimpses of water filtering through the leaves. If the scenery feels familiar, there's a reason. A minibus of visitors in full orc and wizard costume on the roadside confirmed we had arrived in Lord of the Rings country.

We set up on a grassy bank for lunch, and it would have been easy to spend an hour just looking at the reflections. Except we could see rainbows rising.

Compared with careful river work, this was wonderfully relaxed. We fished a hybrid approach of flies, spinners and softbaits, covering ground rather than inching along. On a light softbait set with a 10-gram golden spinner, the first rainbow announced itself quickly. Rainbow trout seem convinced that the fastest way out of trouble is to spend as much time as possible airborne, and this one cartwheeled across the surface throwing spray before charging off again. It didn't have the staying power of a kahawai, the saltwater fish most New Zealanders cut their teeth on, and before long it was in the net.

There was no secret to it. The fish were holding along the drop-off and rising regularly, so a decent cast towards the most recent surface disturbance kept working. Note that rules can differ between the two lakes, including whether you may fish from a boat.

Then go and get humbled

The Upper Oreti River is a different proposition entirely. It's known for large brown trout, and it has earned that reputation the hard way. On rivers where fish are plentiful, numbers forgive your mistakes. Here, nothing does.

The water is small and clear, and the trout are still almost invisible to a saltwater angler's eye. We watched former fishing guide Graham Watson and Treacy work upstream, scanning methodically, placing every footstep. It took 45 minutes before Watson whispered, "Yep, found one."

Seeing a brown trout is one thing. Putting a fly in front of it that it will actually eat is another. Hunkered low, Watson stalked closer to a fish holding against the far bank and made his first presentation. Ignored. He changed flies. Not fooled. The cat and mouse went on another 10 minutes before he winced.

"Argh, spooked it."

I lifted my head in time to see a broad-shouldered fish, maybe 6 pounds, drifting away downstream. We walked to the top of the beat and saw nothing more.

Three things to take from that. Look before you cast, because on this sort of water the hunting matters more than the casting. Treat one good fish as a full day. And accept the blank, because anglers who come here expecting numbers go home disappointed.

Access is managed by a beat system, with designated car parks. Parking at a ‘beat’ signals that it's taken. If a vehicle is already there, move on and find another. With neighbouring beats occupied the day we fished, we waved the white flag, or perhaps the brown one, and went to find Treacy's more cooperative rainbows.

Buy local knowledge, then give it a second session

We are not trout anglers by trade, which is why we asked locals to lead.

In Te Anau, with rain setting in, we called into Fiordland Frontier Supplies, where Shane traded intel for purchases. We stood casting in the rain at the edge of Lake Manapouri on his advice and got nothing. Maybe Shane had fleeced us.

The next morning, we gave his other recommendation, the mouth of the Upukerora River, a fair go. Third cast, the 7-gram black and gold Toby he'd sold us got whacked. The fish won its freedom before the net, but Shane was fully absolved.

The lesson for visitors: local advice is almost always sound, and one fishless session proves nothing. Conditions move fish. Give the tip a second window before you doubt it.

The driving is part of the fishing

Most of the good water down here sits at the end of gravel, often beyond phone coverage. That shapes what you need.

Capacity comes first. Rod tubes, tackle bags, camera cases, chilly bins and dry bags all went into a Ford Ranger Stormtrak and a Ford Everest Wildtrak, the Ranger taking the bulkier gear, and nobody travelled with a tackle bag on their lap. Access comes second: reaching the Upukerora mouth involved stream crossings, which is worth knowing before you book a two-wheel-drive hire car. By the end, the metallic grey Everest had changed colour entirely with dust, while the Stormtrak's mint green somehow still looked respectable.

Then there's the cold. Once the sun drops behind the ranges, the temperature goes with it, quickly, whatever the forecast said at lunchtime. Layers, and a vehicle with heated seats, are not indulgences here.

Leave it the way you found it

Didymo is present in southern waterways, which is why Check, Clean, Dry is a legal obligation rather than a courtesy. Know the bag limit for the specific water you're on and respect the beat system even where it's only convention. Both exist for the same reason: so, the angler who arrives after you finds what you found.

Do that, and you've earned the last tradition. The Cardrona Hotel has welcomed travellers since 1863, which makes it a fitting place to finish a trip like this. Once we settled in, the fish grew steadily larger, the seas became slightly rougher, and individual contributions to the week became increasingly heroic with each retelling.

Such exaggerations are not lies, of course. They are simply the natural evolution of fishing stories.

Nick Jones is a writer at Fishing News