If the Oreti is a sign of things to come then Didymo will ruin much of New Zealand's pristine trout fishing. I've not said much about the Oreti in the past; there's too many damned angler encounters already. It's certainly a world class water - or was. I drop into the Oreti and fish the top three sections every year once or twice. You walk 14-16K, see 40 fish, get half a dozen good shots and if they're on the fin, more. An average day is 2-3 fish but you're there to hit it right of course and do something miraculous.
It's windy here, so that can screw up your day and of course you're likely to run into other anglers which will completely ruin it. Well it does mine anyway. 4lb would be small. 10lb would be big.
Last year when we fished it during the back-end there was a rumour that Didymo had been detected. It's now everywhere, wall to wall, bank to bank, suffocating the streambed. I am shocked at just how quickly this stuff has taken over. The section I fished is now pretty much unfishable. I only had an hour because I hadn't intended ending up here, rather somewhere else. Spotted a trout in a backwater, which I hooked and lost, would have been around 5 I guess - the flies came back with Didymo - and I spooked a few others in a run (poor light).
Nymphing is near impossible, in fact even dryfly was picking up bits of Didymo both on the flies and the leader knots. It's truly an environmental disaster.
You MUST clean boots, socks, polyprops, flygear in Napisan/bleach/saltwater when moving between all waterways.