Lake Rotorua. (all year round season) is the biggest of a series of Lakes in this area, all of which offer the angler a variety of challenges, rewards and scenery. The mouth of the Ngongotaha Stream into Lake Rotorua is productive and popular, a boat to take you to lesser patronised spots is a distinct advantage.
Lake Okareka also has a year round season.
Lake Rotoiti , and the bush clad Blue and  Tarawera Lakes  have 1 Oct to 30 June seasons.
The Blue Lake is attractive and has some beach access but is also popular for other water sports which are not conducive to fishing. Whilst Lake Tarawera has minimal access it has clear, deep water which produces great fish. A boat is useful as wading into the Lake is a tricky business and there is a shallow shelf which suddenly plunges into very deep water.

Lake Taupo has a year round season. Rainbow and some brown trout, average size catch 3.5 to 5.5 pound. Lots of places to fish from the Lake shore, popular spots are at the mouths of the inflowing streams such as the Waitahanui on the western shore.
Other productive spots: Hinemaiaia, Waimarino, Waitahanui,  & Tongariro Rivers.
Lake Rotoaira south of Turangi, has a 1 Sept to 30 June season and is a bush clad, private Lake administered by the Rotoaira Trust, to which an additional licence fee is payable.
Lake Otamangakau, west of Turangi,  season 1 Oct to 30 June, has been known to produce trophy sized fish (up to 8 1/2 pound). Views of the Tongariro Volcano can be spectacular, with reflections in the Lake on a calm day (take your camera).

See also Nelson Lakes

The Maitai River is only 15 minutes from the centre of Nelson with good access from near the municipal golf links, but worth venturing further upstream the fish are relatively small at about one one pound but can be numerous.
The Wakapuka River is only 20 minutes from town  with good access .
The Motueka River is reputably one of the best brown trout rivers in the South Island with good fishing within easy distance of Highway 6, season is 01 Oct to 30 Apr

Only 10 minutes from town is Lake Kaniere whose stunning beauty almost compensates for the less than perfect record of producing good fish. There are brown and rainbow trout here but your most likely catch is a perch.
The rivers and streams are probably a better bet, the Styx, Kokotahi and Harris Creek  to name just a couple, also the larger rivers the Hokitika, Arahura and Taramakau.
Lake Mahinapua has also offered up some decent sized catches.  The lakes are year round and rivers mainly 01 Oct to 30 Apr.

The lakes around the Tekapo region are, in the main, part of the Hydro power scheme here and are well stocked with fish. The streams and also the Hydro Canals offer additional opportunities. Lake Ruataniwha and the canals are year round with other locations being seasonal.
Fish the mighty Waitaki River, the lifeblood of the Waitaki power scheme, for trout and for salmon which were first released here in 1901. The river can be subject to discoloration from glacial silt depending on weather conditions, season 01 Oct to 30 Sept. 

Canterbury has it's fair share of fishable waters. The Ashley, Waipara, Cam and Styx Rivers and of course the vast expanse of the Wamakariri all open 01 Oct to 30 Apr. 

The lakes of the high country are special places, with even the largest being dwarfed by the vastness of the landscape.
Some lakes are easily accessible from highway 73, such as Lyndon and Pearson, the latter having stocks of Macinaw trout. Whilst other are accessible only by tracks with a metal (loose stone) surface.  The major rivers run through deep beds of shingle which produces a braided effect and can make access to the main channels difficult and ever changing, subject to recent rainfall, at other times access is easy . The season in this area is first Saturday in November to 30 April.

The lakes of the Southern West Coast are known for producing good sized catches. Lake Paringa is open all year round, but access to this bush clad lake is difficult and a boat is almost essential. A row boat would also be helpful to reach the southern shore of Moeraki (season 01 Sept to 31 May.

Lake Wanaka has a year round season and certainly hold some good sized trout. Some beauties can be viewed from the jetty on the lakefront adjacent to the town, unfortunately this is a no fishing zone and I think these fish will grow to be very big and very old as long as they don't stray to far. 
The Matukituki River is in a very scenic valley with spectacular views of the peaks of Mount Aspiring National Park and has a season of 01 Nov to 31 May.

Lake Wakatipu is year round fishing, and the mouths of the Greenstone and Lochy Rivers (as well as the rivers themselves Greenstone from 01 Nov and Lochy from 01 Dec, to 31 May) are recommended spots. 
Lake Hayes is known for it's Brown trout of an unimpressive size.
Don't forget the Kawarau River  with a season of 01 October to 31 May is best fished at either end of this season so as to avoid the busy holiday period when the river is busy with Jet boats, rafts, and canoes. Not to mention the poor fish being regularly dive bombed by people throwing themselves off bridges tied to rubber ropes.

Lakes Te Anau and Manapouri have year round seasons but because of their bush clad nature are best negotiated with the assistance of a boat.
The Eglinton River has good road access for fishing during the season 01 November to 31 May,  the ease of access does make this a relatively popular spot but we're not talking big population base here!
The Mararoa River (01 Oct to 30 Apr) should prove worthwhile and is crossed by State Highway 94, down stream is Rainbow country whilst venturing into the upper reaches you are more likely to strike Browns.