This man-made lake covers 830ha. Set in wide, open Otago tussock 700m above sea level it offers exciting high country fishing for a good stock of wild brown trout. Due to its altitude and the open countryside it can be very exposed and bleak in adverse weather.
Lake Onslow is located east of Roxburgh, off SH8 south of Alexandra.
Bait fishing works well throughout the year but as the lake water is weedy and shallow, suspend baits from a float about 1 metre below the surface rather than using a sinker. Worms and grubs work well.
During the warmer months trout rise freely to take terrestrial insects that have landed on the lake. There can be excellent caddis and midge hatches and small midge and emerger sedge patterns fished just sub-surface work well. During the summer there can be very good fishing using cicada patterns. Fishing from the shore is best when there is a slight breeze rippling the water’s surface.
Trolling is the most popular method. As the lake is very shallow there is not much need to use weighted lead-core lines (and if using these use no more than 1 or 2 colours). Most anglers just use a good length of ordinary nylon.
Spinning is also very popular and to avoid catching the weeds that grow subsurface, don't let the lure sink too deep before retrieving..
The two most popular access routes are from Miller’s Flat and Roxburgh East, both off SH8. Both are good gravel roads but recommended for 4-wheel drive vehicles.
Although most of the access roads are private, they are usually available for public use by the owners if approached.
There is a boat ramp on the west side of the lake by a cluster of privately owned fishing huts.
Midge pupa and caddis emergers, Hare's Ear, and Damselfly
In spring and early summer use Royal Wulff, Coch-y-Bondhu, brown or green beetle imitations. In January and February, use cicada patterns. Later in the season use Black
Gnat and Peveril of the Peak. At dawn and dusk throughout the season, use Adams.
Wet flies /Streamers:
Water-boatman, Woolly Bugger, Hamill’s Killer, Mrs Simpson, Fuzzy Wuzzy.
Spinners: Black and gold Toby, green and gold Veltic, Mepps, silver and green Hexagon wobbler, and Jensen Insect.