This time of year nymphs are a big part of the diet of trout. Especially on rivers where smelt are not available or abundant. Most fresh water bait fish are not active first off in the spring so in many cases trout key in on nymphs first off in the spring. Like the Hellgramite, the Golden Stone is another big morsel.
This is the biggest stone fly that I have found in Nova Scotia at about an 1 1/4" long. Golden Stones need water with high oxygen content so high gradient streams and rivers have the greatest population. If you notice in the next picture that the gills on a stone are limited to where the legs and tails meet the body so the surface area for oxygen transfer is limited when compared to most mayfly nymphs and caddis fly larva that can tolerate slower less oxygenated water. The location of the gills and the tarsal claws (seen above) are the easiest way to differentiate a stonefly nymph from a mayfly nymph. A mayfly nymph's gills are located laterally along either side of the abdomen and they have a single tarsal claw on the end of each leg.
Although these nymphs are available all season it seems like trout pay more attention to them in the spring and then again as they start to hatch in mid June, but it could just be that I pay more attention to them at these times of year. These nymphs are crawlers and are not found up in the water column unless they are dislodged, so techniques that keep the presentation close to bottom and drifting freely in the current are your best bet.
I use a few patterns that work well for imitating golden stones, gold ribbed hares ear, Whitlock's fox squirrel nymph, terrible troths tied in light colours, but this one is a favorite.
Unlike their western cousins, eastern golden stones don't tend to hatch during the day so it is not uncommon to arrive at your local river in the morning to find the rocks covered with split shucks and wonder why you have never seen this hatch that is so legendary in the west.
Your best chance to present an adult imitation to rising trout will be in the evening when they return to the waters surface to lay eggs. The egg laying process is similar to that of dragonflies but without the grace, more like a belly flop. So trout have one of two choices, either take one out of the air or wait for one to get caught in the surface film. This is when those big stimulator patterns twitched through the surface film really shine.