More Migratory Mayhem

Dragonfly and damselfly nymphs are two of the biggest draws (or at least the biggest bugs) as far as aquatic insect migrations go in lakes. But if your preference is to fish streams and rivers, it is the stoneflies that cause a stir at this time of year with their migratory antics.

Like the Odonates, stoneflies crawl out to emerge and so the adults are not available to feeding trout until they return to the water to lay eggs (or get blown onto the water).  Despite this, stonefly hatches can provide some fantastic fishing both during a hatch and in the days leading up to a hatch.

Things that lurk in the dark (Pteronarcys californica adult)

As the time for emergence approaches, many stonefly nymphs will start to migrate from their preferred feeding habitats to near-shore areas where conditions favor a smooth transition to the terrestrial world. As they migrate they become more available to feeding trout; both as they crawl along the bottom, or enter the drift to surf into back-eddies and slicks. Trout will station themselves along edges near the shoreline to intercept anything that wiggles or crawls within range.

When hatches are heavy, shed exuvia can be found on many surfaces along a stream
(Pteronarcys californica exuvia)

With more trout feeding on these often larger nymphs, search images are formed and retained as the migrations progress to the actual act of emergence (often taking place after dark). Knowing what species are present in your local waters can be a big help in fly selection. A quick search of shoreline rocks, bushes, or bridge abutments can provide clues as to which species are active. Golden stonefly nymph imitations are generally a good choice and can simply be drifted along any shoreline edge or seam, or slowly worked along the bottom in the slack edge-water below a riffle.  These are big bugs that bring larger trout to the feeding trough, so even if the water is a little high and off-color, working the edges with a stonefly nymph is always worthwhile.

Golden stones are common on many western streams and rivers (Hesperoperla pacifica nymph)