Trout fishing the stonefly nymp

Trout fishing the stonefly nymp

Anglers tend to use small-sized nymphs, but Tony Orman argues that larger nymphs can be very efficient too – especially in the case of the Green Stonefly Nymph...

One morning on a Buller River tributary near Murchison, David and I came across a particular fish. The fishing had been hard and the trout easily spooked. We’d tried a variety of nymphs: the Pheasant Tail, Hare and Copper, and others, all in sizes 14 and 16. We had reasoned the low, clear stream condition warranted smaller flies.

When we spotted this fish, it was feeding in a rocky riffle. David had a go with a Pheasant Tail, then with other patterns. Surprisingly, the fish did not spook. Flummoxed, David quietly retreated, and downstream we sat on the grassy bank talking options. There were few left, having tried almost all of them that morning – except for the Green Stonefly.

“Whoa! That big? Look at the stream conditions, low and clear,” exclaimed David, and then added with a grin, “You’re crazy!”

“Yeah, funny, Bridget says that. And my probation officer, too!” I laughed in reply. “But seriously, we’ve tried everything else. So why not?”

So on went the size 8 Stonefly. First cast and the 2.5kg brown trout swung over to the nymph and nailed it.

THERE HAVE BEEN other instances where the Green Stonefly scored on fussy trout. I recall one evening high in the mountains on the upper Karamea where, in the twilight, two good fish avidly fed but wouldn’t take the usual-sized patterns. On went the Green Stonefly, and bang, bang, both fish fell to it – but their mistake wasn’t fatal: both were released.

Stoneflies are quite remarkable as far as aquatic insects and trout tucker go. In their excellent book The Trout Larder, Duncan Gray and Jens Zollhoefer relate that the stonefly family has over 100 species.

‘They generally prefer cool, well-aerated water with stony or gravelly substrate, and are intolerant of organic and thermal pollution.’

So expect stoneflies in wilderness type, clean, bouldery rivers. Why should such a big nymph be so appealing to a trout? The Trout Larder authors probably hit the nail on the head when they said, ‘Their large size makes them a potentially important part of the trout’s diet.’

Large? Yes, they are very large – up to 30mm in length (over an inch long in imperial terms). Consequently, just one of these impressive creatures is the equivalent to a meal consisting of several mayfly nymphs.

The pair identified stenoperla, or green stonefly, as particularly important in the trout’s diet. Stenpoerla may live up to three years in the water before emerging, crawling to the stream bank on rocks or vegetation. Often empty shucks (skins) of the stonefly nymph can be seen on streamside rocks. The large green stonefly is a predator, stalking and ambushing small mayfly nymphs.

The Trout Larder says the nymphs are awkward swimmers: ‘The best time to use a green stonefly imitation is often when an increase in river flow dislodges the larger individuals, exposing them to drift-feeding trout.”

For more than 40-plus years I’ve had this pattern at the ready, and have used it with success on wilderness-type rivers such as the upper Whakatane, the Ruakituri, the upper Buller, upper Wairau, Motueka and Wangapeka Rivers.

I’ve also discovered the Green Stonefly nymph is a dualpurpose nymph, imitating not only the important green stonefly natural, but also a damsel-fly nymph. One day on a Canterbury high country lake, the trout were homing in on hatching damselfly nymphs. I had no artificial damsel patterns, so tied on the Green Stonefly. Employing a slow, darting retrieve I hooked a good brown – and then, soon after, another fell to this great nymph’s robust charms. 

   This article is reproduced with permission of   
New Zealand Fishing News

December 2016 - By Tony Orman
Re-publishing elsewhere is prohibited

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