The short answer
- Chile has 63 stonefly species in 33 genera and 6 families, and 57% of them are endemic.
- Most belong to southern families shared with Australia and New Zealand; there are no salmonflies.
- Stoneflies were the most diverse insect group in the Aysén River basin survey: 19 taxa.
- Near Aysén, most species emerge between October and February; guides here report the peak in November and December.
- Klapopteryx kuscheli spends more than two years as a nymph, so it is trout food all season.
Why are there no salmonflies in Chile?
Stoneflies are an ancient order whose family tree splits along the old supercontinents: a southern suborder of Gondwanan origin and a northern one of Laurasian origin. Chile's national catalogue counts 63 species in 33 genera and 6 families, 57% of them endemic. Four of those families belong to the suborder Antarctoperlaria, of Gondwanan origin:
- Eustheniidae, with predatory nymphs, found only in Oceania and Chile.
- Diamphipnoidae, found only in South America.
- Austroperlidae, shared with Oceania, the family of Klapopteryx.
- Gripopterygidae, also shared with Oceania and one of the best represented families in Chile.
The other two, Perlidae and possibly Notonemouridae, are northern lineages that moved south. The salmonflies of the American West belong to a northern family that is not on Chile's list, so a Patagonian stonefly box looks different from a Montana one.
Which stoneflies live in the rivers we fish?
In January 2006, the Aysén River basin survey found 19 stonefly taxa, more than any other insect group. These are the nymph densities in four rivers we fish:
| River | Stonefly nymphs per m² | Most numerous |
|---|---|---|
| Mañihuales | 660 | Limnoperla jaffueli (630) |
| Emperador Guillermo | 486 | Limnoperla jaffueli (335) |
| Ñirehuao | 255 | Limnoperla jaffueli (135) |
| Simpson | 28 | Antarctoperla michaelseni (28) |
Nymphs per square meter (about 11 square feet) in riffle samples, January 2006. One survey and one visit per river. Source: Oyanedel et al. (2008), table II.
Limnoperla jaffueli and Antarctoperla michaelseni, both gripopterygids, were the workhorses: Limnoperla reached 630 nymphs per square meter in the Mañihuales, and Antarctoperla was the most widespread stonefly of the whole basin. The austroperlid Klapopteryx kuscheli ranges in Chile from 40° to 53°S; per square meter, it turned up at 40 in the Emperador Guillermo, alongside 63 of its relative K. armillata, and at 53 in the Ñirehuao, while the Mañihuales held 10 K. armillata.
When do stoneflies hatch?
The best emergence study near us comes from five forested mountain streams of the Futaleufú basin, on the Argentine side of the Andes at about 43°S, with several of the species recorded in the Aysén basin. Four gripopterygids completed one tightly synchronized generation a year, while Klapopteryx kuscheli needed more than two. Most species emerged in late spring and summer, from October to February: Notoperlopsis femina first, in mid-spring; Limnoperla jaffueli from November to January; Senzilloides panguipulli last, from January to April. One species emerged slightly later at the high-elevation stream, which the authors read as a sign that water temperature is an important control.
Guides who fish the Aysén Region report the stonefly peak in November and December, in step with that pattern and with the early part of our season.
How do trout eat them?
From the first summer to the last. In the Palena River, stoneflies were 27% to 33% of the prey items of fry and 12% to 19% of those of adult trout. Klapopteryx matters most by weight: its nymphs are shredders that feed on leaf litter, and in a forested Patagonian stream the shredders, led by Klapopteryx kuscheli and crane fly larvae, made up most of the biomass rainbow trout ate. A nymph that lives more than two years in the river is food that never has an off season. More on the whole menu in what trout eat in Chilean Patagonia.
Which flies cover them?
Flies are included in both of our programs; this is the stonefly logic. For the adults, guides in Aysén fish big foam attractors such as the Fat Albert and the Madam X in sizes 8 to 12, the kind of high-floating fly that also carries a dropper in hopper season. Under the surface, a dark weighted nymph fished through the riffles covers Klapopteryx. Mayflies and caddis complete the picture: mayflies and caddis.
Sources
- Vera, A. & Camousseight, A. (2006). Estado de conocimiento de los plecópteros de Chile [Current state of knowledge of Plecoptera of Chile]. Gayana 70(1): 57–64. Read the source
- Oyanedel, A., Valdovinos, C., Azócar, M., Moya, C., Mancilla, G., Pedreros, P. & Figueroa, R. (2008). Spatial distribution patterns of benthic macroinvertebrates in the Aysén River basin (Chilean Patagonia). Gayana 72(2): 241–257. Read the source
- Hollmann, M.E.T. & Miserendino, M.L. (2008). Life history and emergence patterns of stonefly species in mountain streams of the Futaleufú basin, Patagonia (Argentina). Annales de Limnologie 44(2): 135–144. Read the source
- Buria, L.M., Albariño, R.J., Modenutti, B.E. & Balseiro, E.G. (2009). Temporal variations in the diet of the exotic rainbow trout (Oncorhynchus mykiss) in an Andean-Patagonian canopied stream. Revista Chilena de Historia Natural 82: 3–15. Read the source
- Bravo, S., Whelan, K. & Silva, M.T. (2021). Assessment of trout populations inhabiting the Palena River, southern Chile. Latin American Journal of Aquatic Research 49(1): 29–39. Read the source
- Heinonen, T. Matching the hatch in Aysén, Patagonia. Kalakamu field guide (a guide's field observations, not a scientific study). Read the source
