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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

Custom Hatch Charts

Custom Hatch Charts

This tool is unlike any hatch chart you've ever seen: much better in some ways, worse in others.

Rather than providing the traditional graphics of emergence times, each chart work more like field guide to hatches for a specific time and place. You set the location (continental US/Canada) and time of year, and this hatch chart will show you many of the species you might encounter, with some of the most likely near the top. It shows many species normal hatch charts don't. It won't be as accurate about well-known hatches on specific rivers as a good local fly shop's hatch chart, but it can help with understanding obscure hatches or fishing destinations without local expert charts.

Generate custom hatch chart

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Benefits of these hatch charts

When treated as a starting point and not the final word, these hatch charts are uniquely useful.

  • They will show you many times more species than other hatch charts, including minor hatches that don't appear on most or any other charts.
  • They can show you some specific species producing hatches in your area, whereas regular hatch charts often just use common names referring to multiple species. That's good enough for tying up the right pattern most of the time, but if you're interested in bugs for bugs' sake—or you want to look up a specific hatch to learn more about its emergence behavior or life cycle—then species names can matter.
  • These hatch charts can help with tentative identification. For example, I have often identified an insect to genus after photographing it for this site. Lacking a good species key, I try to guess the species (or possible species) by looking at scientific distribution records for every species in the genus, cross-referencing those with my location, and further trying to find information on expected emergence times. It often takes 15–30 minutes. With this tool, it only takes a few seconds to find the likely possibilities.


Because these charts are based on public and scientific records, they vary in reliability and offer only spotty coverage of a species' real distribution, especially for adults. Many if not most records are for nymphs and larvae.

  • They sometimes exaggerate the importance of very common species (such as Hexagenia limbata), even in the wrong location or time of year, because there are some oddball public records in large samples.
  • They still don't include all the species you might find, because many of the rarer species might not have produced any records in the source databases for the location and time of year you're searching.
  • They aren't river-specific and don't incorporate things like local guide knowledge. The public records they're based on are too sparse to allow that level of detail. The calculations are state-wide, and sometimes the hatches in one part of a state with great climate variety (like California) can be very different from those in another part. Results also include insects collected from lakes and warmwater rivers, which can differ from trout streams in emergence timing and species composition.

How they work

These charts are created on-the-fly programmatically based on professional and amateur species occurrence records in public databases. They take into account the number of such records to hint at species abundance, the timing of adult collection records at similar latitudes, and the extent to which records for a species were recorded near the state or time-of-year of interest.

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