Why do crayfish never get identified

[charr113]

My friend is interested in observing all the crayfish species in Missouri, but almost 50% of his observations never get identified at a species level. He has tried all sorts of pictures, and even got a macro lens, but nothing works. Are there specific pictures identifiers need, or is it just that they are almost impossible to identify without a perfect specimen.

[loarie]

Dan_johnson has some great resources like this in his journal https://www.inaturalist.org/journal/dan_johnson/16497-how-to-photograph-crayfish-for-inaturalist

[zygy]

This website might be useful for anyone that wants to take a stab at IDing them: https://www.invertebratezoology.org/country_pages/state_pages/missouri.htm. Sorry I don’t have a good answer for your question though.

[AdamWargon]

Why do crayfish never get identified? Dan explained it here:

@dan_johnson

For crayfish, there are about 400 species in North America, a large percentage of which are observed on inaturalist, but only about 10 or 25 (depending on new or old criteria for CV training) have enough research-grade observations to be included in the CV, which means CV is going to be wrong for 97 or 93% of crayfish species. And often people seem to disagree with the top CV suggestions and pick one that they think looks more like their specimen, usually making the guess even less accurate.

[AdamWargon]

@charr113 Tell your friend that he can be the change that he wants to see in the world. He can use various resources to learn to ID crayfish. It’s a triple win:

• He’ll experience a lot of personal growth
• He’ll be making iNaturalist better for all users, by training the CV
• He’ll be contributing to habitat conservation and protection, because some crayfish species are endangered

[larry216]

I don’t know anything about identifying crayfish, but the most recent Observation of the Week is an interesting coincidence on this subject.

River Otter as Photo Assistant - Observation of the Week, 9/4/25

[AdamWargon]

If you like going down rabbit holes, then I encourage you to click on Larry’s link, above.

That “Observation of the Week” post links to another “Observation of the Week” post by Tony from 8.5 years ago, that got no comments.

And that post links to a video about a trip that Louisiana crayfish took around the world, that ended up back in Louisiana. It ties in European colonization of the USA, invasive species, and the rise of China. There’s a quote about pulling on a thread and unravelling the world; this is the crayfish version of that!

[AdamWargon]

@charr113

My friend is interested in observing all the crayfish species in Missouri

I think Southern Appalachia has the highest crayfish diversity and endemism in the world, but the Ozarks are a hotbed of crayfish diversity as well. Your friend can spend the rest of his life documenting crayfish, if he has the ambition!

[nickcarlson]

The one thing I get told whenever I request crayfish IDs is that I need a picture of their underside. I’m not sure what identifiers are looking for, but apparently that’s important

[AdamWargon]

@nickcarlson

I’m not sure what identifiers are looking for

@dan_johnson explained what identifiers are looking for in a couple of journal posts:

https://www.inaturalist.org/journal/dan_johnson/95366-guide-to-photographing-procambarus-simulans-and-p-curdi-for-identification

https://www.inaturalist.org/journal/dan_johnson/16497-how-to-photograph-crayfish-for-inaturalist

[Joeb]

@nickcarlson

I’m not sure what identifiers are looking for

Gonopods

[sethshively]

I think a big part of it is there just aren’t enough identifiers for them. I ID crawfish fairly regularly in Virginia/eastern US, there are a few other people who do occasionally for this area but not very regularly. Many of my own crawfish observations never get ID’ed despite showing all the identifiable features. I would help out with the Missouri observations, can take a look when I get the chance, but am not as familiar with the species in that area so idk how much help I could be.

It certainly doesn’t help the motivation of the few crawfish identifiers that the vast majority of observations don’t show identifiable features, as was mentioned earlier. While some species do require closeup shots of the gonopods (male reproductive organs), the majority can be identified with simply a clear shot of the dorsal view and claws combined with the location, however even this is lacking in most observations

[edanko]

You can take perfect photos and they can be IDable without a specimen and still not get identified, because there is a shortage of identifiers…

[DianaStuder]

@charr113

almost 50% of his observations never get identified

How is 50% = never ?

PS on behalf of the 130 who Never ID. Or the 3% of iNatters who provide 90% of all IDs.

https://www.researchgate.net/figure/Summaries-of-identification-effort-on-iNaturalist-Panels-a-and-b-summarize_fig1_372310054

[jasonhernandez74]

@sethshively

the majority can be identified with simply a clear shot of the dorsal view and claws combined with the location, however even this is lacking in most observations

Now I’m trying to imagine how observers could possibly leave out the most obvious angle. The only thing I can think of is that the chimney burrows are more often seen than the crayfish themselves.

[jnstuart]

@larry216

don’t know anything about identifying crayfish, but the most recent Observation of the Week is an interesting coincidence on this subject.

River Otter as Photo Assistant - Observation of the Week, 9/4/25

I appreciate you posting this as I missed it. To my knowledge the crayfish in the Rio Grande in NM are all non-native and Faxonius deanae is a fairly recent introduction from the Canadian River basin in NM, the type locality. When we reintroduced otters in the Rio Grande about 15 years ago — one of my projects! — a possible benefit was control of invasive crayfish. So this photo has special meaning to me.

[jasonhernandez74]

@DianaStuder

How is 50% = never ?

Just as it said: 50% never get identified. I suppose that, for clarity, the thread title could be rewritten as “Why do 50% of crayfish never get identified.” I can see how the title as written could be assumed to mean all crayfish.

[dan_johnson]

If your friend is interested enough to want to find all the species in Missouri, he should probably get the “Crayfishes of Missouri” book: https://www.amazon.com/crayfishes-Missouri-William-L-Pflieger/dp/188724705X/ref=sr_1_1?crid=264VY06X5U3LE&dib=eyJ2IjoiMSJ9.qNT4Fi5JEvesOl_gKTB2-Zdny5FLOWZSpYEIlBa5mGgKX5Ng7EOCO85jpdjtJZzedcnqlVlVbHqjIvjsuu1SVEaWL2viUdIvbKYF-pIIlw1wzOARp_c5JfwNMbY-MM0oOWia7G-DUnrB4234m1KJvg.V09frK_GN2i7HGvZmaBaiWA_koqNNkGTzxu9gsghgpQ&dib_tag=se&keywords=crayfish+of+missouri&qid=1759669079&sprefix=crayfish+of+mi%2Caps%2C129&sr=8-1 . The species should not be hard to ID for someone genuinely interested in learning.

The price is shown at $600, but they list other options for less than $10. That’s the way to go.

I’ve been involved in iNaturalist since its infancy. Back in the beginning I followed the entire United States. As time went by and the number of observations went up, I eventually mostly stopped IDing species from the eastern US. Then I stopped most of the western US and concentrated on Texas, where I have the most expertise, and occasionally look at the neighboring states. I still religiously ID anything IDable for Texas, but it has become quite an involved job with the huge number of observations. Texas has had 2,264 crayfish observations in the last year.