Eric R. Larson

YouTube video by Oregon Zoo Meet The Mazama Newt. And The People Fighting To Save It.

Happy Newt Year!

youtu.be/YkFhMYGAdCY?...

When I collected Okanagan Crayfish there in 2010, crayfish were hard to come by - a few individuals per multiple hours of diving nearshore. Abundances were higher in smaller lakes. Large Signal Crayfish active on the lake bed would really stand out, but it's of course a big lake. (2/2)

Yeah, I wonder about the status of these observations over the past five years - no obvious Signal Crayfish at Okanagan Lake on iNaturalist (only one nearby) but the divers of course may not be iNat users. Have people kept encountering big Signal Crayfish in the lake? (1/2)

Well, I shouldn't steal Caitlin's thunder, as the paper is in review. But it was interesting to compare across the many museum collections. A Procambarus zonangulus specimen did make our list of 20 largest crayfish documented in North America.

I fell short by ~10 mm CL to the two Bottlebrush species. But that 75 mm CL Signal looked like a lobster, and I would have guessed it was much larger than its measurement when I first saw it. (2/2)

Ah, 2020 - I missed the date. On 12 inch crayfish: Caitlin Bloomer is leading a paper on North America's biggest museum vouchered crayfish. I was confident I had the winner as a Signal at the Royal BC Museum, but (1/2)

I mean, there's a video here, but there's no scale to the video like the diver's hand or similar. The largest Signal Crayfish on record (~75 to 78 mm CL) look absolutely enormous in person, but 12 inches TL is crazy. It would be a record for both the Astacidae and Cambaridae to my knowledge.

... a diver seeing a big crayfish and not catching or measuring it is about as exciting a news story to me as someone claiming they saw Ogopogo. It's a fish story; get a specimen in-hand or it's nothing. (2/2)

Yeah, it's not clear to me from the article that anyone involved is aware of the Okanagan Crayfish as a species distinct to the Signal Crayfish or is just referring to Signal Crayfish in Lake Okanagan as Okanagan Signal Crayfish informally. But ... (1/2)

By the article, though, that isn't the crayfish claimed at 12 inches, which was seen by a diver but seemingly not collected. It's just an example of a recent big crayfish found dead in the lake (per the image caption). It would, however, be consistent with ~largest Signal at the Royal BC Museum

Last, on "put the ID of Okanagan vs Signal crays into some doubt" - I'm not sure how? We provide guidance on ID between the two species by morphometrics in the Zootaxa paper, and sequencing is cheap. The answer to whether they are Okanagan or Signal crayfish is an mtDNA barcode away. 6/6

Aschhoff said he's completed around 2,000 dives in various areas of Okanagan Lake over the last 14 years and has never seen a crayfish before. As the crustacean tend to live in rocky areas, they are usually found closer to shore.

At the news article, I'd worry about this quote. Extremely large crayfish at depth in the lake are a recent observation? Then that may be a new Signal Crayfish invasion, particularly as our Okanagan Crayfish specimens at the Royal BC Museum are generally smaller than Signals. 5/n

Because of their size, people stock Signal Crayfish for harvest (or sometimes as fish forage), including widely within western North America at Vancouver Island, Crater Lake, Lake Tahoe, southern Idaho (peerj.com/articles/5668/). I think many Signal populations are introduced. 4/n

Genome skimming supports two new crayfish species from the genus Pacifastacus Bott, 1950 (Decapoda: Astacidae) | Zootaxa

The Zootaxa paper spends both intro and discussion text on the risk of stocking Signal Crayfish over congeners, attributed, for example, as a cause of extinction and ESA listing for Pacifastacus species in California (www.mapress.com/zt/article/v...). 3/n

The signal crayfish is not a single species: cryptic diversity and invasions in the Pacific Northwest range of Pacifastacus leniusculus 1. We used historical sources, morphology-based taxonomy and mtDNA sequence data to address questions about the signal crayfish Pacifastacus leniusculus. These included evaluating unrecognised crypti...

I do not interpret Signal Crayfish as native to BC; they were introduced at the coast (doi.org/10.1111/j.13...), and I think the globally invasive Signal Crayfish was moved east of the Cascade Mountains, consistent w/Susie Adams' work in MT (doi.org/10.1002/wat2...). 2/n

I would say: I never collected Okanagan and Signal Crayfish in sympatry, from e.g. the same lake, including Lake Okanagan. I am aware of Signal Crayfish in the vicinity of Okanagan Crayfish, and include one of those populations (Loon Lake, WA) in the Zootaxa paper. 1/n

Looks like signal, I don't doubt they're around (certainly in the Columbia in WA & BC). Can't judge size from the image w/out scale. The largest crayfish of any species in any museum in North America is 86.6 mm carapace length (~7 inches total length); a specimen in hand would be interesting.

Three stream sites as columns over five sampling events as rows from fall (top) through mid-winter (bottom), taken from bridge crossings looking upstream. The stream in the left column is adjoined primarily by row crop fields with a wood lot in the distance. The stream in the middle column has an intact riparian buffer with leaves changing color at the top rows through absent in the bottom rows. The stream in the right column is the largest and is neighbored by dense riparian forest with a ridgeline visible in the middle distance.

This is another of our studies that I really value for getting us out to the same streams throughout the year, with a snapshot here of a few of our fall and winter sampling events.

Linear mixed model predictions for aquatic (blue solid) and terrestrial taxa richness (brown dotted) in response to (A) rainfall (in centimeters) and (B) water temperature (in degrees Celsius) with 95% CIs.

Do precipitation events have opposing effects on aquatic versus terrestrial environmental DNA (eDNA) recovered from streams and rivers? New from the lab at Ecological Applications: doi.org/10.1002/eap....

This is a little reassuring as an Illinois fan.

Image of river protection status in the United States

National assessment of river protection in the U.S.

Article: doi.org/10.1038/s418...
Policy Brief: doi.org/10.1038/s418...
Rivers Explorer: map.myriver.americanrivers.org

Collaboration b/t American Rivers, Conservation Science Partners, Univ WA @americanrivers.bsky.social

Thread 👇 | DM for PDF

Tarantula with XXL genitalia, 'death ball' sponge among cool species of 2025 | CBC News A spider with extraordinary genitalia, a carnivorous caterpillar that wears its prey's body parts, and a tiny opossum are among the cool new species described by science in 2025.

Excited that our newly described Okanagan Crayfish makes an appearance on the CBC's cool species of 2025 list: www.cbc.ca/news/science...

A black and white image of a signal crayfish (Pacifastacus leniusculus) seen from the side or lateral view with barnacles covering ~50% of its carapace.

Semi-related: this signal crayfish from G.C. Miller's 1960s thesis (The Taxonomy and Certain Biological Aspects of the Crayfish of Oregon and Washington), covered in barnacles out of the Columbia River estuary at Astoria.

bro you gotta molt

I'm recruiting a Ph.D. student for Fall 2026.

Interested in comparative studies and trait evolution in fishes?

Send me an email with a CV and research interests. Please take a look at my website (jcorush.github.io ) for more information about my research.

#hybridization #minnows #mudskippers

Black Doves

A red covered bridge over a river in winter with shallow snow on both banks and thin, clear ice covering most of the surface of the water

A red covered bridge seen from a river bank in early spring, with silver maple trees beginning to leaf out. The river is turbid, with sycamores visible on the far bank.

A red covered bridge seen from mid-channel of a turbid river in mid-summer, with forest on both banks

A red covered bridge in late fall with drifts of slush on its roof, seen from mid-channel of a wadeable river. Most trees have lost their leaves.

The Sangamon River of Illinois through the seasons. We visited this site every few weeks in 2025 to track changing stream communities with environmental DNA.

Two crayfish burrows seen from above or plan view

Two crayfish burrows seen from the side at an angle, where one burrow is about three times taller than its neighbor. The burrows are in surprisingly coarse or sandy substrate, with some fine, gray to orange pebble noticeable in the taller burrow.

New OA study led by Dr. Caitlin Bloomer of U. Illinois: can you predict good habitat for burrowing crayfish even if your model is trained on data from different burrowing crayfish species (doi.org/10.1111/fwb....)? Highly relevant to these hard-to-detect and identify animals.

A wadeable, second order stream in downstate Illinois that has recently had all riparian vegtation removed from one bank, where three researchers stand looking at the stream. The opposing bank retains a small block of forest in early spring, with invasive honeysuckle beginning to leaf out. A row crop field is visible in the middle distance below a blue sky with scattered clouds.

I know this result is a bit obvious, but I think it merits evidencing: if you remove all vegetation from miles of natural streams, there are costs to wildlife and to people who enjoy and benefit from that wildlife. If you hunt or fish or bird watch or hike, we live in a diminshed landscape.