iiinova — where your digital self keeps evolving

Eric R. Larson @ericrlarson.bsky.social · 04/09/2026

I spent my first thirty years across Wyoming (1982-1992), Texas (1992-2000), Idaho (2000-2005), Arkansas (2005-2007), and Washington State (2007-2011), and I'm always impressed these things triangulate that background reasonably well. But crayfish/crawfish/crawdad is a trap for me.

Dialect map with warm colors (match) to the western US grading to coldest or mismatched colors in the southeast and especially northeast

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Eric R. Larson @ericrlarson.bsky.social · 04/09/2026

With colleagues across museums in the US and Canada, we recently asked: what is North America's largest crayfish species? Which led to a more interesting follow-up question: why do the contenders all cluster at a similar upper size limit? New in Ecology at: doi.org/10.1002/ecy....

Dorsal view of a crayfish in a glass jar centered on its carapace. It is not a contender for largest in North America.

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Eric R. Larson @ericrlarson.bsky.social · 21/08/2026

And I guess as a bonus: in the past 10-15 years, we've seen rusty crayfish populations crash in some of their invaded lakes. We'd like to know why. One possibility is a parasite called porcelain disease (studied by my colleagues like Lindsey Reisinger), that appears as milky tissue under the tail.

A ventral view of a crayfish with milky or opaque muscle tissue under its tail or abdomen

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Eric R. Larson @ericrlarson.bsky.social · 21/08/2026

A half century of invasive crayfish monitoring in northern Wisconsin continued this week with Cornell's recently retired David Lodge and first year University of Illinois PhD student Kaylin Wallen

Two researchers sit in the bow of a john boat with a bucket full of crayfish and a lake in the background under overcast skies

Roughly two dozen rusty crayfish in a shallow white bucket

A flowage between two lakes in northern Wisconsin with bright green vegetation on both shores under a sunny sky with scattered clouds

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Eric R. Larson @ericrlarson.bsky.social · 26/07/2026

Another summer looking for the rare, native Pilose Crayfish (Pacifastacus gambelii) throughout the Bear River watershed of Wyoming, Idaho, and Utah

A researcher kicks through substrate while another researcher stands downstream holding a seine in a shallow, wadeable creek

A mottled red crayfish seen in the bottom of a white five gallon bucket

Upstream view of a small cascade in a creek with an arid mountain in the background under overcast skies

Two researchers measuring the width of a rocky stream with scattered cottonwoods on the floodplain in the middle distance

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Eric R. Larson @ericrlarson.bsky.social · 19/05/2026

Always nice when the Society for Freshwater Science meeting is directly on a river #2026SFS

Wide, blue river passes under a tall concrete arch bridge

Clock tower over a placid, impounded river pool beneath a blue and pink dusk sky

Waterfall with a small rainbow in its mist looking across to a tall, concrete arch bridge on the opposing bank

Cobble seen on a riverbed through a still pool with a square clock tower on the opposite bank

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Eric R. Larson @ericrlarson.bsky.social · 19/05/2026

Was fantastic to celebrate David Lodge's career and outsized impact in invasive species research and policy at #2026SFS this week, and catch up with so many friends and colleagues working on these important topics

Roughly a dozen conference attendence standing on a stage before a project screen, from left to right: Matt Barnes (Texas Tech), Lindsey Reisinger (University of Florida), Eric Larson (University of Illinois), John Drake (University of Georgia), Bill Perry (University of Minnesota Duluth), David Lodge (Cornell), Romi Burks (Southwestern University), Kristy Deiner (Simplex DNA), Kara Andres (Illinois State University), Jon Bossenbroek (University of Toledo), Reuben Keller (Loyola University Chicago), Andy Mahon (Central Michigan University), and Chris Jerde (University of California Santa Barbara)

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Eric R. Larson @ericrlarson.bsky.social · 10/04/2026

Because of the Robert Plant circulating this week: spanakopedia.ordoliberal.com/subtitle/979...

Brock Sampson to H.E.L.P.eR: "Yes, and hobbits, too."

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Eric R. Larson @ericrlarson.bsky.social · 27/03/2026

Multi-metric indices are used to measure biological integrity in response to the US Clean Water Act. But can environmental DNA (eDNA) metabarcoding plug into these existing tools? Our attempt for streams and rivers of Alabama now open access at the journal Environmental DNA: doi.org/10.1002/edn3...

A four panel (2 x 2) image of streams in northern Alabama with bedrock banks and forested riparian zones

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Eric R. Larson @ericrlarson.bsky.social · 12/02/2026

Sort of? But it was always a series of streaks: Idaho won 12 straight into the 90s, and then Boise State dominated (12 straight) after both moved up to D-1A. But the overall series stands at 22-17-1. I think the streakiness contributes to the nastiness - Vandals expected to win but the world change.

Idaho versus Boise State football series results from Wikipedia at https://en.wikipedia.org/wiki/Boise_State%E2%80%93Idaho_football_rivalry

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Eric R. Larson @ericrlarson.bsky.social · 14/01/2026

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

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.

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Eric R. Larson @ericrlarson.bsky.social · 12/01/2026

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.

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.

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Eric R. Larson @ericrlarson.bsky.social · 12/01/2026

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....

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.

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Eric R. Larson @ericrlarson.bsky.social · 21/12/2025

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.

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.

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Eric R. Larson @ericrlarson.bsky.social · 06/12/2025

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.

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.

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Eric R. Larson @ericrlarson.bsky.social · 04/12/2025

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.

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.

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Eric R. Larson @ericrlarson.bsky.social · 03/12/2025

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.

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.

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Eric R. Larson @ericrlarson.bsky.social · 03/12/2025

Riparian buffers help more than just streams and rivers in agricultural landscapes. Lab Masters student Olivia Reves used environmental DNA (eDNA) to quantify the benefit of riparian buffers to terrestrial wildlife in downstate Illinois; open access at doi.org/10.1111/1365...

A figure showing a stream without a forested riparian buffer in the top panel and a stream with a forested riparian buffer in the bottom panel. A cartoon water bottle with a DNA symbol in each water bottle directs to adjacent insets with silouttes of representative wildlife at each stream, with the forested stream having more species and including amphibians, reptiles, bats, and flying squirrels.

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Eric R. Larson @ericrlarson.bsky.social · 10/11/2025

New invasion note from southern Idaho, where we've rediscovered the non-native red swamp crayfish after a half century without detection (doi.org/10.3391/bir....). Intensive burrowing by red swamp crayfish could be a risk to canals and other irrigation infrastructure.

An irrigation ditch centered in the image that has dried to a single, isolated pool in the foreground. There are grassy banks on either side of the ditch, with two men standing on the right bank in an orange sweatshirt and blue shirt.

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Eric R. Larson @ericrlarson.bsky.social · 24/09/2025

New faculty position in the University of Illinois Department of Natural Resources and Environmental Sciences for an assistant or associate professor of agroecology: illinois.csod.com/ux/ats/caree.... Position closes October 31st. Happy to answer questions about the dept / university / town.

A prairie with a wetland in the middle distance and a tree line on the horizon under low, scattered clouds

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Eric R. Larson @ericrlarson.bsky.social · 06/09/2025

Completed my annual trip to northern Wisconsin, continuing population monitoring of invasive rusty crayfish (Faxonius rusticus) that extends back to the 1970s. Populations remain down, at only ~25% of past peak abundances, with surprising catches of large native snails in our traps.

A slightly out of focus rusty crayfish (Faxonius rusticus) held between a thumb and forefinger with the calm surface of a lake in the background

Two boats docked in the foreground of a large lake with a yellow floating platform in the middle distance and a forested shoreline ~2 miles back on the horizon

Sunset on a large, calm lake as a band of orange below emerging stars

A square white bucket with ~16-20 rusty crayfish (Faxonius rusticus) waiting to be counted and measured

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Eric R. Larson @ericrlarson.bsky.social · 20/08/2025

This pool was packed with non-native virile crayfish; we recovered >120 in only four traps. It will likely dry out by the end of summer, but virile crayfish have dispersed through this intermittent reach. We found them abundant in the permanent stream higher up the watershed (photos 2 & 3).

An olive brown crayfish held between a thumb and finger with a drying stream pool out of focus in the background.

A small but rocky stream below a blue sky, flowing through sagebrush steppe.

A view from a bridge crossing down into a stream bed of cobble and fine sediments, where one crayfish is visible crawling on a rock.

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Eric R. Larson @ericrlarson.bsky.social · 19/08/2025

So ... any crayfish in this small and declining habitat?

A drying stream pool above a culvert, with a researcher collecting crayfish traps. Five gallon buckets, crayfish traps, and a clipboard are visible on the stream bank.

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Eric R. Larson @ericrlarson.bsky.social · 19/08/2025

Our search for invasive crayfish barriers includes more than just dams or irrigation diversions. Because the virile crayfish is intolerant of stream drying (doi.org/10.1086/725318), intermittent reaches could present barriers to upstream spread to permanent streams in the mountains.

An isolated stream pool above a culvert (not visible, where the photographer is standing) with a dry bed upstream. The pool is turbid and surrounded by dry steppe, with mountains visible in the distance under a mostly sunny sky.

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Eric R. Larson @ericrlarson.bsky.social · 08/08/2025

Here an abundance of crayfish claws and carapaces have been cleaned out of center pivot irrigation filters that had clogged. In our study region, many farmers and ranchers identify this as a problem, but I don't think anyone has quantified these type of impacts of invasive crayfish to agriculture.

A pile of debris on grass that features many obvious crayfish claws and carapaces, cleared from a filter on center pivot irrigation that had clogged

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Eric R. Larson @ericrlarson.bsky.social · 08/08/2025

The non-native virile crayfish (Faxonius virilis) in particular has boomed in regions of the western US without any native crayfishes like the Colorado River (nas.er.usgs.gov/queries/Fact...). Given its abundance in irrigated lands, I wonder if we're missing damages and costs as an ag pest?

A map from the United States Geological Survey's nonindigenous aquatic species database showing the native range of the virile crayfish (Faxonius virilis) as light brown and non-native watersheds as a dark red. The species has a broad native range spanning the Great Plains, upper Mississippi River, and Great Lakes basin, but now occurs as a non-native species west of the continental divide and in Atlantic-draining watersheds of Appalachia. It's probably the most widespread non-native crayfish in North America, but is minimally studied relative to invasive crayfishes with more global distributions like the red swamp crayfish (Procambarus clarkii).

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Eric R. Larson @ericrlarson.bsky.social · 08/08/2025

I routinely get calls from water management districts in southern Idaho concerned about damage to canals from burrowing by this same non-native crayfish. In estimates of economic costs of invasive crayfish (doi.org/10.1016/j.sc...), I think we're missing effects on agriculture in the western US.

An irrigation diversion with sloughing banks that, on closer inspection, were full of crayfish burrows. Mountains and patchy clouds are visible in the background behind dense grass.

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Eric R. Larson @ericrlarson.bsky.social · 07/08/2025

This was another barrier where non-native crayfish passage was obvious before we started sampling. Here a small gate in one of the water control structures was clogged with carcasses from the upstream pool. I think this barrier is open to flow at times of the year when crayfish are moving around.

A cat door-sized panel in a water control structure or dam that is partially open but clogged with debris, letting out a small flow of water.

A close-up of a small panel or gate in a water control structure that is clogged with both aquatic plant debris and noticeable crayfish carcasses, including visible walking legs and abdomens

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Eric R. Larson @ericrlarson.bsky.social · 06/08/2025

This irrigation diversion looked promising as an invasive crayfish barrier. The diversion gates didn't appear to be climbable. Water is diverted into a buried pipe with screens to prevent fish entrainment. Concrete retaining walls extend into the riparian zone. Can crayfish get over or around this?

An irrigation diversion in an arid landscape backing up water behind it, with a shallow, rocky stream below. The diversion consists of a series of concrete retaining walls and metal water controls that can be raised or lowered.

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Eric R. Larson @ericrlarson.bsky.social · 01/08/2025

A relief to add a new pilose crayfish site this week. This native species disappeared from the mainstem, low elevation Bear River in Wyoming between 1987 & 2007, replaced by the non-native virile crayfish (peerj.com/articles/5668/). Remnant populations are confined to higher elevation tributaries.

A pilose crayfish (Pacifastacus gambelii) held close to the camera with a five gallon bucket and clipboard out of focus in the background on a grassy river bank. The pilose crayfish is mottled olive brown and yellow, with distinctive strips of hair on the lateral, dorsal surface of its visible claw.

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Eric R. Larson @ericrlarson.bsky.social · 31/07/2025

Freshwater invaders pose unique challenges to species distribution (or ecological niche) models used in risk analysis. New in Freshwater Science (doi.org/10.1086/737200), I identify strategies to improve predictions of suitable habitat for emerging, data-poor freshwater invaders using these tools.

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Eric R. Larson @ericrlarson.bsky.social · 31/07/2025

One challenge in our work is that although considerable effort has been directed at fish passage and barriers in the study watershed, crayfish and fish differ in what barriers they can and can't pass (e.g., doi.org/10.1016/j.bi...).

Water plunging over a small concrete wall into a downstream, rocky river shot at a low angle to the stream, with a riparian forest of willows and aspen in background below a partly cloudy sky.

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Eric R. Larson @ericrlarson.bsky.social · 31/07/2025

It didn't take much investigation here to conclude this wasn't a barrier to crayfish. We start from a variety of databases in our study watershed (e.g., doi.org/10.1002/rra....) to identify prospective barriers, but need to get in the stream to check out the structure and look for crayfish above it.

A researcher in chest waders holding a measuring tape and clipboard standing in a shallow, rocky river downstream of a concrete water control structure that is at grade with both the upstream and downstream bed of the river. The water control structure might be slippery or hard to walk across for a crayfish, but current velocity was too low to exceed the swimming ability of crayfish.

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Eric R. Larson @ericrlarson.bsky.social · 30/07/2025

Here's another potential invasive crayfish barrier: a concrete structure extending across a river channel associated with a municipal water supply diversion. Can crayfish get over/around this, or not?

A view across a river channel centered on a small concrete dam or water control structure, which extends into the riparian zone and has a noticeable drop or plunge at its downstream end. The river is shallower and rocky below the dam and deeper above.

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Eric R. Larson @ericrlarson.bsky.social · 29/07/2025

More hints that one of our study sites is a good place to catch crayfish

A latrine pile of crayfish fragments with a low gradient river in the background

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Eric R. Larson @ericrlarson.bsky.social · 29/07/2025

There's excellent barrier work in Europe, and in the US emphasis on protecting ESA-listed Shasta Crayfish from invaders (doi.org/10.1093/jcbi...). We're working from existing literature and reports to assess barriers by flow velocity, vertical drop, and risk of climbing or overland passage.

A two panel figure cropped from a scientific journal article, where the left panel (C) shows a crayfish barrier extending across a spring system as a stainless steel wall; you can't tell from this image that the barrier is submersed but using the high rate of water flow from right to left to exclude crayfish from swimming over the barrier. The right panel (D) shows a more vertical drop barrier where stainless steel walls adjoin a high-velocity spillway with about a half foot drop downstream. This would likely be fish passable (can jump from the downstream plunge pool) but not crayfish passable.

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Eric R. Larson @ericrlarson.bsky.social · 24/07/2025

Here's another potential invasive crayfish barrier: a road crossing above a concrete slab with a drop to a downstream pool. In this case we couldn't assess if the barrier was passable because we found no crayfish up or downstream of the road, likely because the stream is intermittent.

Road crossing a stream above a concrete slab with a 2-3 foot drop above a downstream pool. The stream is not flowing and clumps of algae are visible in the standing water. A crayfish trap is visible in the bottom left corner.

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Eric R. Larson @ericrlarson.bsky.social · 23/07/2025

For sick or dead crayfish, we're especially looking for porcelain disease, which causes milky or opaque muscle tissue under the abdomen, or the crayfish plague, which might look like lesions or melanized spots on the exoskeleton

A relatively fresh (non-stinky) crayfish mortality in-hand with a rocky lake beach in the background

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Eric R. Larson @ericrlarson.bsky.social · 23/07/2025

Yeah, crayfish store calcium in stomach stones or gastroliths to help remineralize their exoskeleton after a molt. The stomach stones look like little white pills or pebbles and are durable enough to be routinely found on the shores of rivers and lakes.

A crayfish gastrolith or stomach stone, as a small white circle of mineral, held in a human hand above a stream in the background

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Eric R. Larson @ericrlarson.bsky.social · 23/07/2025

We found many crayfish remains on the shore at this site, where I think they were driven to an exposed point by the prevailing wind. Disease transmission is a big risk from invasive to native crayfish, so we're always looking for evidence of disease or mass mortality events.

A row of seven large crayfish claws and one carapace with both claws against a rocky shoreline. The claws all share the diagnostic hairy patches of the pilose crayfish (Pacifastacus gambelii).

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Eric R. Larson @ericrlarson.bsky.social · 23/07/2025

You can definitely find crayfish remains associated with predators. Here we have some crayfish fragments, including gastroliths or stomach stones, outside a den in a river bank. But at high density populations there are tons of molts, and those claws or other exoskeleton pieces can wash up on shore

Fragments of crayfish, including a partial carapace, claws tips, and small, white stomach stones or gadtroliths, on a background of green algae on a river bank. This was directly in front of a deep den or burrow of a mammal predator into the bank (outside of the image).

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Eric R. Larson @ericrlarson.bsky.social · 23/07/2025

Sometimes we know a crayfish is at a site before we even begin sampling. In this case, the hairy claws of the pilose crayfish had washed up on the shore of a reservoir from molts or mortalities.

A crayfish claw with hairy patches on the left and right dorsal surface, with an out of focus lake in the background

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Eric R. Larson @ericrlarson.bsky.social · 23/07/2025

This wasn't a big surprise - the irrigation diversion has a fish passage channel where the shallow, stepped dam boards are a fish ladder (out of view around the bend in this photo). Maybe we'll find a more robust invasive crayfish barrier farther upstream?

Irrigation diversion with spillway, two culverts, and a rocky fish passage channel in the distance with dry mountains in the far background. It's warm and windy. We're acclimating from a heavier atmosphere in Illinois. We'll survive.

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Eric R. Larson @ericrlarson.bsky.social · 23/07/2025

This was the first potential barrier we checked this summer, and we immediately found a virile crayfish showing us some technique for climbing over the dam boards. Definitely not a barrier - virile crayfish abundant upstream of the diversion

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Eric R. Larson @ericrlarson.bsky.social · 22/07/2025

This summer, my lab is working to determine whether we can protect the rare, native pilose crayfish in Wyoming from the widely invasive virile crayfish. For example, do irrigation diversions work as barriers excluding virile from pilose habitat? So: what do we think of this prospective barrier?

The pilose crayfish (Pacifastacus gambelli), a mottled crayfish with patches of dense hairs on the dorsal surface of its claws. It's native to the upper Snake River and Bonneville Basin watersheds of Idaho, Nevada, Utah, and Wyoming, awfully hard to find, and largely replaced from its historic occurrences by the non-native virile crayfish.

The virile crayfish (Faxonius virilis), the most routine looking crawdad you've ever seen, held between a thumb and forefinger with a shallow stream in the background.

Half of an irrigation diversion showing water spilling through dam boards above a concrete spillway before a short drop to the downstream pool

The other half of an irrigation diversion showing a high rate of water flow through a culvert

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Eric R. Larson @ericrlarson.bsky.social · 08/07/2025

New from my colleagues at the University of Illinois: a dataset of vascular plant species presence for 353 prairie remnants across the Midwestern United States (doi.org/10.3375/2162...)

A map of the historical extent of the tallgrass prairie (gray) and 319 sampled remnants (black circles) in RELIX across the Midwestern United States. 34 remnants are not shown on the map since they did not have precise location information.

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Eric R. Larson @ericrlarson.bsky.social · 03/07/2025

Another example of the power of environmental DNA (eDNA): a positive eDNA detection led to the rediscovery of a freshwater mussel not found live in Illinois for over a century. New student-led, open access paper in Ecology with @markdavis79.bsky.social at doi.org/10.1002/ecy....

A four panel figure showing (a) a biologist wading in a turbid river with a water sample, (b) a real-time or quantitative PCR amplification plot with a positive environmental DNA detection, (c) a biologist searching concrete riprap on a river bank, and (d) two freshwater mussels that have been marked for future monitoring and recapture.

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