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Crayfish Diversity at the ANHC's System of Natural Areas

Arkansas Natural Heritage Commission - Thursday, July 16, 2020
by Dustin Lynch

Gap Creek at Gap Creek Natural AreaOne of my favorite things about my job as the aquatic ecologist for the Arkansas Natural Heritage Commission (ANHC) has undoubtedly been conducting biological inventories of our amazing natural areas. ANHC’s System of Natural Areas, consisting of 75 sites across the state, preserves, maintains and in some cases restores, the best remaining examples of our rarest natural communities and the species that comprise them. Visiting a natural area can offer a glimpse into the past, when our natural landscape was still intact, as well as a moment of respite from the modern world. Almost all these natural areas have at least some sort of aquatic habitat, whether evident or not. From major rivers to headwater streams, from deep caves beneath the earth to ephemeral woodland pools, from murky cypress swamps in the lowlands to crystal-clear, spring-fed creeks in the mountains, our natural areas provide habitat for an astonishing diversity of aquatic species.

One can get a unique appreciation for the role that the system plays in protecting our state’s biodiversity by focusing on the diversity within a single taxonomic group (related group). And what group could be better for this exercise than crayfish? Arkansas has a diverse crayfish fauna (with approximately 60 species occurring here), and I spend much of my time these days studying them at natural areas.

Bubbling Spring at Rock Creek Natural AreaOne of my favorite places to visit in the system is Rock Creek Natural Area (NA) in Sharp County in northeastern Arkansas. Rock Creek is a beautiful tributary of the Spring River, a watershed that is home to many unique species. In addition to Rock Creek itself, this 415-acre natural area is home to the impressive Bubbling Spring and its spring-run tributary to Rock Creek. I have surveyed both the creek and the icy spring run, using a variety of sampling techniques. While seining, kick-seining, or backpack electrofishing are useful methods to document aquatic biodiversity, there is nothing that can quite compare to stream snorkeling, and Rock Creek is one of my favorite places in the state to do it. Actually getting under the water and witnessing the diverse assortment of species that live in an Ozark stream on their own terms can be an unforgettable experience.

Hubbs' CrayfishRock Creek and Bubbling Spring are home to at least four stream-dwelling crayfish species, but perhaps my favorite is Hubbs’ Crayfish (Cambarus hubbsi), a stout and powerfully built species endemic to the Ozark Highlands. This crayfish, which occurs only in permanently flowing, high-gradient streams, is olive-tan in color with a broad, flattened carapace. This species is thought to be somewhat more vulnerable to anthropogenic disturbance (related to human activity) than other crayfish species due to certain life history traits. I have found Hubbs’ Crayfish in Rock Creek itself as well as living in the frigid waters of the spring run close to Bubbling Spring. One thing I always notice right away when I see this species are its exceptionally thick, powerful chelae (pincers). One hazard in my line of work is getting pinched frequently by crayfish. I can say I’ve been pinched by dozens of species at this point, but Hubbs’ Crayfish has the honor of inflicting the most pain!

Hall's CreekAnother interesting site for crayfish in the Ozarks happens to be one of the newest additions to the System, Hall’s Creek Canyon NA in Randolph County. While this natural area is only 33 acres, it protects both fascinating botanical diversity and beautiful, unique geologic features. Hall’s Creek itself, which runs through the steep, bluff-walled canyon, is also part of the Spring River watershed. While the creek is spring-fed, it is also intermittent, meaning portions of it dry up completely in the summer during dry periods, reducing the creek to a series of pools rather than a stream that flows all the way through the canyon.

Mammoth Spring Crayfish at Hall's Creek Canyon NAWhen the ANHC acquired Hall’s Creek Canyon, I was thrilled to conduct the first aquatic surveys of the natural area, suspecting it might be home to a few rare regional endemics. On a survey in the fall of 2019 with Brian Wagner from the Arkansas Game and Fish Commission (AGFC), we discovered that the creek was home to an endemic crayfish with a limited range. The Mammoth Spring Crayfish (Faxonius marchandi) is found only in small streams in the Spring River watershed in two counties in Arkansas and one in Missouri. This unassuming, reddish-brown species with speckled claws can most often be found in gravel or rubble-bottomed riffles (the fast-flowing portions of streams) in clear, unpolluted water, though it may also live in pools (the quieter, deeper portions of the stream), as it does at Hall’s Creek Canyon during summer dry spells.

Williams' Crayfish at DENAIn the far northwestern part of the state, within the Ozark Highlands, at the 3,017-acre Devil’s Eyebrow NA (in Benton and Carroll counties) I made several visits during my first two years working for the ANHC searching for another rare regional endemic crayfish that I suspected I could find there. Williams’ Crayfish (Faxonius williamsi) is notable for a pale vase-shaped marking atop its carapace (which can vary greatly in terms of intensity among individuals). This species prefers small streams, spring-runs, headwaters, and seepages. It is primarily endemic to the upper White River watershed at localities in northern Arkansas and southern Missouri, and it is thought that the creation of impoundments, including Beaver Lake (which lies to the immediate south of Devil’s Eyebrow NA), may have fragmented the species’ range. The karst topography of Devil’s Eyebrow NA includes beautiful clear creeks typified by unique and striking karst features like sinkholes, caves, and bluff shelters. These streams are home to such large concentrations of another Ozark endemic, Meek’s Crayfish (Faxonius meeki), that attempting to find the rarer Williams’ Crayfish there at times felt like looking for a needle in a haystack, but eventually we did document the species there in a small creek near the Missouri state line in November 2018.

Redspotted Stream Crayfish at Gap Creek NAEven the most unassuming of natural areas are home to amazing species. Gap Creek NA, in the Ouachita Mountains (Montgomery County), is only 10 acres, but protects a beautiful upland tributary of the Caddo River that is home to a population of a species found only in Arkansas, the Redspotted Stream Crayfish (Faxonius acares), a species that prefers rapidly flowing water. It is among the most distinctively marked stream-dwelling crayfish in Arkansas, with its pairs of large bright red spots running down its abdominal segments.

Shrimp crayfish at Benson Creek NA

The natural areas in our lowland ecoregions, such as the Mississippi Alluvial Plain (colloquially called “The Delta”) of eastern Arkansas and the West Gulf Coastal Plain in the southern part of the state, are home to some very different species. Benson Creek NA protects 1,459 acres of cypress-tupelo swamp along Bayou DeView in Monroe and Woodruff counties. I’ve found more species of crayfish at this site than any other natural area that I’ve surveyed. In the murky water among the cypress knees of Bayou DeView, I’ve found such diverse and remarkable species as the Painted Devil Crayfish (Lacunicambarus ludovicianus), the Red Swamp Crawfish (Procambarus clarkii), and the bizarre-looking Shrimp Crayfish (Faxonius lancifer), a species thickly dusted in black speckles and mottling with an unusually long rostrum (“nose”) and miniscule, weak pincers, which causes it to resemble some strange combination of a shrimp and a crayfish.

Devil Crayfish at Lorance Creek NAWhile we often tend to think of the most important areas of biodiversity as being in remote places in the wilder corners of the state, this is by no means always the case. In central Arkansas, not far south of Little Rock, Lorance Creek NA (389 acres, in Pulaski and Saline counties) is home to several interesting crayfish species that inhabit the shallow, groundwater-fed swamp along both sides of the creek. The swampy habitat is home to hazards such as cypress knees and several feet of soft mud on the creek bottom that make it a real challenge to survey using seines, dip-nets, or even backpack electrofishing. A much more effective method of sampling at Lorance Creek is setting minnow traps overnight. The moment you haul a trap up out of the swamp the next morning can be magical, as you anticipate what sort of aquatic species you might find. In my traps at Lorance Creek, I’ve gotten such species as the strikingly patterned Ouachita River Crayfish (Procambarus ouachitae) and the stout, powerful Devil Crayfish (Lacunicambarus diogenes).

Palmetto Flats Natural AreaIn far southwestern Arkansas, in the West Gulf Coastal Plain ecoregion, Palmetto Flats NA (Little River County) protects 1,848 acres of alluvial terrace forest, including wet flatwoods, seeps, sloughs, and marshes. Alongside the cottonmouths, bullfrogs, and alligators that call the swamps in this corner of the state home, one can find a rather a rather unassuming, diminutive regional endemic known only from the Red River basin in southwest Arkansas and adjacent portions of Oklahoma and Texas. The globally rare Blair’s Fencing Crayfish (Faxonella blairi) grows no more than a couple inches in length. Fencing crayfish (Genus Faxonella) are so named for the shape of their gonopods (the male sexual organs), which are long, slender, and are carried with the tips crossed over one another like a pair of fencing swords. These tiny crayfish can be found in the sloughs, flooded ditches, and wet flatwoods of the natural area. This species is considered a secondary burrower, one that constructs burrows of some complexity down to the water table, but often near surface waters. Secondary burrowers may shift between living underground and at the surface depending on seasonal cycles of drying.

Blair's Fencing Crayfish at Palmetto Flats NAMy surveys of natural areas have taken me to every corner of the state, from mountainsides to swamps, from huge rivers to modest ephemeral creeks, and at most of them I’ve found at least one species of crayfish living there, whether in a stream, a swamp, or a burrow beneath the ground. At first glance, crayfish may appear to be a somewhat homogeneous group, but they are incredibly diverse. An appreciation for that diversity mirrors appreciation for the natural landscape of our beautiful state.



Photos (top to bottom):

Gap Creek at Gap Creek Natural Area (NA), habitat for Redspotted Stream Crayfish (Faxonius acares). Photo by Dustin Lynch.

Bubbling Spring at Rock Creek NA, a spring-run tributary to Rock Creek. Rock Creek NA provides habitat for the Hubbs' Crayfish (Cambarus hubbsi). Photo by Dustin Lynch.

Hubbs' Crayfish (Cambarus hubbsi) at Rock Creek NA. Photo by Dustin Lynch.

Hall's Creek at Hall's Creek Canyon NA, habitat for the Mammoth Spring Crayfish (Faxonius marchandi). Photo by Dustin Lynch.

Mammoth Spring Crayfish (Faxonius marchandi) at Hall's Creek Canyon NA. The Mammoth Springs Crayfish is an endemic crayfish and found only in the Spring River watershed in two counties in Arkansas and one in Missouri. Photo by Dustin Lynch.

Williams' Crayfish (Faxonius williamsi), a rare endemic crayfish, at Devil's Eyebrow NA. Photo by Dustin Lynch.

Redspotted Stream Crayfish (Faxonius acares) at Gap Creek NA. Photo by Dustin Lynch.

Shrimp Crayfish (Faxonius lancifer) at Benson Creek NA. Photo by Dustin Lynch.

Devil Crayfish (Lacunicambarus diogenes) at Lorance Creek NA. Photo by Dustin Lynch.

Wet flatwoods at Palmetto Flats NA, habitat for the rare Blair's Fencing Crayfish (Faxonella blairi). Photo by Dustin Lynch.

Blair's Fencing Crayfish (Faxonella blairi) at Palmetto Flats NA. Photo by Dustin Lynch.



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