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Crayfish in Aquatic Crayfish in Ecosystems
Crayfish Habitat Loss
Invasive Crayfish Species
Texas Prairie Crawfish (Procambarus steigmani)
Posted October 16, 2008
There is no way to know for sure how long a prairie crawfish has lived in the area north and northeast of Dallas but it is probable that it has been in residence for an extremely long time. Before the Lone Star, Columbus, and the Kichai, in the same prairie and the same spots as it lives now. A long time. Ancestors to members of the present colonies no doubt saw passing buffalo, lived among the great stands of nine foot grasses, and saw the first cut of the plow.
The Texas prairie crawdad (= crawfish) is an upland creature living in fields rather than ditches, lakes or streams. Home base is a tunnel that extends downward into the earth. There the critter lives with black eyes, waving antennae and bright blue or purple claws protruding from the burrow opening from dusk to dawn. During daytime, it stays safely below, usually at the burrow bottom where the tunnel meets the water table. When disturbed, a prairie crawdad is quicker than most burrowing crawdads in the backward retreat down a burrow hole. Being a deep tunneler, it has a nice weeee drop, to maybe ten feet or more. On wet humid nights, the prairie crawdad emerges to wander a short distance in search of food, a mate or trouble. In times of drought, the Texas prairie crawdad will plug the burrow opening with clay and wait underground for damper times.
Nobody paid much attention to the presence of prairie crawfishes, it seems, until they showed up in snake traps at Parkhill Prairie grassland preserve about 18 years ago. Ken Steigman of the Heard Natural Science Museum and Wildlife Sanctuary, McKinney, took interest in the colorful creatures and had them examined by a crawfish expert at the Smithsonian Institution. The crawfish was determined to be a new species so a description was published and the animal was given the name Procambarus steigmani in honor of the discoverer. Later, reports were made of prairie crawdads from several locations in northeastern Texas.
The presence of prairie crawfishes around the Metroplex represents the lower portion of the range of such crawfishes in North America. Their distribution is within the central prairie, is generally north and west of the Ozark-Ouachita highland from Illinois through Iowa and southward through Missouri, eastern Arkansas, and western Oklahoma across the Red River into northeastern Texas.
The two recognized Texas prairie burrowers are certainly beauties. The females have chocolate brown upper bodies with blue or purple claws. The males have cherry red or reddish brown upper bodies with bright blue claws.
A female of Texas prairie crawfish is the cover girl of a new book on Texas crawdads (See www.texascrawdads.com). This excellent book, Texas Crawdads, serves as a field guide and information source for all of Texas’ 40 crawfish varieties. The authors will have a table at the grand opening of the Audubon Trinity River Nature Center on October 18 and 19. Attendees may review display copies or purchase a book. A set of unique and feisty critters will also be displayed and kids or kids-at-heart will have opportunity to boast about their crawdadding adventures.
Posted August 3, 2008
Some Notes on Texas Crayfish Biodiversity and Conservation
Biodiversity refers to the number of organisms: animals, plants, microbes; all the life that exists within any given geographical area or ecosystem. A diverse ecosystem containing a wide selection of species is more stable than one with fewer species.
Currently there are over 500 described species of crayfish worldwide. More than 350 of those species are found only in North America. The United States is thus the region of greatest crayfish biodiversity for the entire planet. Population status and distribution information for most of North America’s crayfish species has not yet been firmly established. However, some crayfish biologists currently estimate that as many as one half of North American crayfish warrant special concern as regards their conservation status. Four crayfish species are currently listed under the Endangered Species Act.
Crayfish occupy an important position in the food web of aquatic ecosystems. Crayfish consume both animal and plant food. They are predators of benthic organisms and also scavengers of any animal protein that becomes accessible to them. Crayfish also consume living and decaying vegetation, both aquatic plants and terrestrial plant matter that is deposited into the waters crayfish inhabit. Removal of decaying plant materials improves water quality and moves energy up the food chain to larger predators. Crayfish are food for many aquatic and terrestrial animals. Many species of fish, birds, reptiles and amphibians, and mammals all utilize crayfish as a major food source.
Crawfish are ubiquitous aquatic organisms that occupy an important and critical role in healthy stream ecosystems.
Habitat loss is a major threat to Texas crawfish biodiversity. Particularly vulnerable are species occupying a very limited range, or a specialized habitat niche, such as is occupied by the Texas prairie burrower species Procambarus steigmani and Procambarus regalis. Habitat modifications that threaten native crayfish populations include such things as dams which disturb flow regimes and floodplains, urban development and drainage modifications, water pollution, destruction of wetland habitat types, or the lowering of a local water table to below the reach of burrowing species due to groundwater pumping or diversion of natural in-stream flows and recharge. Some species thrive in disturbed habitats. This might be a bad thing if their numbers increase so much that there is a risk of displacing or outcompeting other native species in what local habitat remains undisturbed.
The introduction of invasive species into aquatic ecosystems can result in the decline or disappearance of many native species, crayfish included. Introductions of non-native crayfish can result in the spread of diseases that reduce the population of native crayfish. NEVER release any crayfish into the wild unless you are immediately returning a native crayfish back into the same water body from which it was taken. In addition to the risk of disease, non-native crayfish may also eliminate native species by being more successful breeders or out competing with the native crayfish for the available resources in the habitat or may even prey upon the native crayfish species themselves.
The Rusty Crayfish Orconectes rusticus is native to the Ohio River basin. It is an extremely aggressive crayfish with high fecundity. This crayfish has become a problem invasive species in many places outside of its native range and where introduced is a major threat to native crayfish species; http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=214 O. rusticus introductions have been reported from the Canadian River drainage in New Mexico, it is likely only a matter of time before it is also reported from the Canadian River drainage within Texas.
Historically, responsibility for the introduction of non-native crayfish species has been assigned to fishermen dumping bait crayfish into waters where they do not naturally occur. Most states now have laws prohibiting bait bucket introductions of non-native crayfish, and many states also have laws that regulate crayfish in the aquarium trade. However, a quick search of internet auction sites finds numerous species of native and exotic crayfish advertised for sale and shipment most anywhere. This should create the concern that our native crayfish are increasingly becoming available outside of their native ranges. While this does not guarantee aquarium trade crayfish will become invasive species of concern, it certainly increases the potential for it to occur. A trip to the San Marcos River near my home provides the visual proof of how the aquarium trade has impacted our aquatic ecosystems as regards invasive species introductions.
Another threat to crayfish biodiversity worth mentioning is one we call Crayfish Blindness, a term that can be used to describe a somewhat widespread perception that crayfish are a single specie group of organisms that exist only in the role of fish bait or as the main ingredient of crawfish festival boils.
Regional field guides such as Texas Crawdads encourage people to “see” the various crayfish species that inhabit their regions, to know them as distinct and unique. State or regional crawfish books also educate people to recognize that the crayfish species of places they travel to can be different from those that live in their own region or state.
Once people develop an awareness of the species diversity within a group of organisms and an awareness of their role in the ecosystems they inhabit, people may then become more inclined to have some concern about the possible existence of threats to its survival. Too often conservation efforts are reactive and not proactive, delayed until the effects of biodiversity loss become too obvious to ignore, until the impact of the disappearance of a species begins to be observed in species or habitats that for reasons of aesthetics or economics are considered more important.
Posted June 22, 2008
Texas Parks and Wildlife Rare, Threatened and Endangered Species of Texas: Crayfish
Found here are links to the Texas Parks and Wildlife Department online county data for Rare, Threatened and Endangered Species of Texas. We have included additional comments based on crayfish collections reported in our Texas Crawdads book.
While not included in the TPWD data, two additional Texas crayfish species exist that are each recorded from only a single county. Procambarus brazoriensis, a longpalm crayfish, has only been collected from a few locations in Brazoria County. Procambarus ceruleus, the Navasota Crawfish, has only been collected from locations within Brazos County. While the population status of these two crawfish species is not well understood, they do for now appear to have the two most limited distributions of any of the Texas crayfish species. Certainly both species warrant special concern.
Below are links to TPWD current individual crayfish species data; included below each are new county records not yet reported in TPWD crayfish data.
The range of Cambarellus texanus, a pygmy crayfish, is now known to include Colorado, Ft. Bend, Jackson, Lavaca, Matagorda, and Waller counties. Cambarellus ninae, another Texas endemic, is recorded from only six coastal counties south of the known range of Cambarellus texanus.
Fallicambarus devastator, a fatclaw digger crayfish, is also recorded from Woodland and Pasture habitats in Angelina, Houston, Polk, Trinity, and Tyler counties.
We consider this Texas record for O. maletae to more likely have been Orconectes difficilis.
Procambarus nechesae, one of Texas three endemic slenderclaw crayfish, has also been recorded from Polk County.
We have collected Procambarus nueces, another texas endemic and possibly Texas most rare slenderclaw crayfish, only in Atascosa County. An undescribed species of slenderclaw crayfish is found in five coastal counties south of the Nueces basin.
There are no published records of the crayfish Procambarus steigmani, a prairie burrower, outside of Collin County. Unpublished collection reports and photos of similar crayfish taken in adjacent counties do exist.
Previously reported as occuring in ponds, we have collected Texas third endemic slenderclaw crayfish Procambarus texanus from a stream in Bastrop County. We have collected slenderclaw crayfish from the lower Brazos and Colorado basins whose gonopod structure more closely resemble those of Procambarus texanus than of Procambarus zonangulus.
Posted June 23, 2008
State of Texas - Crayfish Species Checklist
Carnegie Museum of Natural History
Texas Hairclaw Crawfish
Texas Slenderclaw Crawfish
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