Ouachita Crayfish

Crayfishes are an important part of aquatic habitats as they are often the largest and most common invertebrates in streams and lakes. Crayfishes serve as an important food source for many game and nongame fishes such as smallmouth bass, and wildlife such as otters, minks, weasels, and raccoons. They facilitate important ecological processes, sustain recreational and commercial bait fisheries, and serve as profitable and popular food resources (Taylor et al., 1996).

Unfortunately, little has been done in regard to the scientific study of crayfishes in Arkansas and Oklahoma in general and in the Ouachita Mountains physiographic region in particular. Although often encountered by professional biologists, fishermen, and naturalists alike, the main deterrent to a critical understanding and appreciation of crayfishes by the nonspecialist lies in the certain difficulty in identifying them to species. Except for Williams' (1954) monograph on crayfishes of the Interior Highlands, biologists and resource managers have little valid information in one source as to which crayfish species occur within their particular areas. There is other technical literature on individual crayfish species; however, it is scattered through a plethora of scientific journals and books.

The present study of the crayfishes of the Ouachita National Forest (ONF) in Arkansas and Oklahoma was initiated in an effort to elucidate the crayfish fauna of this geographic area (Map 1). Such a study has great utility to professional resource managers responsible for the wildlife component of the Ouachita National Forest ecosystem.

The purposes of this study were primarily four-fold: (1) to determine the species of crayfishes inhabiting the ONF in Arkansas and Oklahoma; (2) to assess the abundance and distributional limits of the crayfish species within the ONF; (3) to gather life history information seasonally on the various species of crayfishes within the Forest; and (4) to assess the current status of each of the crayfish species based upon distributional and abundance data assembled from this study.

MATERIALS AND METHODS

Field work for the Arkansas part of this project was conducted from April, 1996 through October, 1997. A few Arkansas ONF collections were added from the spring of 2000. A total of 256 collections of crayfishes was made which resulted in 2,337 individuals collected in an effort to document the crayfish fauna of the Arkansas portion of the Ouachita National Forest (Table 1, Map 2).

Field work in Oklahoma began in September, 1998, and continued through July, 2000. A total of 204 collections of crayfishes resulting in 1,192 individuals was made in the ONF areas in Oklahoma (Table 2, Map 3).

Many of the specimens were released unharmed following careful identification while voucher series were made of others. Collecting localities visited during the three-year study are shown in Maps 4 and 5. Collecting was concentrated in the ONF streams and rivers and additionally in wet seepage areas specifically for burrowing crayfish species. Much of the field work occurred during the fall, spring and summer to utilize optimal field conditions.

A variety of collecting methods was used in the documentation of the ONF crayfish fauna including the use of common sense minnow seines, one-man seines, electroshocking equipment, aquatic dip nets, baited and unbaited crayfish traps, and by physically digging the burrowing specimens from their burrows.

Selected specimens were kept alive in a cooler and transferred to Southern Arkansas University in Magnolia, AR, where photographs were made of the best specimens. Representative specimens from each collecting site were preserved in 60% isopropyl alcohol for later study. Preserved specimens were deposited in the Southern Arkansas University Invertebrate Collection and the Smithsonian Institution Crayfish Collection after careful study of individual variation among species.

In addition to collections made during this survey, museum specimens housed at the Smithsonian Institution, Washington, D.C., and Southern Arkansas University were studied to document the identifications and distributions of the crayfish species. All previous literature dealing with Arkansas and Oklahoma crayfish species was reviewed and distributional information was utilized when deemed accurate.

HISTORICAL REVIEW BY STATE

Review of Arkansas Portion

The first recorded mention of a crayfish from the state of Arkansas was Hagen (1870). Few additional references can be found to Arkansas crayfishes until the late 1940s and 1950s. Of special importance to students of crayfishes of the Ouachita Mountains of Arkansas is Williams (1954). Although outdated now, it remains the foundation from which to start any serious investigation of area crayfishes. Reimer (1963) completed a master's thesis on the crayfishes of Arkansas and included records for the Ouachitas.

Bouchard and Robison (1980) presented an inventory of the species of crayfishes living in Arkansas and provided data on general habitats of crayfishes in all physiographic regions of the state. Hobbs and Robison (1988) described two new species of Procambarus from Arkansas and provided a key to all of the species of the burrowing subgenus Girardiella. In addition, distributional information was updated on all species of the subgenus. Hobbs and Robison (1989) investigated the Arkansas species of the burrowing crayfish genus Fallicambarus and described two new species from the state.

Review of Oklahoma Portion

The first survey of Oklahoma crayfishes was by Creaser and Ortenburger (1933) who reported 10 species as occurring in Oklahoma, one of which was considered by Reimer (1969) to be erroneous. Thirty years later, Reimer (1969) reported 19 species and subspecies of crayfishes inhabiting Oklahoma. More recently, Taylor et al., (1996) refined the Oklahoma crayfish species list to 23 species occurring within the state including four species of Cambarus, one species each of the genera Fallicambarus and Faxonella, eleven species of Orconectes, and six species of Procambarus. Hobbs H. Hobbs, III provided the most recent addition to the Oklahoma state crayfish fauna in 1993 when a cave species, Cambarus subterraneus, was officially described (Hobbs, 1993).

DESCRIPTION OF THE AREA

The Ouachita National Forest (Map 1) is the oldest and largest National Forest in the South, comprising 1,775,507 acres in Arkansas and Oklahoma (Mr. Richard Standage, pers. comm.). Of this total, 1,424,439 acres of the ONF occur in Arkansas and 351,068 acres of the ONF occur in Oklahoma. In Arkansas the ONF is situated primarily in the Ouachita Mountains physiographic region and contained within portions of Montgomery, Polk, Garland, Logan, Perry, Scott, and Yell counties. In Oklahoma, the ONF is situated primarily in the southwestern Ouachita Mountains in LeFlore and McCurtain counties; however, a disjunct section of the ONF, the Tiak District, occurs in southern McCurtain County, Oklahoma.

The entire ONF is dissected by three large river drainages: the Arkansas River drainage to the north and west and the Red River (Kiamichi and Little River systems) and Ouachita River drainage in the southern portion. River systems of the Arkansas River drainage within the ONF include the Poteau River, Petit Jean River, and Fourche la Fave River. The Red River drainage includes the Kiamichi River system and the Little River system which is represented by the Mountain Fork River, Cossatot River, western Saline River, Glover River, and Little River while the Ouachita River drainage is represented by the mainstem Ouachita River, Caddo River, Little Missouri River, eastern Saline River (with its three forks), and a multitude of smaller tributaries.

GENERAL ASPECTS OF CRAYFISHES

General Considerations

Crayfishes are a most important and integral component of aquatic ecosystems found throughout Arkansas and Oklahoma. In many streams, sport fishes such as sunfishes and basses (Family Centrarchidae) may consume up to two-thirds of the annual production of crayfishes (Taylor et al., 1996). Crayfishes contribute to the maintenance of food webs by processing vegetation and leaf litter (Huryn and Wallace, 1987; Griffth et al., 1994), which increases the availability of nutrients and organic matter to other aquatic and terrestrial organisms.

Crayfishes are members of the most numerous of all animal groups, the arthropods or joint-legged animals. They are classified as crustaceans because of their possession of two pair of antennae and the fact that they breathe by gills. Crayfishes are protected by a heavily armoured exoskeleton and have five pairs of walking legs, the first of which functions as enlarged pincers called chelipeds (Figure 1).

Approximately 450 species of crayfishes occur worldwide and about 338 are found in the United States and Canada (Pflieger, 1996; Taylor et al., 1996). Arkansas has 53 crayfish species (Bouchard and Robison, 1980; Taylor et al., 1996; H. W. Robison, personal data) belonging to one family, Cambaridae, and classified into seven genera. The genus Procambarus slightly dominates the crayfish fauna of Arkansas with 18 species, while the genus Orconectes is represented by 16 species, Fallicambarus with eight species, Cambarus with six species, Cambarellus and Faxonella with two species each, and Bouchardina with a single species. Several additional undescribed species of crayfishes are known from Arkansas, but formal scientific descriptions of them are not yet completed.

Oklahoma has 23 crayfish species recorded from within its state boundaries (Reimer, 1969; Taylor et al., 1996) contained within the family Cambaridae and classified into five genera. The genus Procambarus is represented in Oklahoma by six species, while Orconectes is the dominant genus with 11 species, and the genus Cambarus contains four species, with both Faxonella and Fallicambarus having a single species within the state.

Prior to discussion of the various crayfishes documented from the ONF, a brief overview of several basic life history aspects involving crayfishes, general taxonomic points, and ecological considerations are presented.

Basic Life History Cycle

Although highly variable, most crayfishes in Arkansas and Oklahoma mate between September and March. Form I males (breeding males) seek out receptive females and mating is accomplished. Sperm are carried by the female until oviposition (egg laying) which may be in March, April and May, although some species begin as early as December or January (Page, 1985). Following oviposition, the eggs are attached to the underside of her abdomen and females are said to be ovigerous or "in berry." Females carry the eggs for 2-20 weeks depending on the water temperature (Page, 1985). After hatching, young move quickly through a series of molts until sexual maturity is reached by late summer or early fall.

Little is known about the specifics of the life cycles of the particular species which inhabit the Ouachita National Forest. Hopefully, future research on the crayfishes of the ONF will remedy this current lack of knowledge.

Taxonomic Considerations

The taxonomy of North American crayfishes is based upon numerous morphological characteristics (See Hobbs, 1972a) The secondary sexual characters are actually the most important for identification purposes, such as the annulus ventralis, copulatory hooks, bosses on the coxae of some periopods (walking legs), and first pleopods (Bouchard and Robison, 1980). The morphology of the male's first pleopods is the single most important character in identifying most species and practically all of the genera of North American crayfishes, including the crayfishes of the ONF.

In crayfishes of the family Cambaridae, adult males exhibit two morphological forms during the year, molting into these conditions with only the first form (form I) males capable of breeding. The second form, or form II male is sexually nonfunctional (Bouchard and Robison, 1980). The first pleopod (or gonopod) of the form I male has delicate, finely sculptured elements, at least one of which consists of amber, corneous material. The first pleopod of the form I male is easily distinguished from the form II gonopod which has elements usually reduced in length and/or more inflated and without a corneous deposit (See Hobbs, 1972a). Also reduced in size are the remaining secondary sexual characters such as the chelae.

It is therefore many times imperative to the person wishing to identify the species in question to have a first form male to make positive identifications. Juveniles and female specimens are always more difficult to identify to species level.

Ecological Categories

The crayfishes of both Arkansas and Oklahoma can be grouped into three broad, overlapping, ecological categories (Reimer, 1969; Bouchard and Robison, 1980). There are those species that inhabit the diverse surface water habitats (epigeaners), those species that utilize underground solution channels in limestone regions (cavernicoles), and those species that burrow into the subsurface water table (burrowers). Because these categories are not rigid, there is some overlap among groups.

Hobbs (1942) recognized three categories of burrowers and this classification has been found useful to crayfish workers, i.e. primary burrowers, secondary burrowers, and tertiary burrowers. Hobbs (1981) characterized primary burrowers as crayfishes that spend almost their entire lives below the surface of the ground, only occasionally leaving their lairs on brief forays on land, presumedly searching for food, and at times, a mate. Seldom are the burrows in connection with bodies of open water. Primary burrowers inhabit burrows where for most of the year the water table does not drop more than a meter or so beneath the surface. Typically these areas may be easily recognized by the presence of hydrophilic sedges. Many times these areas occur near the roadbed. Secondary burrowers generally occupy burrows but may wander into the open water during rainy periods. Tertiary burrowers burrow only in periods of drought or occasionally during the breeding season. The rest of the year they inhabit streams or other permanent or semi-permanent bodies of water.

CRAYFISHES OF THE OUACHITA NATIONAL FOREST

ONF: Arkansas and Oklahoma

A total of 18 species of crayfishes classified in four genera (Fallicambarus, Faxonella, Orconectes, and Procambarus) was documented from the entire Ouachita National Forest in Arkansas and Oklahoma during the four-year study (Table 3). Of this total (18), 14 crayfish species were documented from the Arkansas portion of the ONF while eight species were documented from the Oklahoma portion of the ONF. Only four species occurred in both state portions of the ONF. Those four crayfishes which occurred in both state portions of the ONF were Orconectes palmeri, Orconectes leptogonopodus, Procambarus acutus, and Procambarus tenuis.

Approximately 4,529 individual crayfish were collected in 460 separate collections from the ONF during the four-year study in an effort to document the crayfish fauna of the ONF in Arkansas and Oklahoma (Table 3).

Arkansas Portion ONF

During the four-year study 14 species of crayfishes contained within three genera were collected or documented from the Arkansas portion of the ONF. A total of 256 collections representing 2,337 individual crayfishes was made from the ONF in Arkansas. Arkansas has 53 species inhabiting the state, the most of any state west of the Mississippi River (Bouchard and Robison, 1980; Taylor et al., 1996). The 14 species documented from within the ONF in Arkansas represented 26.4 percent of the total crayfish fauna of Arkansas.

Table 4 provides the abundance of the 14 crayfish species documented from the Arkansas portion of the ONF during this study. Abundance was divided into four categories: abundant, common, uncommon, and rare. A species was considered rare if two or fewer collections were made. If 3-10 collections were made of the species, it was considered uncommon, while 11-20 collections provided a species with a designation of common. If a species was collected more than 20 times it was considered abundant. These designations are not meant to imply overall conservation status, but rather simply to provide the reader with some idea of what to expect regarding the abundance of these crayfishes on the ONF.

The two most abundant crayfish species within the streams and rivers of the Arkansas portion of the ONF were Orconectes acares which was collected 129 times with 1,258 individual specimens taken while Orconectes palmeri longimanus was taken 115 times with 807 specimens resulting (Table 4). In terms of abundance frequency, 53.83 percent of the total crayfishes collected were Orconectes acares while 34.53 percent were Orconectes palmeri longimanus (Table 4). Both crayfish species occurred in almost half of all collections made from lotic situations within the Arkansas portion of the ONF.

Orconectes leptogonopodus was considered common on the Arkansas portion of the ONF while Fallicambarus harpi, Orconectes sp. nov., Procambarus acutus, P. reimeri were deemed uncommon (Table 4). Rarely taken from the Arkansas portion of the ONF were Orconectes menae, Fallicambarus jeanae, Fallicambarus strawni, Procambarus liberorum, P. ouachitae, and P. tenuis (Table 4). Although not collected during this study, Procambarus parasimulans was considered rare on the ONF in Arkansas having been collected only once years ago by Dr. Pat Blair, University of Tulsa from near Caddo Gap and identified by the late Dr. Horton H. Hobbs of the Smithsonian Institution.

Crayfish habitat for lotic species such as Orconectes palmeri longimanus, and O. acares is quite abundant on the ONF in Arkansas and a large number of individuals of each species was collected by lifting large flat rocks lying in the stream or at stream margins or by seining swift flowing shoal areas. Headwater areas of all ONF streams had abundant crayfish habitat and crayfishes were common at most places searched.

In addition to the vast lotic habitat on the Arkansas portion of the ONF, a relatively large amount of lentic habitat occurs within the Ouachita National Forest from both natural and man-made sources. Lake Winona, Iron Fork Lake, and of course Lake Ouachita are some examples of man-made lentic environments.

Other lentic bodies of water include a number of Forest Service ponds constructed as wildlife watering areas which are available as crayfish habitat with species such as Orconectes palmeri longimanus proving extremely abundant in some of these.

Burrowing habitat in the form of seepage areas, fields, and roadside ditches is rather abundant throughout the Arkansas portion of the ONF in addition to the numerous seeps and spring areas. The ONF in Arkansas lies in the heart of the distributions of some of the most interesting burrowing crayfishes. Although generally uncommon except in certain specific habitats and at precise times of the year, primary burrowers of the ONF were Fallicambarus strawni, F. harpi, F. jeanae, Procambarus liberorum, P. parasimulans, and P. reimeri.

Distributionally, the greatest diversity in crayfish species occurred in the Ouachita River drainage (Table 5), as eight species were collected within its confines. The Little Missouri River drainage yielded five species while three species were taken from the Caddo River, Poteau River, and Fourche la Fave River (Table 5).

Oklahoma Portion ONF

During the four-year study eight species of crayfishes within four genera were collected or documented from the ONF in Oklahoma. A total of 204 collections representing 1,192 individual crayfishes was made from the ONF in Oklahoma. Oklahoma has 23 species living within its borders (Taylor et al., 1996). Although only eight species in four genera were documented from the Oklahoma portion of the ONF, this figure represents 34.8 percent of the total crayfish fauna of Oklahoma.

Table 6 provides the abundance of the eight crayfish species documented from the Oklahoma ONF during this study. Just as with the Arkansas portion of the ONF, abundance for the Oklahoma portion of the ONF was divided into four categories: abundant, common, uncommon, and rare. A species was considered rare if two or fewer collections were made. If 3-10 collections were made of the species, it was considered uncommon while 11-20 collections provided a species with a designation of common. If a species was collected more than 20 times it was considered abundant. These designations are not meant to imply overall conservation status, but rather simply to provide the reader with some idea of what to expect regarding the abundance of these crayfishes on the Oklahoma ONF.

One species dominated the crayfish fauna of the ONF in Oklahoma. That species was Orconectes palmeri longimanus (Table 6). A total of 158 collections of Orconectes palmeri longimanus was made in the Oklahoma portion of the ONF which resulted in 1,041 individuals being taken (Table 6). In terms of abundance frequency, an astounding 87.33 percent of the total crayfishes collected during the study in Oklahoma were Orconectes palmeri longimanus (Table 6). This species was collected in 87.29 percent of all collections made from aquatic habitats within the ONF in Oklahoma.

Procambarus acutus was collected 20 times (58 individuals) and Orconectes leptogonopodus was taken 12 times (54 specimens) rendering both species to be considered common on the ONF in Oklahoma, while Fallicambarus fodiens (six times), Faxonella blairi (five times), and Procambarus curdi (three times) were deemed uncommon (Table 6). Rarely taken (only twice collected) from the ONF in Oklahoma was Procambarus tenuis (Table 6). Although not collected during this study, Orconectes saxatilis is considered the rarest crayfish on the ONF in Oklahoma.

Crayfish habitat for lotic species such as Orconectes palmeri longimanus, and O. leptogonopodus is abundant on the ONF in Oklahoma and each species was collected by lifting large flat rocks lying in the stream or at stream margins or by seining swift flowing shoal areas. Headwater areas of all ONF streams in Oklahoma had abundant crayfish habitat and crayfishes were common at most places searched.

In addition to lotic habitat, a limited amount of lentic habitat occurs within the ONF in Oklahoma from both natural and man-made sources. Cedar Lake in LeFlore County and Ward Lake in McCurtain County are good examples of larger lentic habitat within the ONF boundaries. Within the ONF are also Forest Service ponds constructed as wildlife watering areas which are available as crayfish habitat with species such as Procambarus acutus and Orconectes palmeri longimanus often reaching large numbers.

Burrowing habitat in the form of pasture, abandoned fields, roadside ditches and other low-lying seepage areas is abundant in some areas of the ONF in Oklahoma, particularly in the Tiak District. Primary burrowers such as Fallicambarus fodiens, Procambarus curdi, Faxonella blairi, and even secondary burrowers such as Procambarus acutus and Orconectes palmeri longimanus utilize these abundant habitats within the ONF.

Distributionally, the greatest diversity in crayfish species in the Oklahoma portion of the ONF occurred in the Little River system (Table 7), where six species were collected within its defined watershed. The Kiamichi River system provided habitat for four crayfish species while three species were taken from the Mountain Fork River and two crayfish species each were from the Glover and Poteau River, respectively (Table 7).

CONSERVATION STATUS OF FOREST CRAYFISHES

Taylor et al., (1996) recently published a comprehensive report of the conservation status of the crayfishes of the United States and Canada. This inclusive document provided by the seven member American Fisheries Society (AFS) Endangered Species Committee (of which the Principal Investigator was a member) is the first attempt to provide a conservation status for all 338 crayfish species occurring within the United States and Canada for use by resource managers, lawmakers, citizens, and aquatic biologists alike.

Table 8 presents the conservation status of each of the 18 crayfish species collected on the ONF in Arkansas and Oklahoma as given by Taylor et al., (1996). Regarding crayfish species inhabiting the ONF, Orconectes saxatilis, Fallicambarus harpi, and Procambarus reimeri were considered "Endangered" while Fallicambarus strawni and Orconectes menae were given a conservation status of "Threatened" (Taylor et al., (1996). Fallicambarus jeanae and Procambarus tenuis were designated a conservation status of "Special Concern" which is a species that may become endangered or threatened by relatively minor disturbances to its habitat and deserves careful monitoring of its abundance and distribution (Table 8). Ten of the other crayfish species documented on the Ouachita National Forest in Arkansas and Oklahoma were "Currently Stable." A single, as yet undescribed crayfish species, Orconectes sp. nov., collected on the ONF in Arkansas was not considered by Taylor et al., (1996).

The most endangered crayfish species on either the Oklahoma or Arkansas portions of the Ouachita National Forest obviously is Orconectes saxatilis. This crayfish species has only been collected once by Bouchard and Bouchard (1976) from Pigeon Creek, LeFlore County, Oklahoma. It was not taken during this survey, although three separate trips were made to the type locality specifically to collect this crayfish. It is recommended that a separate Challenge Cost-Share be immediately initiated to study this crayfish for the entire year and specifically in the area of the type locality in an effort to document if it still exists.

Procambarus reimeri seems to be in better shape with regard to its conservation status of endangered. It is fairly common in specific areas near Mena, Polk County, Arkansas, but should be monitored carefully in the future.

A recent report by Robison (2000) considers Fallicambarus harpi to be a species of "Special Concern" as it was found to be much more common and widespread than formerly believed.

With regard to the two crayfish species considered "Threatened," Fallicambarus strawni and Orconectes menae should be monitored closely in the future to determine any possible trends.

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