Little Chucky

chucky madtom (Noturus crypticus)
Photo credit: Conservation Fisheries Inc.

Madtoms are small members of the Catfish Family (Ictaluridae) and have one of the most interesting names of all freshwater fishes. The name "madtom" comes from the fish's erratic swimming behavior when captured (Jordan 1889, Ono 1983) and possibly from its unique self defense mechanisms. Indeed, these small secretive catfish are well armed with fused dorsal rays, or "barbs," that can inflict a painful puncture wound to the unwary handler. Madtoms, despite their small size, can be distinguished from other freshwater catfish because their caudal or "tail" fins merge with their adipose (fleshy) fins.

Many species of madtoms have drawn the attention of conservation groups and resource agencies in recent years due to their scarcity. The chucky madtom (Noturus crypticus) is a recently described species known from only 15 specimens collected from two Tennessee streams: Dunn Creek in Sevier County, Tennessee, and Little Chucky Creek in Greene County, Tennessee (Burr et al. 2005). Only three chucky madtoms have been encountered since 1994 despite many surveys of both streams and other streams in eastern Tennessee of similar size and character. The chucky madtom is obviously a very rare fish.

Not much is known about chucky madtom life history, but useful information on feeding and breeding behavior can be gleaned from literature on closely related madtoms (Etnier and Jenkins 1980, Burr and Dimmick 1981, Dinkins and Shute 1996). Madtoms are nocturnal and usually well hidden during the day. Many species of madtoms are benthic (i.e., bottom dwelling) fishes that hide under gravel, sand, leaves, and logs to avoid detection from predators. Madtom diets consist primarily of small aquatic insects, some populations of which are sensitive to degraded water quality. The combination of life spans typically less than three years and low reproductive capacity compared to other North American fishes leaves madtom populations vulnerable to environmental disturbances that could disrupt spawning in even a single year. These life history traits contribute to the relatively high degree of imperilment in madtoms as a group (Warren et al. 1997).

All of the chucky madtoms known to science have been found in stream runs with slow current over gravel and bedrock (Burr and Eisenhour 1994). The areas where this species is known to exist have intact streamside vegetation (Shute et al. 1997), suggesting the importance of riparian buffers for maintaining habitat quality in aquatic systems.

Because of its extreme rarity and the threat of extinction, the U.S. Fish and Wildlife Service declared the chucky madtom a candidate for protection under the Endangered Species Act in 2002 (U.S. Fish and Wildlife Service 2002) . The species is currently listed as "endangered" by the State of Tennessee.

Order: Siluriformes (catfish)
Class: Actinopterygii (ray-finned fishes)
FishBase name: Chucky madtom
Max. size: 6.5 cm SL (male/unsexed; Ref. 56218)
Environment: benthopelagic; freshwater
Climate: tropical
Resilience: High, minimum population doubling time less than 15 months(Preliminary K or Fecundity.)
Distribution: Gazetteer North America: USA.
Morphology: Dorsal soft rays (total): 6 - 6; Anal soft rays: 15 – 17. Diagnosis: Distinguished from other members of the Noturus elegans species group by having: modally 16 anal rays (vs. 18 in Noturus fasciatus); modally 8 pelvic rays (vs. 9); 2-10 medium-large sized melanophores on the cheek (vs. large melanophores absent on cheek); adipose fin band extending only to base or half-way up fin (vs. extending half-way up to edge of fin in fasciatus); adipose and caudal fins distinctly joined at their juncture (vs. weakly connected in fasciatus); three evenly spaced pale and dark bands in caudal fin (vs. caudal fin bands usually two and unevenly spaced); robust body shape, with body width at pectoral fin origin 23% or more of SL and greater than anal fin base length (vs. slender body shape, with body width at pectoral fin origin 22% or less of SL and less than anal fin base length). There is an absence of shared alleles for eight allozyme loci (mAAT-A, sACOHA, GPI-B, LDH-B, sMDHP-A, Pep-b, Pep-D, and PGM-A) distinguishes crypticus and fasciatus, which also differ by 5% Cytb sequence divergence. Similarly, both share no alleles at eight allozyme loci (mAAT-A, sAATA-A, sACOH-A, FUM-A, GPI-A, GPI-b, LDH-B, sMDHP-A, and Pep-D) and are 6.3% divergent for Cytb (Ref. 56218).
Red List Status: Not in IUCN Red List (Ref. 53964)
Dangerous: harmless

STATUS:
On June 14, 1976, the Cumberland bean pearlymussel was designated as endangered throughout its entire range, except where listed as experimental populations (USFWS 1993). Within the area covered by this listing, this species is known to occur in Kentucky and Tennessee. On June 14, 2001, the Cumberland bean pearlymussel was designated as experimental population, non-essential in Alabama (the free-flowing reach of the Tennessee River from the base of the Wilson Dam downstream to the backwaters of Pickwick Reservoir and the lower five reach miles of all tributaries to this reach in Colbert and Lauderdale Counties. A recovery plan for the species was approved August 22, 1984 (USFWS 1984).

SPECIES DESCRIPTION:
The Cumberland bean pearlymussel is a small to medium sized freshwater mussel with relatively thick, elongated, oval shells. The shells of the females are somewhat more rounded and slightly larger (maximum about 55 millimeters or 2.2 inches long) (Parmalee and Bogan 1998; USFWS 1984). Like other freshwater mussels, the Cumberland bean pearlymussel feeds by filtering food particles from the water column. The specific food habits of the species are unknown, but other juvenile and adult freshwater mussels have been documented to feed on detritus, diatoms, phytoplankton, and zooplankton (Churchill and Lewis 1924). The diet of Cumberland bean pearlymussel glochidia, like other freshwater mussels, comprises water (until encysted on a fish host) and fish body fluids (once encysted).

REPRODUCTION AND DEVELOPMENT:
The reproductive cycle of the Cumberland bean pearlymussel is similar to that of other native freshwater mussels. Males release sperm into the water column; the sperm are then taken in by the females through their siphons during feeding and respiration. The females retain the fertilized eggs in their gills until the larvae (glochidia) fully develop. The mussel glochidia are released into the water, and within a few days they must attach to the appropriate species of fish, which they parasitize for a short time while they develop into juvenile mussels. They then detach from their fish host and sink to the stream bottom or other substrate where they continue to develop, provided they land in a suitable substratum with the correct water conditions. Spawning likely occur in late summer through early fall; the glochidia are likely released in late spring and early summer (Schultz 1996). Two fish have been identified as glochidial hosts, the fantail darter (Etheostoma flabellare) and striped darter (Etheostoma virgatum) (Layzer and Madison 1995).

RANGE AND POPULATION LEVEL:
The Cumberland bean pearlymussel was historically known from ten river systems in the Cumberland and Tennessee river basins in Alabama, Georgia, Kentucky, Tennessee, and Virginia (USFWS 1984). The Cumberland bean currently survives only in the Hiwassee River in Tennessee and in Buck Creek, the Little South Fork of the Cumberland River, and the Rockcastle River system in Kentucky (USFWS 2001). A relatively strong population still exists in a short reach of the Hiwassee River downstream of the North Carolina/Tennessee State line in Polk County, Tennessee (Parmalee and Bogan 1998). Although no specimens have been collected in North Carolina, the habitat appears suitable, and it is likely that the species occurs in small numbers in the North Carolina portion of the Hiwassee River below Appalachia Dam, Cherokee County (J. Fridell, USFWS, personal communication 2000).

HABITAT:
The Cumberland bean pearlymussel inhabits small rivers and streams in fast riffles with gravel or sand and gravel substrate. Individuals have been found in riffle and run habitat areas with shallow water depths (less than one meter) and clean, stable substrate. Individuals can often be found in transitional zones between sand and gravel substrates (USFWS 1984; Clark 1981; NatureServe 2003).

PAST THREATS:
The Cumberland bean pearlymussel has been directly impacted by impoundments, siltation, channelization, and water pollution. Reservoir construction is the most obvious cause of the loss of mussel diversity in the basin's larger rivers. Most of the main stem of both the Tennessee and Cumberland River and many of their tributaries are impounded. For example, over 2,300 river miles or about 20 percent of the Tennessee River and its tributaries with drainage areas of 25 square miles or greater are impounded (Tennessee Valley Authority 1971). In addition to the loss of riverine habitat within impoundments, most impoundments also seriously alter downstream aquatic habitat; and mussel populations upstream of reservoirs may be adversely affected by changes in the fish fauna essential to a mussel's reproductive cycle (USFWS 2003). Coal mining related siltation and associated toxic runoff have adversely impacted many stream reaches. Numerous streams have experienced mussel and fish kills from toxic chemical spills, and poor land use practices have fouled many waters with silt. Runoff from urban areas has degraded water and substrate quality. Because of the extent of habitat destruction, the overall aquatic faunal diversity in many of the basins' rivers has declined significantly (USFWS 1984).

CURRENT THREATS:
The low number of individuals and the restricted range of each of the surviving populations make them extremely vulnerable to extirpation from a single catastrophic event or activity, such as a toxic chemical spill or major channel alteration. Pollutant threats to freshwater mussels are well documented in the general mussel description.

CONSERVATION MEASURES:
Objectives in the recovery plan call for: (1) restoring the viability of its populations in Buck Creek, the Rockcastle River, and the Little South Fork River in Kentucky (at the time the recovery plan was written, we did not know that a population still existed in the Hiwassee River); (2) reestablishing or discovering viable populations in two additional rivers; and (3) ensuring that there are no foreseeable threats to the continued existence of any of the populations. Currently, artificial propagation and reintroduction technologies for this and other federally listed mussels are being developed. Other potential conservation measures include reintroducing the Cumberland bean into historic habitats in two reaches in the Tennessee River basin (USFWS 1984).