In my last blog post, I explored the paradox of the popular, though venomous, little madtom (genus Noturus). But there is more to the madtom story than that painful sting. Madtoms are cryptic species in more ways than one. Many species are at risk of extinction, but there is reason to be hopeful for recovery. Reintroduction and stream and watershed restoration may someday return Mad Tom to their historical homes. And yea! They are also the cutest little catfish.
There are currently 29 species of Noturus madtoms. Madtoms originated sometime in the middle Miocene (Arce-H et al. 2016) and occur in streams of eastern North American. Madtoms resemble small bullheads, but they have a long adipose fin that is joined to a rounded caudal fin. For a gallery of my favorite madtom photos (how many people have a madtom gallery?) click here.
Madtoms are nocturnal benthic hiders that are colored to blend into the environment during the daytime. While many madtoms are uniformly colored to match their surroundings, others achieve crypsis through disruptive coloration. Light spaces between the dark saddles mimic rocks and dark saddles mimic shadows between rocks (Armbruster and Page 1996). One good example is the Piebald Madtom Noturus gladiator.
|The boldly contrasting dark saddles on the yellow-tan back and side serve to camouflage the Piebald Madtom Noturus gladiator. Dorsal view (top) and lateral view (bottom) Photos by M.R. Thomas from Egge and Simons (2011)|
Madtoms are cryptic in another sense. Pigmentation is a common distinguishing character, but pigment pattern can vary depending on the environment. There are very subtle differences among cryptic species. Different species are so similar in morphology and color pattern as to be nearly indistinguishable. For example, the Piebald Madtom was formerly considered to be a Northern Madtom Noturus stigmosus (Thomas and Burr 2004). The Chucky Madtom N. crypticus and Saddled Madtom N. fasciatus were formerly considered to be part of the Elegant Madtom Noturus elegans complex (Burr et al. 2005; Near and Hardman 2006). Finally, the Black River Madtom N. maydeni was formerly the Ozark Madtom N. albater (Egge and Simon 2006). More new madtoms are likely to be described.
|Cryptic species of Noturus. Black River Madtom (top) was recently described from a portion of the range of the Ozark Madtom (bottom). Photos by Uland Thomas|
Both conventional sampling and underwater observations have low detection rates for madtoms (Davis et al. 2011). While sampling fishes in southeast Oklahoma, I employed a three-pass removal method for estimating fish population size. The Freckled Madtom Noturus nocturnus seldom met the requirements of the method. First pass I might get 3 madtoms, followed by 6 in pass two, and 10 or more in pass three. The math didn’t work out because I assumed the probability of catching a Freckled Madtom was equal in each pass. However, direct current electrofishing distressed madtoms each time and they moved up through the hyporheic zone, making them more detectable on each subsequent pass.
Madtoms, like many catfishes, are nocturnally active and use different habitats between night and day. Their habitat varies greatly among different species but many occur in small streams and require loose cobbles or woody debris for cover. Madtoms are small and feed on immature aquatic insects. We cannot assume that all madtoms have similar habitat use patterns. Low detection rates means we may often overlook important habitats for these little catfishes.
|The aptly named Pygmy Madtom (top) attains an adult size of only 50 mm. The Stonecat may reach 12 inches (300 mm). Top photo by Conservation Fisheries, Inc. Bottom by Kentucky Fish and Wildlife.|
Rarity, small distributions, and low detectability make monitoring and inventorying the madtoms very difficult. For decades, the Yellowfin Madtom and Smoky Madtom were presumed extinct. The Yellowfin Madtom was not collected anywhere between 1893 and 1968 (Etnier 1994). The Smoky Madtoms were known only from Abrams Creek in Tennessee. However, a stream reclamation project in 1957 killed all fishes in Abrams Creek so that Brook Trout could be restored. Fortunately, the Smoky Madtom was rediscovered in adjacent Citico Creek in 1980. Many years of captive propagation, pioneered by Conservation Fisheries, Inc., and stocking have restored breeding populations of both madtoms (Shute et al. 2005).
This first success at madtom recovery has led to other efforts to reintroduce the Yellowfin Madtom to historic habitats in Nork Fork Holston River and Powell and Clinch Rivers. Given the small ranges of many madtoms, the threats vary greatly among the various at-risk species. Where channelization has straightened and simplified streams, artificial riffle construction has been implemented (Fuselier and Edds 1995), whereas other locations minimum flow releases from dams were increased (Wildhaber et al. 2000). There are reasons to hope that madtom recovery efforts may be more commonplace in the future.
Arce-H., M., J.G. Lundberg, and M.A. O’Leary. 2016. Phylogeny of the North American catfish family Ictaluridae (Teleostei: Siluriformes) combining morphology, genes and fossils. Cladistics 2016:1-23. DOI: 10.1111/cla.12175
Armbruster, J.W., and L.M. Page. 1996. Convergence of a cryptic saddle pattern in benthic freshwater fishes. Environmental Biology of Fishes 45:249-257.
Burr, B. M., D. J. Eisenhour, and J.M. Grady. 2005. Two new species of Noturus (Siluriformes: Ictaluridae) from the Tennessee River Drainage: description, distribution, and conservation status. Copeia 2005:783–802.
Davis, J.G., J.E. Miller, M.S. Billings, W.K. Gibbs, and S.B. Cook. 2011. Capture efficiency of underwater observation protocols for three imperiled fishes. Southeastern Naturalist 10(1):155-166. DOI: http://dx.doi.org/10.1656/058.010.0113
Egge, J.J.D., and A.M. Simon. 2006. The challenge of truly cryptic diversity: diagnosis and description of a new madtom catfish (Ictaluridae: Noturus). Zoologica Scripta 35:581-595.
Etnier, D.A. 1994. Our southeastern fishes – What have we lost and what are we likely to lose. Proceedings of the Southeastern Fishes Council 29:5-9.
Fuselier, L., and D. Edds. 1995. An artificial riffle as restored habitat for the threatened Neosho Madtom. North American Journal of Fisheries Management 15:499-503
Gibbs,W.K., J. E. Miller, J. K. Throneberry, S. B. Cook, and M.A. Kulp. 2014. Summer habitat use and partitioning by two reintroduced rare madtom species. Journal of Freshwater Ecology 29:243-258. DOI: 10.1080/02705060.2014.881308
Near, T.J., and M. Hardman. 2006. Phylogenetic relationships of Noturus stanauli and N. crypticus (Siluriformes: Ictaluridae), two imperiled freshwater fish species from the Southeastern United States. Copeia 2006:378-383. DOI: http://dx.doi.org/10.1643/0045-8511(2006)2006[378:PRONSA]2.0.CO;2
Platt, J.R. 2013. Tiny Ohio catfish species, last seen in 1957, declared extinct. Scientific American Blog. Accessed at https://blogs.scientificamerican.com/extinction-countdown/tiny-ohio-catfish-species-last-seen-in-1957-declared-extinct/
Shute, J.R., P.L. Rakes, and P.W. Shute. 2005. Reintroduction of four imperiled fishes in Abrams Creek, Tennessee. Southeastern Naturalist 4:93–110.
Thomas, M. R. and B. M. Burr. 2004. Noturus gladiator, a new species of madtom (Siluriformes: Ictaluridae) from Coastal Plain streams of Tennessee and Mississippi. Ichthyological Exploration of Freshwaters 15:351–368.Wildhaber, M. L., and six coauthors. 2000. Ictalurid populations in relation to the presence of mainstem reservoir in a Midwestern warmwater stream with emphasis on the threatened Neosho Madtom. Transactions of the American Fisheries Society 129:1264-1280.