Tuesday, April 18, 2017

A Rare Peek at Clinch Dace Spawning, by Don Orth

Today, The American Midland Naturalist released a paper on spawning observations of Clinch Dace (Chrosomus sp. cf. saylori). Clinch Dace is a species of high conservation need due to a restricted distribution, low population densities, and modified stream habitats.  Clinch Dace occur in only 31.5 km of headwater streams and the global population size is below 10,000 individuals (Moore et al. 2017). Ten of these areas have abandoned mine sites with $12.5M in unfunded restoration costs.  Restoration of the streams will take decades, but in the meantime, we must characterize and protect the remaining genetic diversity.

Several years ago, Hunter Hatcher and Michael Moore noted that the Clinch Dace in standardized samples were becoming more colored up each day.  They literally stumbled across a small depression in a creek where they witnessed numerous Clinch Dace in breeding coloration.  In these small streams, small circular pits are created by Creek Chubs and Stonerollers.     
Clinch Dace.  Photo by Isaac Szabo
In the midst of a busy field schedule, they managed to capture videos over a three-day period. These observations provide a rare peek into the behavior of this small, rare fish.   Since so little is known about the Clinch Dace, any observations could prove helpful and may assist with future captive propagation efforts (Rakes et al. 2013).  A short portion of the hours of video obtained may be viewed by clicking here.

After the field season, Hunter and Michael watched the videos over and over again, taking notes, making observations, and asking more questions.  The behaviors of the Clinch Dace changed each day.  Hatcher et al. (2017)  speculated that the early behaviors were territorial pre-spawn behaviors.  The Clinch Dace were so brightly colored that it seemed that spawning would soon be underway.   Water temperature (21.8 C) was higher than observed by White and Orth (2014) in the only other field observation of the Clinch Dace spawning behavior.  Many behaviors were characterized, including the behaviors that include females being corralled and clasped by males.  Though gamete release was not confirmed from video observations, the videos likely bracketed actual breeding events.  

Habitat is an important determinant of nest location in other fine-scaled daces Chrosomus.  Other species of Chrosomus exhibit flexibility in type of nest used.  For the  blackside dace (Chrosomus cumberlandensis), a federally listed threatened species,  flow and depth were the most influential factors in determining nest location and nest activity, respectively, and nest activity was positively correlated with substrate size (Scherer et al. 2014).

The rare observation is important because it indicates that Clinch Dace are breeding.  Although the numbers of breeders was small, the aggregation behaviors appeared to be similar to that observed in other Chrosomus dace.   If they are unable to find suitable mates due to low population densities, reproductive isolating mechanisms may break down.   In one stream, a hybrid between Clinch Dace and Rosyside Dace.
Top: Clinch Dace. Middle: hybrid Clinch Dace x Rosyside Dace. Bottom: Rosyside Dace.   Photo by Michael J. Moore.
The first step in science is observation. This rare peek raises many questions. The questions asked and what comes next is up to us. I hope the future brings efforts to spawn and propagate the Clinch Dace in captivity to enhance small populations and restore populations to some stream segments.

Hatcher, H.R., M.J. Moore, and D.J. Orth. 2017.  Spawning observations of Clinch Dace: Comparison of Chrosomus spawning behavior.  The American Midland Naturalist 177:318-326.     
Rakes, P.L., M.A. Petty, J.R. Shute, C.L. Ruble, and H.R. Mattingly. 2013. Spawning and captive propagation of Blackside Dace, Chrosomus cumberlandensis. Southeastern Naturalist 12(Special issue 4): 162-170 .
White, S. L., and D. J. Orth. 2014. Reproductive biology of Clinch Dace, Chrosomus sp. cf. saylori. Southeastern Naturalist 13(4): 735-743.

Wednesday, April 12, 2017

Mad About Madtoms, by Don Orth

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.
Cute Margined Madtom Noturus insignis Photo by D.J.Orth 
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.
Mountain Madtom Noturus eleutherus have a highly fragmented distribution.   photo by Tim Lane 
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.
Life is precarious for the madtoms because many species have very small distributions.  Seldom are populations abundant.   Fourteen of the 29 species are threatened, endangered, or under review by the U.S. Fish and Wildlife Service.  The Smoky Madtom N. baileyi, Chucky Madtom N. crypticus, and Pygmy Madtom N. stanauli are endangered.  Yellowfin Madtom N. flavipinnis and Neosho Madtom N. placidus are threatened. Carolina Madtom N. furiosus, Orangefin Madtom N. gilberti, Piebald Madtom N. gladiator, Ouachita Madtom N. lachneri, Freckledbelly Madtom N. minitus, and Caddo Madtom N. taylori are under review. One species, the Scioto Madtom N.trautmani, is endangered but, in fact, may be extinct (Platt 2013).  

Pygmy Madtoms only reach 50 mm whereas the widespread Stonecat N. flavus may exceed 300 mm.  Smoky Madtoms Noturus baileyi have a 2-year life span and only attain 73 mm. These tiny madtoms are associated with silt-free riffle habitats and frequently associate with cobble-size slab rocks for concealment during daylight.  They feed at night on immature aquatic insects. In winter, madtoms inhabit pools.  Yellowfin Madtoms are often found concealed beneath cobbles or undercut banks, or hidden in leaf litter (Gibbs et al. 2014). They have a longer life span (3 to 4 years) and attain a larger size (134 mm). 
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.
Yellowfin Madtom Recovery shirt   Photo by David Crigger, Bristol Herald Courier. 
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/ on April 10, 2017.
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. 

Friday, April 7, 2017

Painful Stings of the Notorious Noturus, by Don Orth

Nothing is cuter than a baby madtom (genus Noturus).  When you encounter a little madtom you will learn that they are impossible to handle.  It is best to scoop them into a container of river water.  Watch. Don’t touch!   The madtom catfishes are notorious for the painful stings they deliver. Experienced folks will tell you to wipe the wound with the madtom slime. If the tiny madtom escapes before you slime the wound, there is not much to do to relieve the pain.  Is there anti-venom in catfish slime?  Who knows.  But I do know this pain is vastly out of proportion to the tiny prick wound. The madtom toxin surely knows how to excite your nocireceptors (pain receptors).
How cute is this Margined Madtom Noturus insignis   Photo by D.J. Orth.
Madtoms represent an unsolved paradox -- popular baitfish combined with a powerful anti-predator device. Many years ago, I remember we were examining Smallmouth Bass for internal and external health assessments. At one sample site, we encountered many Smallmouth Bass with numerous perforations in the stomachs.  A closer look revealed fish spines.  An even closer look indicated they were madtom spines.  Smallmouth Bass here were frequently feeding on madtoms and the spines were archived in the stomachs.  We never observed this at other sites. Why is a venomous fish so highly preferred by hungry Smallmouth Bass and Walleye? 

Many lineages of fishes produce venom. The venom apparatus of all venomous fish consists of the same basic structure—a spine, associated with venom secreting cells, all covered in an integumentary sheath. When the spine pierces tissue and the sheath ruptured, the venom is released.  The catfishes, Siluriformes, have over 1,250 venomous species (Wright 2012); perhaps, half of all venomous fish are catfish!  Unlike crinotoxins in some reptiles and Stonefish (Synanceia trachynis), which are poisonous when touched or eaten, the catfish inject the venom with their sharp dorsal and pectoral spines.    In this dorsal view of Noturus gladiator you can see just how effective these spines can be in delivering venom.
Dorsal view of Noturus gladiator.  Note how the extended pectoral spines almost triple the width of the madtom, thereby restricting ingestion by piscivores.  Photo by Egge and Simon (2011).
When injected into the musculature of another fish, the venom results in rapid color loss, edema, hemorrhage, reduced mobility, loss of equilibrium, and even mortality; the response depends on dosage (Birkhead 1972; Wright 2012).  Few controlled studies examine the effects or compare catfish venom toxicity.  However, we assume that the madtom catfishes use their venomous spines as one of several anti-predator strategies.  Other madtom anti-predator strategies include nocturnal activity, camouflage via disruptive coloration, and benthic hiding (Armbruster and Page 1996).  

Madtoms are popular baits for walleye and bass.  Most anglers catch them and some bait shops sell them.  “Willow cats” are Tadpole Madtoms Noturus gyrinus, and were historically used as walleye baits in the upper Mississippi (Cochran 2011).   “Sometimes a dozen will fetch $15 or more during Walleye tournaments (Schmitt 2012).  Madtoms, also called stonecats, are especially effective live baits for Smallmouth Bass.  Margined madtom Noturus insignis are a preferred bass baitfish in the United States (Litvak and Mandrak 1993).  
Different spine morphologies in (A) Noturus gyrinus, (B) Noturus exilis, (C) Noturus miurus, and (D) Noturus stigmosus.   Photo by Wright (2012).
The spines of catfish deliver the venom and differ in morphology.  Pectoral spines are highly variable among species, whereas the dorsal spines are generally similar among species.  Some have a smooth spine, which may or may not possess a venom gland.  Some spines have serrations.   Venom glands may be associated with the shaft of the spine or the serrations.   Serrated pectoral spine with a venom gland is the ancestral condition for the genus.
Sagittal section of a madtom spine and venon gland.  e, epidermis; gr, grooves;  
s, spine shaft; vg, venom gland   Photo from Egge and Simon (2011).
More Noturus have serrations on pectoral spines.  Serrations likely increase damage caused by the sting, and facilitate the entry of venom into the wound.   This explains why some madtom stings are worse than others.  Yes, I know many fish biologists that have stung themselves with different madtom spines to verify this fact.  Not me.  I am venom phobic. It is unclear why some species of catfish do not have venom glands or if venom composition varies among species (Egge and Simon 2011).  We know they certainly hurt humans (McKinstry 1993).

The predominance of venom glands in Noturus suggests a vital anti-predator defense in these small catfish.  Several investigators examined the anti-predator hypothesis and supported what anglers already knew. Piscivores, such as black bass Micropterus spp., love to eat madtoms.  
The spines function against a gape-limited predator by increasing the difficulty of ingestion.   But spines do not deter capture, but if spines are clipped the small catfish are even more likely to be eaten (Emmet and Cochran 2010; Wright 2012).   You must remember that there are many species of catfish that co-evolved with the piscine predators.  Not all catfish have the same venom toxicity.  Wright (2012) discovered that the venom of the Tadpole Madtom was more noxious than that of the Yellow Bullhead Ameirus natalis.   It is unlikely that the hungry Walleye would be able to distinguish the difference between these species.   So they attack, capture, and deal with the consequences.   Emmet and Cochran (2011, p. 477) reported “no apparent long term negative effects were displayed by bass following interactions with madtoms.”  The other line of evidence that supports the anti-predator hypothesis is the observation that in the absence of predation pressure over many generations, domestic catfish show reduced spine size (Fine et al. 2014).
Comparison of attacks per hour and handling time (min) of Largemouth Bass for intact, stripped (of venom), and spine-removed Tadpole Madtom.  Yellow Bullhead (Amieurus natalis) and Bullhead Minnow (Pimelphales vigilax) were also tested.   From Wright (2012).
The question still remains “Why do bass and walleye like madtoms?”  We don’t know.  Maybe it's the same reason we like red hot chili peppers and the capsaicin burnMaybe it’s because madtoms are just so cute.  Much more can be learned about madtom venoms.   Very few catfish venoms have been studied in detail to explore diversity of venoms among catfishes (Wright 2017). The venom glands are evolutionarily derived from epidermal secretory cells.  However, scientists are still uncertain as to whether the venoms are derivatives of crinotoxins or healing and antimicrobial substances produced by epidermal cells. The bioactive components of venoms in fishes is a largely unexplored source of new pharmaceuticals (Sivan 2009).  

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.
Birkhead, W.S. 1972. Toxicity of stings of ariid and ictalurid catfishes. Copeia 1972:790-807.
Cochran, P.A. 2011. Back to the fifties: Historical use of “Willow Cats” as bait in the upper Mississippi River valley. Pages 305-311 in P.H. Michaletz and V.H. Travnichek, editors.  Conservation, ecology, and management of catfish: the second international symposium.  American Fisheries Society Symposium 77, Bethesda, Maryland
Egge, J.J.D., and A.M. Simons. 2011.  Evolution of venom delivery structures in madtom catfishes (Siluriformes: Ictaluridae).  Biological Journal of the Linnean Society 102:115-129.
Emmett, B., and P. A. Cochran. 2010. The Response of a piscivore (Micropterus salmoides) to a venomous prey species (Noturus gyrinus), Journal of Freshwater Ecology 25:475-479  DOI: 10.1080/02705060.2010.9664391
Fine, M.L., S. Lahiri, A.D.H. Sullivan, M. Mayo, S.H. Newton, and E.N. Sismour. 2014. Reduction of the pectoral spine and girdle in domesticated catfish is likely caused by changes in selective pressure. Evolution 68:2102-2107.  DOI: 10.1111/evo.12379
McKinstry, D.M. 1993.  Catfish stings in the United States: case report and review.  Journal of Wilderness Medicine 4:293-303.
Litvak, M.K., and N.E. Mandrak. 1993. Ecology of freshwater baitfish use in Canada and the United States. Fisheries 18(12):6-13.
Schmitt, K. 2012. NANFA members search for Minnesota’s rarest fishes.  American Currents 37(4):2-14.  
Sivan, G. 2009.  Fish venom: pharmacological features and biological significance.  Fish and Fisheries 10:159-172.
Wright, J.J. 2012.  Adaptive significance of venom glands in the tadpole madtom Noturus gyrinus (Siluriformes: Ictaluridae). The Journal of Experimental Biology 215:816-1823
Wright, J.J. 2017.  Evolutionary History of Venom Glands in the Siluriformes. Pages 279-301 in P. Gopalakrishnakone, and A. Malhotra, Editors.  Evolution of Venomous Animals and Their Toxins.  Toxinology.  Springer.  DOI 10.1007/978-94-007-6458-3_9