Mystery of the Black Blotched Bass, by Don Orth

Is there a Piscine Dermatologist anywhere?   If so, I need your expert assistance.  People post anomalous fish photos on Flickr, Facebook, Instagram, Pinterest, or Twitter all the time and ask “what is wrong with this fish?”   One mystery that has been around for a long time, and not yet solved is the mystery of the black blotched bass.     Too often all we have is the photos, which are insufficient for any diagnosis.

Smallmouth Bass with Melanosis, from Susquehanna River.  Photo by Bill Yingling

These bass have irregularly shaped black blotches on their bodies.    Largemouth Bass and Smallmouth Bass with these black blotches have been reported by anglers and by fisheries biologists alike.   These black blotches have been reported as early as 1980 from rivers, such as the Hudson and Susquehanna, as well as lakes, reservoirs, rivers and ponds in eastern, southern, and Gulf states.

What is it?    The black blotches are referred to as ‘melanosis’ or hyperpigmented melanosis.    Darkening is hyperpigmentation and lightening is hypopigmentation.    The normal coloration pattern that we observe is the result of genetics and the antagonistic reaction between the melanocyte-stimulating and melanin-concentrating hormones (Rakers et al. 2010).  

Fish skin, just like human skin, has an overlying epidermal layer and deeper dermal layer.  Pigment-holding cells are chromatophores and are named melanophores (melanin), iridophores (those that reflect light), or xanthophores (red, orange, and yellow).    Human skin gets its color primarily from melanin, a pigment produced by melanophores in the skin.  Melanophores in fish are equivalent in human skin.     Pigment patterns have a genetic basis and may also change rapidly in response to stress of a variety of sources.    This leads to short-term responses of patterns due to hormone levels -- for example some fish darken in response to social stresses due to interacting with other fishes in close quarters.     For a visual depiction of how rapidly coloration may change, click here to view the video of fish melanophores responding to adrenaline (Courtesy of Richard Wheeler RichardWheeler.net)

Melanosis is rare but has been reported in many types of fishes.     It is a stable pattern of pigmentation.   In humans a hyperpigmentation condition called melasma is sometimes referred to as "the mask of pregnancy," because it commonly appears on the faces of pregnant women, a response to hormone imbalances. 

Early papers described the condition from trout, salmon, and lungfish in large public aquaria (Nigrelli 1934; Smith and Coates 1936).  The lungfish melanosis resulted from “more or less prolonged or permanent expansion of melanophores, or from an actual increase in the melanophores of the skin,” whereas the trout and salmon was from paralysis of nerves controlling melanophores in the tail region.    Gordon (1931) developed a breeding protocol that resulted in melanosis in hybrid Platy x Swordtail fish.  This model system has been used in numerous early studies to investigate factors that may induce melanoma (Patton et al. 2010) and subsequent research on the Zebrafish (Danio rerio) model demonstrated that many of the genes that are involved in melanocyte development are the same genes that are mis-regulated in melanoma development.

Photo of hybrid female Swordtail crossed with a male Platy (Xiphophorus).  The male parent contributed the factor for macromelanophores and the female parent provided modifying factors that disturb normal development of pigment cells (Gordon 1931).  Photo: Texas State University.

What causes it?   Most of the observations by anglers and fisheries biologists have been bass 12 inches and larger, but this represents the size range that are typically encountered.   It is unclear whether black blotches are produced at birth at some later point in life in the fish caught by anglers. Fish have generalized responses to stresses and the normal skin melanization factors may be altered from pathogens, wounds, UV radiation, nutrition, stress, and environmental contaminants. 

Hyperpigmentation has been observed (though usually not the endpoint) in controlled toxicant exposure studies.     Exposures to dioxins resulted in hyperpigmentation in Zebrafish, Carp, and Largemouth Bass.     Because the black blotches are caused by multiple factors, we cannot derive a cause from symptom alone.   We could bring the fish to Dr. Don’s Piscine Dermatology Associates, if only it existed, to biopsy and examine affected tissues.    A thorough diagnosis would require a microscopic examination of the tissues to determine if there are cellular or tissue anomalies, pathogens, parasites, or simply higher levels of melanophores.

In seeking to understand, scientists hypothesize the sequence of conditions that might lead to black blotches and attempt to create black blotches in unaffected fish.   Perhaps an exposure to some unusual substance in water or diet leads to abnormal development and hormonal responses.  Or is it handling stresses during catch and release?    William L. Yingling, M.D., writing a comment to a blog post related to the Susquehanna River wrote “The increased frequency of these affected fish is not from better reporting.  Never saw this in the upper mainstem where I fish until 2010 and I've fished the same water since 1976. It is a new occurrence in these waters and it comes right on the heels of intersexing and bacterial infections that are killing the fish.”   Many black blotched bass reports emerge from the Susquehanna River where the fishery is in decline, yet “there is currently no voluntary or mandatory action plan to identify the causes and sources of the problem and find solutions (Arway and Smith  2013).”     In the New River, Virginia, where fisheries are thriving, fisheries biologists and anglers rarely encounter and report Smallmouth Bass with black blotches, and when they do it is only a few small blotches. 

Should the black blotched bass be a cause of our concern?        Should we be concerned about eating black blotched bass?   Most who have captured the bass with black blotches report that they appear to be actively feeding or otherwise in good condition.       The hyperpigmentation pattern represents a strange catch, but should not affect quality of flesh for human consumption.

One concern that remains is the changing environment.   Melanoma has been studied in laboratory investigations of Zebrafish and Platy x Swordtail hybrids and UV-B will induce melanoma in susceptible fish (Mitchell et al. 2010).       More recently, melanoma with patterns similar to UV-induced melanomas has been confirmed in Coral Trout Plectropomus leopardus at two sites in the Great Barrier Reef Marine Park (Sweet et al.  2012).     Increased UV affects wild animal populations in addition to humans!

Relevant and meaningful questions appear to be “Do these black blotched bass ever develop melanoma?”  “Does melanosis develop in response to acute handling stress and/or UV exposure during catch and release by anglers?” or “Are these melanotic bass produced at birth?”   or  “Is there something in the water?”  As bass fisheries have been effectively managed to permit longer-lived, trophy sized fish and more bass are caught and released, we certainly have older bass in our waters.    Humans, as we age, develop more dark spots for reasons that are not clear to us.  Are the black blotched bass associated with presence of many more old bass in our waters?      I am curious.

References

Arway, J.A., and G. Smith.  2013. The Susquehanna River-A fishery in decline. Fisheries 38(5):235-236.

Gordon, M.  1931.  Hereditary basis of melanosis in hybrid fishes.  American Journal of Cancer 15:1495-1523.

Kleeman, J.M, J.R. Olson, and R.E. Peterson.  1988.  Species differences in 2,3,7,8-tetrachlorodibenzo-p-dioxin toxicity and biotransformation in fish.  Fundamental and Applied Toxicology 10(2):206-213.

Mitchell, D. L. A. A. Fernandez, R. S. Nairn, R. Garcia, L. Paniker, D. Trono, H. D. Thames, I. Gimenez-Conti.  2010.  Ultraviolet A does not induce melanomas in a Xiphophorus hybrid fish model. Proceedings of the National Academy of Sciences,   DOI: 10.1073/pnas.1000324107

Nigrelli, R.F.  1934. Pseudo-melanosis in the tail of trout and salmon.  Copeia 1934(2):61-66.

Patton, E.E., D. L. Mitchell, and R.L. Nairn.  2010.  Genetic and environmental melanoma models in fish.  Pigment Cell Melanoma Research 23:314-337.

Rakers, S., M. Gebert, S. Uppalapati, W. Meyer, P. Maderson, A.F.Sell, C. Kruse, and R. Paus.  2010.  ‘Fish matters’: the relevance of fish skin biology to investigative dermatology.    Experimental Dermatology 19:313-324.

Smith, G.M., and C.W. Coates.  1936.  Cutaneous melanosis in lungfishes (Lepidosirenidae).  Biological Bulletin 71(2):282-285.

Sweet, M., N. Kirkham, M. Bendall, L. Currey, J. Bythell, and M. Heupel.  2012.  Evidence of melanoma in wild marine fish populations.  PLOS One 7(8): e41989. doi:10.1371/journal.pone.0041989

Zodrow, J.M., and R.L. Tanguay.  2003.  2,3,7,8-Tetrachlorodibenzo-p-dioxin inhibits Zebrafish    caudal fin regeneration.    Toxicological Sciences 76(1):151-161.    

On Becoming An Ichthyologist, by Don Orth

Even if you do not see yourself in a career as an Ichthyologist, your learning will be improved by assuming the role and seeking to become an Ichthyologist.   Just accepting the notion that "I am a novice" or "I am becoming" will make it easier for you to ask questions.  My own thinking about becoming an Ichthyologist began a long time ago.

 

I was born and raised on the south side of Chicago, in a neighborhood known as West Englewood.  Fish was what we ate on Fridays, not a potential career aspiration.  At age 10 I got my first paper route, delivering the Chicago American in the Marquette Park and West Englewood neighborhoods.  On weekends, my buddy Michael D. and I would lash our fishing poles to our bikes and ride to Marquette Park, where we fished in the park lagoon (catch and release before it was fashionable).    

In the summers we took the CTA bus to Rainbow Beach to cool off and pretend to swim in Lake Michigan.  In 1967, we were surprised when our beach visits meant we had to endure smells from huge windrows of dead alewives that now dominated the beach.  No one knew why these fish were dying, ruining our beach experience.   I was curious and that curiosity about what is happening underwater has driven me ever since.  Many years later I read a report written by Edward Brown, U.S. Bureau of Commercial Fisheries; he described the massive fish kills that occurred throughout the lake in 1967 and summarized observations without confirming a cause (Brown 1968).  We will discuss this die off phenomenon when we discuss Homeostasis in Fishes.  

 A Live Alewife Alosa pseudoharengus  Photo: Jim Negus

I enjoyed fishing and used my weekly paper-route earnings to buy Outdoor Life.   One day I read an ad that referred to people called Ichthyologists who studied fishes.  This was my Archimedes “Eureka moment.”    “Eureka! I have found it!”   It was an early discovery that there were people who made their living by studying fish.  Imagine that!  I have been becoming ever since.

The notion behind "becoming" is known as the community of practice (CoP) model, developed and studied by cultural anthropologist, Jean Lave, and educator Etienne Wenger (Wenger 2007).   This is a shift from "learning from the teacher" and involves learning through engagement in a community of practice.   As a novice, we are at the periphery of the community of practice and there are rituals, practice, and collaboration that we need to engage with to become bona fide members of the community of practice.   In thinking through the learning activities that I assign, every action is a chance for you to move from a position from the periphery of this CoP to a more involved part of the CoP.   Mastery takes repetitive practice with others.  
 

Graphic depiction of the community of practice model of Jean Lave and Etienne Wenger. Source. 

How can you join the CoP?   Volunteer with other fish-heads and adopt a curious attitude; everyone has something to teach you.    There are more fish-heads on the Virginia Tech campus than there ever were in my West Englewood neighborhood.  Everything we do is easier if we do it in a group.   Catch you own fish.  Learning to outwit an animal with a brain as small as a pea is essential to keep you humble as you become a proud Ichthyologist.   Watch fish.  Keep fish alive in an aquarium.   Make intelligent observations about fish.   Photograph fish.  Post stories about what you are learning on Facebook, Twitter, Flickr, Pinterest, Instagram, or whatever networks you like.  Once you start to share, you will connect with others in the Fish-head CoP.   If you do not contribute to the learning of others, you are not a member of the CoP, you are just another stalker at the periphery of the group.

 

Joining the Fish-head community of practice may resemble joining a religion and you will find that you begin to study religiously!   In Religion for Atheists, Alain de Botton points out that there's a great difference between a sermon and a lecture!  Religions realize that we need ritual, repetition, and an emphasis on the practical value of lessons. You will need to be curious and develop a ritual of observing fish, collecting and practicing the tasks that all Ichthyologists do.  The French naturalist Constantine Rafinesque once wrote  "The art of seeing well, or of noticing and distinguishing with accuracy the objects which we perceive, is a high faculty of the mind, unfolded in a few individuals, and despised by those who can neither acquire it, nor appreciate its results."

You cannot obtain the tacit, know-how, and thinking knowledge of an Ichthyologist from reading a text alone.  Textbooks are filled with the explicit kinds of knowledge.  What you need most of all is to participate in the rituals we practice and do these many times, each time gaining that tacit knowledge held within the community of practice we refer to as Fish-heads. 

 

I am still becoming an Ichthyologist.  When you read a text, do not read it as a student, read it as one who is becoming an Ichthyologist.  When you dissect a new fish specimen, do it not as a student, but as one who is becoming an Ichthyologist.  Every new fish specimen you encounter is a part of your journey toward becoming an Ichthyologist.

References

Brown, E. H., Jr.  1968.  Population characteristics and physical condition of alewives, Alosa pseudoharengus, in a massive dieoff in Lake Michigan, 1967.  Great Lakes Fishery Commission Technical Report 13.

Wenger, Etienne (.ca 2007) ‘Communities of practice. A brief introduction’. Communities of practice [http://wenger-trayner.com/theory/  Accessed February 8, 2014].

Three key dimensions of any community of practice are (1) kind of knowledge, (2) community interaction and identity, and (3) integration of sharing knowledge and work.    Source.

On the value of zooming in, by Don Orth

The semester is over, final grades are submitted, and all but the graduating students have left campus.    At this point, students of Ichthyology may be more frustrated and less fascinated by the enormous diversity of fishes.    In lab we introduced students to over 74 of the 515 families of fishes in the world.     From the monospecific Amiidae (bowfin) to the species-rich Cyprinidae (minnows and carps), each group of fishes presents different challenges for identification.   Some, such as the gars are so unique that you will never misidentify one, whereas others, in particular the sculpins, are easily confused even by the experienced fish specialists.   The week before the final lab practical we visited and sampled two tributaries of the New River drainage.    Over 89 fish taxa are known in the upper New River drainage and 48 are native and 8 are endemic.   When sampling a single reach we are, in fact, zooming in from the zoogeographic pool of likely fishes to the specific assemblage that is present at the site.   Here local factors, such as elevation, channel slope, temperature, and physical habitat will influence the fish species we encounter.   Small high-elevation mountain drainages may have only a few species, such as brook trout, blacknose dace, and mottled sculpin, while the larger downstream reaches may support 12 to 15 species.     In diagnosing fish species, I also preach the value of zooming in.    

Photo of Blacknose Dace Rhinichthys atratulus, Sinking Creek near Newport, Virginia. Photo: D. J. Orth

For weeks the students were learning characteristics and annotated their specimens based on examination of specimens preserved in ethanol.   Often the name was in the jar - no challenge there.  As I watched the students faced with an unknown live and squirming specimen, I encouraged them to “Tell me what you see. What do you think it is?”   Students have been learning to start with the bigger categories and drill down to likely species by zooming in on diagnostic characteristics.     For example, the minnows can be bewildering until the student learns to zoom in on characteristics of the mouth, or scale size and pattern.   Most minnows have a small terminal mouth, so any variation from this is important.   A ventral mouth may mean a Rhinichthys dace, Kanawha minnow, cutlips minnow or central stoneroller.   Zooming in on the characteristics of the mouth will quickly reveal the diagnostic character of the species.     For example, the cutlips and tonguetied minnows are distinguished for all other minnows by its three-lobed lower jaw with middle lobe sticking out like a tongue (photo on left).  This adaptation allows it to capture miniscule gastrods and insect larvae, which it scrapes from rocks, and also assists the male cutlips minnow who builds a nest of small pebbles; click here to view a video.     The lower jaw of the Central Stoneroller has a hard cartilaginous ridge (photo on right) which it uses to scrape ooze from the stream bottom.  It gets its name by the habit of the male excavating a nest by moving gravel with its nose. 

Close-up photos of the ventral view of the mouth of  Cutlips Minnow Exoglossum maxillingua  (Photo by Dylan Hann) and Central Stoneroller Campostoma anomalum   (Photo by D. J. Orth.)

It is spring time and the males of many species are showing the special secondary sexual characteristics.   The Nocomis chubs and Campostoma stonerollers already have tubercles on the heads, and white suckers and hog suckers have tubercles on anal and caudal fins.     The male fantail darter Etheostoma flabellare  develops little egg mimics at the tips of his spiny dorsal fin.  The fantail darter selects a large flat cobblestone in riffles for a nest site and the female lays eggs on underside of the cobble while the male fertilizes and guards the developing embryos.      The egg mimics are a bit of visual trickery as the females searching for a suitable mate and nest site see there are already eggs in the nest.   In fact, in an elegant experiment, Knapp and Sargent (1989) demonstrated that females preferred males with eggs over males without eggs, and furthermore that females preferred males with egg-mimics over males without egg-mimics.    Therefore, female choice played a major role in the evolution of the egg-mimics in fantail darters.

Fantail darter Etheostoma flabellare  from Sinking Creek near Newport, Virginia.  Note the egg mimics at tips of spines of first dorsal fin in this male specimen.   Photo by D. J. Orth

The week after our field trips, a spring storm dumped heavy rains and these easily-waded streams now overflowed their banks.   The large flat cobblestones selected as nest sites by the fantail darter are highly resistant to being entrained and mobilized in these common spring floods. The cavity under the cobblestone is also inaccessible to potential egg predators.   I am certain the less-selective male fantail darters soon learn the hard way the value of finding a nest site below a big, stable cobblestone.  

The sculpins (Cottidae) are a group of bottom-dwelling fishes that are widely distributed in temperate regions of North America and Eurasia.  They exhibit extreme variation in morphology and species are difficult to characterize and identify.  While the group is not as species-rich as either the darters or minnows,  their identification may stymie the novice Ichthyologist until s/he learns to zoom in on the characteristics.   Streams we sampled had both the Mottled Sculpin Cottus bairdi and the Kanawha Sculpin Cottus kanawhae (formerly considered a subspecies of banded sculpin Cottus carolinae carolinae Robins 2005).       Here I include close-up photos to show the pigmentation patterns of the dorsal fins and chins. 

Dorsal fins of the Kanawha Sculpin (top) and the Mottled Sculpin (bottom).  Photo by D. J. Orth

Sculpins are so well camouflaged to match the stream bottoms that anglers are seldom aware that the streams they fish are loaded with sculpins.   Some fly tiers have learned to mimic the color and pattern of the sculpin with streamer patterns.  In fact the world-wide favorite Muddler Minnow was created to mimic a sculpin.    These are effective for a variety of game fishes as long as they are fished right on the bottom and fished slowly, with occasional twitches to mimic escape action.    

Chins of the Mottled Sculpin (left) and the Kanawha Sculpin (right).  Photos by D. J. Orth

The family Cyprinidae (minnows and carps) is one of the largest families of fish in the world (over 2,400 species in the last authoritative count) and these are often the most abundant fishes in freshwater streams.   The diversity of the Cyprinidae is truly impressive on a global scale and when we zoom in on the Virginia waters we have 67 species.    All the minnows have one dorsal fin, pelvic fin in abdominal position,  pectoral fin low on the body, and lack an adipose fin.   Beyond that one needs to zoom in the lower jaw, tiny barbels, pigment patterns, scale size and pattern, and even fin ray counts.  The first fish we captured in Toms Creek was a very small minnow, a rosefin shiner Lythrurus ardens.   I didn't think the students would be able to identify it, but when they zoomed in to observe the diagnostic characteristics, they nailed it.

Telescope Shiner  Notropis telescopus from Sinking Creek near Newport.  Photo by D. J. Orth

White Shiner Luxilus albeolus from Sinking Creek near Newport.   Photo by Jessica Dodds.

Close up photos of the dorsal scales of the Telescope Shiner (top) and lateral line scales of the White Shiner (bottom).  Photos by D. J. Orth.

Telescope shiner and white shiner are depicted in these photos    --   when I first learned Ichthyology these two were in the same genus Notropis, a lot of things were easier back then.   But when we zoom in, to the scale patterns we see important differences.   Telescope shiner had dark scale margins in the nape and dorsolateral scales and the scales are larger and irregularly shaped, leaving a distinct zig-zag line pattern.   The White Shiner is in the genus of high-scale shiners (Luxilus) so named for the exposed scales in lateral line that are twice as high as the exposed width -- something you only notice when you zoom in.  

We encountered two species of Rhinichthys, the daces.  The genus name Rhinichthys translates to "snout fish" in reference to the prominent snout.   Here zooming in requires the observer to be more precise about the pattern or proportions.    The blacknose dace has a blacknose, the longnose dace has a longnose, yet the correct identification requires us to be more precise about “how long is the long nose?”   We must zoom in to interpret.     The two species co-occur in Ridge-and-Valley and Blue Ridge streams and are often easy to confuse. 

Photos of head (lateral view) and ventral view of mouth of Longnose Dace Rhinichthys atratrulus.  Photos by D. J. Orth.

There is much value in zooming in and ever since my close-up vision was compromised by middle-age, I have had to rely on a magnifying lens to assist me when zooming in.      There is plenty to do while sampling for fish in our local streams or sorting through a net full of fish.   Zooming seems like one of the last things to do after obtaining a sample, but it is an essential part of the fascinating study of the fishes.    To my Proud Ichthyology Students of 2013, go forth and catch many fishes, use your newfound knowledge to earn an honest living, share  your enthusiasm for fish and their habitats with family and friends, never be satisfied with the status quo, and know when you need to zoom in.

References

Knapp, R. A.,  and R. C. Sargent.   1989.  Egg-mimicry as a mating strategy in the fantail darter, Etheostoma flabellare: females prefer males with eggs.  Behavioral Ecology and Sociobiology 25:321-326.

Robins, C. R.  2005.  Cottus kanawhae, a new cottid fish from the New River systems of Virginia and West Virginia.   Zootaxa 987:1-6.

We have a winner -- Fishing Lure Design

This extra credit assignment was designed to integrate your knowledge of fish anatomy, sensory systems, feeding, and water conditions to create an effect lure design. All students were provided the same size wooden lure blank. This extra credit assignment was designed to encourage students to apply both knowledge of fish and creativity to design a lure to catch fish. 

Students  submitted a completed lure (without hooks and hardware) with a 200-word description and the design was evaluated based on (1)  marketing appeal,  (2)  mimicry, (3) rationale for design and lure name, and (4) artistry.   

The entries included such notable names as the American Shad Popper, Tubular Tubercle Chub, The Weakest Link, Royal Gramma Grabber, Northern Fire-glacier Minnow, and the Heart Snatcher.     The top scoring entry was the Alosa, a 6 inch, 1.5 ounce topwater bait, handcarved to mimic the Alosa forage fish.  

The Alosa.  Note the individually defined scales, countershading color pattern, and pearlescent paint finish.  This lure is sealed with several coats of lacquer  and ready to to be outfitted with treble hooks and fished immediately.  Britney Kreiner

Other contenders for top lure design include the following:

Tubular Tubercle Chub with life-like scales and eye popping refracting color to trick any predator.  Caitlin Worsham

The Heart Snatcher is designed with vibrant colors and silvery sheen to mimic the Rosyside Dace.  Jeanne Change

Musky Pop-R is designed to be a top-water plut and spits and throws water.  Its flared gill operculum provides a convincing silhouette.   Zach Moran.

This pencil -popper style lure simulates a fish fleeing at the water's surface. The body coloration mimics the American Shad with blueish yellow top coat and silvery white underside.   Ashley Weston

Congratulations to the winner and all entrants who spent time thinking about how to catch fish.