Sea Lamprey and Unexpected Costs of Shipping, by Don Orth

Among the many invasive fishes, one of the best-studied invasive fish is the parasitic Sea Lamprey (Petromyzon marinus).  Sea Lamprey is the subject of many vertebrate anatomy labs because they represent a morphologically simple fish.  The Sea Lamprey skeleton is cartilaginous, and they lack jaws, scales, and paired fins.  Sea Lamprey have two closely spaced dorsal fins, functional eyes, and seven gill openings.  The mouth of this blood-sucking parasite is most unique.  Sea Lamprey have a circular oral disc with circular rows of sharp, curved teeth and file-like tongue.  After latching on to a large-bodied fish, the Sea Lamprey uses its teeth to rasp through the skin and feed on the blood. The host may die directly from loss of fluids or indirectly from infections of the wound.  If the host fish survives, it may be attacked again by another feeding Sea Lamprey. The Sea Lamprey is an anadromous species native to the North Atlantic Ocean; they breed in rivers in Europe and North America from Newfoundland to Florida.  Sea Lamprey are in the order, Petromyzontiformes, which encompasses forty known species of lampreys worldwide. However, landlocked populations in the Great Lakes have gotten most attention by scientists and anglers, who have crafted the narrative of invader to control at all costs.

Sea lamprey adult. Photo by Oskar Sindri Gislason

Sea Lamprey were a major, or final, cause of the collapse of major commercial fisheries for Lake Trout Salvelinus namaycush, several Whitefishes Coregonus spp., Burbot Lota lota, and Walleye Sander vitreus in the 1940s and 1950s.  Because the Sea Lamprey reduced populations of these large piscivorous fishes, the next invasive fish to arrive, the Alewife Alosa pseudoharengus, quickly become the dominant prey fish in Lakes Ontario, Huron, and Michigan.  The expansion of the Alewife led to introduction of trout and salmonine fishes in 1968 and creation of new multi-million dollar recreational fisheries.  That management controversy is a subject for another essay (Kitchell and Sass 2008; O’Gorman et al. 2013). 

Sea Lamprey oral disc. Photo by Cory Genovese

Expensive and persistent control efforts to reduce abundance of Sea Lamprey began in Lake Superior and spread eastward so that lamprey control in Lake Ontario began in 1971 and suppression was not evident until 1988.  Current control relies primarily on stream application of two lampricides, 3-trifluoromethyl-4-nitrophenol (don't you love organic chemistry now?), or more simply TFM, and Bayluscide.  TFM and Bayluscide are applied to kill larval Sea Lampreys before they metamorphose and emigrate from spawning streams.  Other control techniques include harvest of adults via trapping, and low-head barriers built to reduce the amount of stream habitats that need to be treated with TFM. For more background, view this video Silent Invaders.   Along with effective Sea Lamprey control efforts, harvest controls, stocking, and restoration have also increased abundance of large-bodied fishes, which are hosts for Sea Lamprey. If they did not have such large economic effects, basic questions on the species would not have been addressed.  Consequently, we know a lot about the Sea Lamprey, certainly more than any other lamprey in the world.

The conventional wisdom always held that the Sea Lampreys first entered the Great Lakes in the 1800s through the man-made locks and shipping canals around Niagara Falls.  Niagara Falls was a natural barrier to Sea Lamprey migration above Lake Ontario.  Completion of Erie Canal provided access to from the Hudson River to Lake Erie. Modification of Welland Canal in 1919 provided access between Lake Ontario and Lake Erie. Consequently, Sea Lamprey first appeared in Lake Erie in 1921, and subsequently were documented in Lake Michigan (1936), Lake Huron (1937), and Lake Superior (1946). But what about the status of Sea Lampreys in Lake Ontario?  Recent DNA analyses supports hypothesis that Sea Lamprey are indigenous to Lake Ontario and introduced in other Great Lakes (Waldman et al. 2004, 2006). Unique alleles found in Lake Ontario, but absent in the Atlantic coast collections, would have taken many thousands of years to develop (Waldman et al. 2009).  It is likely that the populations of Sea Lamprey in Lake Ontario and its tributaries, the Finger Lakes, and Lake Champlain once represented relict populations from the last Pleistocene glaciation.  

Erie Canal (Top) source  and Welland Canal (bottom) source

Because of the emergence of the Sea Lamprey and their economic impacts in the upper Great Lakes, much has been learned about the Sea Lamprey.   How they locate their spawning grounds?  How do they locate mates?   The key is chemical, or pheromone-based communication.    Larvae, or ammocetes, and adult males produce and release unique bile acids.  Adults have a small nasal opening at the top of the head and can detect these bile acids at picomolar concentrations (Li et al. 1995; Li et al. 2002).   These finding led to the hypothesis that the bile acid compounds serve as pheromones.   Controlled behavioral tests supported the hypothesis that the pheromones released by larvae and transported downstream and serve to direct the migration of adults females (Bjerselius et al. 2000; Sorensen and Vreize 2003; Sorensen and Stacy 2004).  This research supports the evolutionary role that pheromones have played as chemical cues to the suitability of spawning and rearing habitat for the Sea Lamprey. This research also paved the way to consider another approach to Sea Lamprey control.  Migratory Sea Lamprey rely heavily on olfactory cues to locate river mouths and direct their upstream movement within rivers (Vrieze et al. 2010).   Pheromones could be used to divert migratory Sea Lamprey to tributaries where they may be trapped, poisoned, or sterilized.  Note the large olfactory bulbs in the lamprey brain image below.  

Sea lamprey brain after R.H. Burne

 Many anadromous fishes use olfactory cues to return to their natal home for spawning. Fish, such as Atlantic Sturgeon, Atlantic Salmon and Striped Bass, show significant differences in haplotype frequencies among rivers.  However, the Sea Lamprey do not return to their natal streams for spawning.  As parasites, the tendency for a regular migration circuit and return to a home river is problematic as their host fishes may disperse the parasite widely.   When adults reach maturity they quit feeding and need to find a suitable river for breeding.    Waldman et al. (2008) collected fin clips from Sea Lamprey from eleven Atlantic Slope rivers.  Examination of haplotype frequencies from mitochondrial DNA confirmed a very low variation among river collection sites. Therefore, the Sea Lamprey regularly inter-breed among rivers and demonstrate a regional panmixia and not homing (Waldman et al. 2008).    

With this knowledge, can we control the invasive Sea Lamprey more effectively?  In theory, yes.   Trapping alone in the absence of lampricides is not sufficient to control Sea Lamprey populations (Holbrook et al. 2016).  However, research is underway now to evaluate strategies to integrate multiple control strategies.   One technique releases large numbers of sterile males in an attempt to thwart successful reproduction.  These sterile males still produce sperm, but that sperm is genetically damaged, thereby reducing the number of viable embryos via lethal mutations.  Sterile release strategies, first tested in the early 1990s in the St Mary’s River, reduced survival of embryos in nests by half (Bravener and Twohey 2016). The graph below supports the significant effect that proportion of sterile males observed on nests had on the mean embryo viability of all nests.

 

Plot of embryo viability and proportion of sterile males on nests (Bravener and Twohey 2016).

The solid line represents the theoretical relationship under a baseline embryo viability of 43.4%. The dashed line represents the line of best fit to the 14 data points.

Another technique uses pheromones to disrupt migrations or attract spawners to areas where sterile males are released and/or where spawning adults may be more effectively trapped.  The pheromone compound can now be synthesized, which makes the technique operational.  The pheromone compound is 7α, 12α, 24-trihydroxy-3-one-5α-cholan-24-sulfate (don’t you love organic chemistry?), or more simply 3k PZS (Li et al. 2012).  Costs to synthesize 3k PZS have decreased substantially in the last ten years (Johnson et al. 2013). Dawson et al. (2016) evaluated strategies for pheromone-baited trapping by calculated expected control and their costs.   The findings support combining lampricides and pheromone-baited trapping technologies at comparable costs.  

 Sea Lamprey wound on Steelhead.    Photo by Boris Kitevski source

While the basic research on the Sea Lamprey has great potential to make control efforts more cost effective, costs will continue into the future.  The current management strategy for some Great Lakes fisheries depends on a strategy of stocking piscivores to drive down populations of the invasive Alewife and Rainbow Smelt and thereby reduce competition and predation effects of these invaders.  This strategy works, however, the net effect is more large-bodied fishes that serve as hosts for the parasitic Sea Lamprey.   Stocking piscivores provides more food for Sea Lamprey and leads to competition among salmon, lake trout, and burbot.  In addition, other invasives, including Zebra Mussel, Quagga mussels, Round Goby, and Tubenose Goby will most certainly complicate the future of Great Lakes fisheries.    There is no simple solution to living with invasive fishes.   In closing, remember that where you stand regarding the Sea Lamprey depends on where you sit.  The Sea Lamprey in its native range do not drive down abundance of large bodied fishes. Rather than a scourge, they play important roles.  In tributaries they are ecosystem engineers, creating patches of deep, rocky, and swift water next to deep, slow, and sandy habitat patches, as well as higher density of benthic invertebrates (Hogg et al. 2014).  

References

Bjerselius, R., and eight coauthors. 2000.  Direct behavioral evidence that unique bile acids released by larval sea lamprey (Petromyzon marinus) function as a migratory pheromone.  Canadian Journal of Fisheries and Aquatic Sciences 57:557-569.

Bravener, G., and M. Twohey. 2016. Evaluation of a sterile-male release technique: A case study of invasive Sea Lamprey control in a tributary of the Laurentian Great Lakes. North American Journal of Fisheries Management 36:1125-1138.

Dawson, H.A., M.L. Jones, B.J. Irwin, N.S. Johnson, M.C. Wagner, and M.D. Szymanski. 2016. Management strategy evaluation of pheromone-baited trapping techniques to improve management of invasive sea lamprey.  Natural Resource Modeling 29:448-469.

Hogg, R.S., S.M. Coghlan, Jr., J. Zydlewski, and K.S. Simon.  2014.  Anadromous sea lampreys (Petromyzon marinus) are ecosystem engineers in a spawning tributary.  Freshwater Biology 59:1294-1307.

Holbrook, C.M., R.A. Bergstedt, J. Barber, G.A. Bravener, M.L. Jones, and C.C. Krueger.  2016.  Evaluating harvest-based control of invasive fish with telemetry: performance of sea lamprey traps in the Great Lakes.  Ecological Applications 26:1595-1609.

Johnson, N.S. M.J. Siefkes, C.M. Wagner, H.A. Dawson, H. Wang, T.B. Steeves, M. Twohey, and W. Li. 2013. A synthesized mating pheromone component increases adult sea lamprey (Petromyzon marinus) trap capture in management scenarios.  Canadian Journal of Fisheries and Aquatic Sciences 70:1101-1108.    

Kitchell, J. F., and G. G. Sass. 2008. Great Lakes ecosystems: Invasions, food web dynamics and the challenge of ecological restoration. Pages 157–170 in D. Waller and T. Rooney, editors. Ecological history of Wisconsin. University of Chicago Press, Chicago, Illinois, USA.

Li., W., P.W. Sorensen, and D.G. Gallaher. 1995. The olfactory system of the migratory sea lamprey (Petromyzon marinus) is specifically and acutely sensitive to unique bile acids released by conspecific larvae. Journal of General Physiology 105:569-587.

Li, W., A.P. Scott., M.J. Siefkes, H. Yan, Q. Liu., S.-S. Yun, and D.A. Gage. 2002.  Bile acid secreted by male sea lamprey that acts as a sex pheromone.  Science 296:138-141. 

Li, K., M.J. Siefkes, C.O.Brant, and W. Li. 2012. Isolation and identification of petromyzestrosterol, a polyhydroxysteroid from sexually mature male sea lamprey (Petromyzon marinus L.). Steroids 77:806-810.

O’Gorman, R., C.P. Madenjian, E.F. Roseman, A.Cook, and O.T. Gorman. 2013. Alewife in the Great Lakes: Old invader – New millennium    Pages 705-732 in W.W. Taylor, A. J. Lynch, and N. J. Leonard editors. Great Lakes Policy and Management: A Binational Perspective, 2nd edition. Michigan State University Press, East Lansing

Sorensen, P.W., and L.A. Vrieze. 2003. The chemical ecology and potential application of the Sea Lamprey migratory pheromone. Journal of Great Lakes Research 29(Supp 1):66-84.

Sorensen, P.W., and N.E. Stacey. 2004.  Brief review of fish pheromones and discussion of their possible uses in the control of non-indigenous teleost fishes.  New Zealand Journal of Marine and Freshwater Research 38:399-417.

Vrieze, L.A., R. Bjerselius, and P.W. Sorensen. 2010.  Importance of the olfactory sense to migratory sea lampreys Petromyzon marinus seeking riverine spawning habitat. Journal of Fish Biology 76:949-964.     

Waldman, J.R., C. Grunwald, N.K. Roy, and I.I. Wirgin. 2004. Mitochondrial DNA analysis indicates sea lampreys are indigenous to Lake Ontario. Transactions of the American Fisheries Society 133:950-960. 

Waldman, J.R., C. Grunwald, and I.I. Wirgin. 2006. Evaluation of the native status of sea lamprey Petromyzon marinus in Lake Champlain based on mitochondrial DNA sequencing analysis. Transactions of the American Fisheries Society 135:1076-1085.

Waldman, J., R. Daniels, M. Hickerson, and I. Wirgin. 2009. Mitochondrial DNA analysis indicates sea lampreys are indigenous to Lake Ontario: response to comment. Transactions of the American Fisheries Society 138: 1190-1197.

Fluvial Fishes Lab 2016

What mattered in 2016? Did we get published? Did it get read? Did it get cited? Did it make any difference? Can we make the next paper even better?   The research cycle continues as we celebrate the end of 2016.  

It never fails.  Whenever a submitted, revised, and revised and revised manuscript is finally acceptable for publication in a journal, I feel vindicated.  Sometimes I will spontaneously begin singing Queen's "We are the champions.  The process of research certainly feels like a "Hero's journey" to the authors.  There are no easy publications.  Each is a long struggle that ends in organizing a manuscript into the standard IMRAD template. This template has been used forever, but it  devalues the real process and excitement of discovery.   

In 2016, the Fluvial Fishes Lab completed papers and projects and we worked more on delivering and tailoring the message to other members of the public, hoping to make the science matter. All lab members are enthusiastic about explaining their work to members of the public.  Two noteworthy books I read this past year were Randy Olson's Houston, We Have a Narrative (Univ. Chicago Press, 2015) and Nancy Baron’s Escape from the Ivory Tower: A Guide to Making Your Science Matter  (Island Press, 2010).  Each provides many practical suggestions for making connections with the public.

In 2016,  Gary Grossman,   Jason Neuswanger, and I published  “Innovative Approaches to Fisheries Education and Outreach in Fisheries.” It was an interesting collaboration, as we reflected on changes in college teaching over the past decades.   In 1995, I published an article in Fisheries entitled “Pogo Was Right, Let’s Change the Way We Teach Fisheries.”  Twenty years later we wrote,  "Despite the prescience of Orth’s (1995) article, many of the same problems remain in Fisheries education today."  This has to be the first time my name and “prescience” has been used in the same sentence.    If interested, you can read about the use of the use of music, ukulele, karaoke, ePortfolio, troutnut, and other contemporary approaches in education.  We remain hopeful that further pedagogical innovation will result in fisheries having a “signature pedagogy.”

In a paper on species distribution models (SDMs) of New River fishes, Jian Huang, Emmanual Frimpong and I examined the temporal transferability of these SDMs in terms of discrimination power and calibration with the temporarily independent datasets.   We used lasso-regularized logistic regression (LLR), boosted regression trees (BRT), MaxEnt, and ensemble models (ENS) to evaluate the habitat suitability of 16 fish species.  Climate change is the most influential disturbance on fishes and these types of models will be more commonly employed to project future changes in species distributions.  However, biases, under-fitting, and overfitting were common issues to address in temporal transferability.  

Our analysis of catfish feeding before, during, and after the spring migration of Alosine fishes is in press in Marine and Coastal Fisheries.  The study depended on methods for identifying partially digested unidentifiable fish (PDUF) with DNA barcodes.    The paper was the first to examine which species of Alosa occurred in guts of Flathead Catfish and Flathead Catfish. In this time frame, the Blue Catfish had broad, omnivorous diets, while Flathead Catfish fed solely on other fish. However, there were important spatial and temporal differences in diets.  Alosa species were consumed at higher frequency in the non-tidal, freshwater areas  than in oligohaline and mesohaline sites. Flathead Catfish are likely to have a greater per-fish impact on depleted Alosa species than the Blue Catfish. Further, dams and complex river structures appear to increase the vulnerability of alosines to predation by large catfishes.  We are now completely done with sampling catfish stomachs and busy with the analysis of data.    

Blue Catfish Ictalurus furcatus source

An opportunistic encounter with Clinch Dace during a spawning event eventually was accepted as a Note on spawning behavior  by Hunter Hatcher et al. (in press, The American Midland Naturalist) after many hours watching videos and interpreting behaviors, waiting for a brief release of gametes. 

Rock Bass recruitment in the New River has never been examined previously.  Pearce Cooper examined historic data sets and aged Rock Bass in the New River to examine major drivers of recruitment variation.   At two locations downstream from Claytor Lake Dam, high streamflow events after spawning reduced recruitment of Rock Bass at age-1.  The paper is available here. 

The relationship between average and maximum discharge (cm/s) in the previous year and the catch per unit effort (CPUE, # fish/h) of age-1 Rock Bass at the upstream and downstream sites during the months the relationship was found to be significant.

Michael Moore defended his Masters Thesis on the yeller finned minners in spring and began a PhD program at University of Missouri.  He'll move up from studying small, fragmented populations of a small minnow to studying small, fragmented populations of large sturgeon.  The final report to the Department of Game and Inland Fisheries,  “Distribution and Population Characterizationof Clinch Dace (Chrosomus sp. cf. saylori) in the Upper Clinch River System, Virginia” provides a plan for conserving remaining populations.
 
Objectives of this project were to (1) examine the historical changes in these watersheds to quantify features of historical Clinch dace streams; (2) confirm presence and relatedness of within-stream subpopulations separated by putative barriers; (3) identify and verify presence/absence of Clinch dace in the 125 km not previously sampled; (4) survey for spread in distribution of other Chrosomus in putative range of Clinch dace; (5) develop outreach plan landowners to protect extant populations. Clinch Dace occur at low densities in approximately 31.5 km of headwater streams. The mean estimate of global population size was 6,706 individuals. Most populations are likely influenced by low genetic diversity. Therefore, we examined 15 candidate conservation areas; ten of these areas have abandoned mine sites with $12.5M in unfunded restoration costs. The best candidate areas for conservation of Clinch Dace are: Pine Creek, Big Lick Creek, Mudlick Creek, and Hurricane Fork.

This is me after Bells Palsy paralyzed my facial nerves. Muscles on the right side of my face would not move.

In June I experienced sudden paralysis of the facial muscles on my right side. Paralysis of the facial nerve was caused by virus and inflammation and treated with antiviral and anti inflammatory medications.  The original prognosis that voluntary movement would gradually return in 3 to 6 months proved correct.  The facial nerve, or cranial nerve VII, is the nerve of facial expression. It is composed of approximately 10,000 neurons, 7,000 of which are myelinated and innervate the nerves of facial expression. That explains the slow regeneration time.

In September, I created and delivered my first Pecha Kucha presentation for Blacksburg Sustainability Week.  This concise format requires 20 slides of 20 seconds each, and makes it impossible to be spontaneous.   View it here.

Two new studies were funded in 2016.  One is a biological survey of the New River in the vicinity of the Fries Hydroelectic project; this is a collaboration with Verl Emrick and Caitlyn Carey, of the Conservation Management Institute. 

Google Earth photo of New River above Fries Dam. Note the mid-channel island built from the trapped river sediments.

The other new study, with Eric Hallerman, will examine genetic divergence in small populations of the Clinch Dace. This study will be led by Rebecca Bourquin, who left a position at Maryland Biological Stream Survey to begin her graduate studies last fall. 
 
The Virginia Tech Ichthyology blog had 54 posts for 2016.   The most viewed blogpost of the year was "Dammed If You Do:  Adopting Social Media in Teaching."   At the American Fisheries Society Annual Meeting in Kansas City, I was awarded the Excellence in Fisheries Education Award and named American Fisheries Society Fellow. 
 

Awarded the Excellence in Fisheries Education Award.  With Ron Essig and Jesse Trushenksi at the American Fisheries Society Meeting

Hunter Hatcher graduated in spring and sampled the New River near Fries Dam before beginning his Masters studies at Mississippi State University. 

Hunter Hatcher gets photographed at the Mudbass Classic 2016.

Hae Kim broke his own archery record with a record carp that was 45 lbs. and 7 oz.  It was taken in  Claytor Lake.

Hae Kim with his record carp.   Source.

Research on the non-native catfish is chronicled regularly in a blog, managed by PhD student, Joseph Schmitt.  You can read about our work at http://www.chesapeakecatfish.com/.
 

Recognition at 2016 Service Dinner

 
 

Payara - What Big Teeth You've Got, by Don Orth

Many fish have teeth -- that is no surprise.  But one fish reminds me of the exchange between Little Red Riding Hood and the Big Bad Wolf.  Red Riding Hood says "Oh Granny, what big teeth you've got!" and the wolf replies "All the better to eat you with, my dear!"

The Payara, a fish from the Amazon, has amazing long and sharp fangs on the lower jaw.  These are also called vampire tetras or dogtooth characins and the fangs make them specialized predators.   The scientific name for one species is Hydrolycus scomberoides.  ‘Hydrolycus’ is from the Greek 'hydro,' meaning ‘water’, and ‘lykos,’ meaning ‘wolf’. The species names ‘scomberoides’ is from the Greek skombros, meaning ‘tuna, mackerel’, and the suffix -oides, meaning ‘similar to.’   You can watch this video of this strange vampire fish in captivity and imagine what it might be like to encounter one in the wild. 

Upper jaw (ventral view) of the Payara (Toledo-Piza 2000)

These long fangs actually fit neatly into pockets in the skull; otherwise the fish could not close its mouth. Do people fish for them?  Yes.  Can you eat them?  Yes.  Can I keep them in your aquarium?  Yes, uh, well only the small ones.  There are several species and much more to learn about them.  Some species support subsistence fisheries, but the Payara has garnered international reputation among sport fishers.

Hydrolycus scomberoides (lower image) and Rhaphiodon vulpinus (upper image) Source

Consider the fishing possibilities.  Payaras can reach a length of 1.2 m (3.8 ft) and a weight of 18 kg (39 lb).   Watch  this video.    Imagine reeling it in, getting it close, and watching this head shake right before your eyes.

Head on view of the Payara.  Source

The Payara seem to be developing a strong following of adventurous anglers, including Zeb Hogan, Professor and National Geographic Explorer of Monster Fish fame.  He searched for them in Guyana.  "We found the Payara just below the Corona Falls on the Rewa River in Guyana," he said. "It's on the small side for megafish, at 40 pounds and 4 feet long.”    But the Payara has a monster gape and monster fangs to rival any other fish in the world. 

Large Payara Hydrolycus scomberoides caught by a recreational angler in the Orinoco River. Source

The Payara is a member of the family Cynodontidae (Order: Characiformes).  These dogtooth characins are very distinctive neotropical characiform fishes easily recognizable by the oblique mouth, well developed dentary canines, and relatively large expanded pectoral fins. The streamlined, muscular body is covered with small silver scales. They occur in parts of the Amazon and Orinoco basins and rivers that drain Atlantic slopes of the Guianas.  These fish have a long history with fossil specimens from Miocene deposits from western Columbia and Argentina. Three genera (Cynodon 3 species; Hydrolycus, 4 species; and Rhaphiodon, 1 species) comprise the family.  

Ichthyological explorations in the Amazon and Orinoco have observed these fishes in rivers, lakes and flooded forests.  They are mostly mid-water and surface-water dweller – specialized piscivores that use dentary canines to stab prey. The other characteristics, the large eye, laterally compressed body, and large oblique mouth suggests that they are visual hunters that can quickly move to capture live prey fish.    One study of dogtooth characins discovered that the numbers and biomass increased with water transparency, supporting the visual feeding specialization hypothesis. 

Hydrolyclus scomberoides was recently added to International Game Fish Association fly and rod classes.  Watch this video on fly fishing for the Payara in the Bolivian jungle.   Oliver White (2015) has promoted fly fishing for the Payara and claims that the little known area around Uraima Falls, Paragua River, is the best place in the world for large Payara.  This isn’t an easy fishing excursion, even for an experienced fly angler.  It is physically difficult to cast 12-weight with large flies and heavy lines, all the while perched on a rock amidst monster rapids.  

Illustration of the Payara by Duane Raver

Because of its trophic position, the Payara had some of the highest concentrations of methyl mercury among the fishes sampled in Bacajá River, Brazil (Souza-Araujo et al. (2016).  River conditions, lightly acidic pH, high temperature, and high concentrations of nutrients and dissolved minerals, all contribute to bacterial methylation in these waters.  Follow-up studies are needed in order to provide guidelines for fish intake and monitoring and managerial actions.

Other species include the Hydrolycus armatus Sabertooth Characin  and Hydrolycus tatauaia, ‘Cachorra’ or ‘Pirandirá  and Hydrolycus wallacei.    Some captive specimens have been observed in aquaria (see video). Rhaphiodon vulpinus, the Briara, is the only member of this genus.  Rhaphiodon is derived from the Greek rhaphis, meaning ‘needle’, and odous, meaning ‘tooth’.and vulpinus is from the Latin vulpinus, meaning ‘fox’.  The genus, Cynodon, includes other vampire fish (Cynodon gibbus, C. meionactis, and C. septenarius).    

Head detail of specimen of Raphiodon vulpinus, the Briara,  collected from the Paraná River, Argentina. © Claúdio Dias Timm

The Payara and its close relatives are among the thousands of little-studied fishes in South America. It is clear from work done to date that they are important predators, food fishes, and play an important role in these freshwater ecosystems.  However, there are 48 dams greater than 2 MW capacity in the Andean Amazon, and plans for an additional 151 such dams over the next 20 years (Finer and Jenkins 2012).  Given demand for harvest and modification of the river systems for hydroelectric power and development of watersheds for agriculture, these fishes deserve further attention and management. 

Zeb Hogan with specimen of the Payara

References

Finer, M. and C.N. Jenkins. 2012.  Proliferation of hydroelectric dams in the Andean Amazon and implications for Andes-Amazon connectivity. PLoS ONE, 7, e35126.

Melo, C.E., J.D. Lima, and E.F. Silva. 2009.  Relationships between water transparency and abundance of Cynodontidae species in the Bananal floodplain, Mato Grosso, Brazil.  Neotropical Ichthyology 7:215-256.

Reis, R.E., S. O. Kullander, and C.J. Ferraris.  2003.  Check list of the freshwater fishes of south and central America.  Pontifícia Universidade Católica do Rio Grande do Sul. Museu de Ciências e Tecnologia.

Souza-Araujo, J., T. Giarrizzo, M.O. Lima, and M.B.G. Souza.  2016.  Mercury and methyl mercury in fishes from the Bacajá River (Brazilian Amazon): evidence for bioaccumulation and biomagnification.  Journal of Fish Biology 89:249-263. doi:10.1111/jfb.13027

Toledo-Piza, M. 2000. The Neotropical Fish Subfamily Cynodontinae (Teleostei: Ostariophysi: Characiformes): A Phylogenetic Study and a Revision of Cynodon and Rhaphiodon. American Museum Novitates 3286: 1-88

Toledo-Piza, M., N. A. Menezes and G. M. dos Santos. 1999. Revision of the neotropical fish genus Hydrolycus (Ostariophysi: Cynodontinae) with the description of two new species. Ichthyological Exploration of Freshwaters 10(3): 255-280.

White, O.  2015.  Fangs on the fly: Hunting vampires in the Venezuala jungle.   Fly Fisherman Oct-Dec.  10-13.

Zacarkim, C.E., P.A. Piana, G. Baumgartner, and J.M. R. Aranha. 2015. The panorama of artisanal fisheries of the Araguaia River, Brazil. Fisheries Science 81(3): 409–416. DOI 10.1007/s12562-015-0853-z