Wednesday, December 21, 2016

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
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

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