ATTACKS ON HUMANS

Attacks on humans by the piranha Serrasalmus rhombeus in Suriname

Jan H. Mol 

Center for Agricultural Research in Suriname (CELOS) and Department of Biology, University of Suriname, Suriname

ABSTRACT

Piranhas have a reputation of being man-eating fishes, notwithstanding the absence of well-documented records of piranha attacks on human beings. Three sites in Suriname where piranha attacks on bathers have taken place are discussed. In two isolated villages on the Wayombo River, most victims were children. In one village, 30 piranha attacks occurred in a period of 12 years, bites were mostly on the feet, and injuries were relatively harmless. In the second village, attacks occurred in a period of 7 years, and injuries were more serious, including the loss of digits and large and deep wounds in legs, arms and trunk. Two victims were attacked by several piranhas simultaneously. At the third site, a recreation park on the Suriname River, most attacks involved a single bite on the feet and victims were able to walk back to the beach without being attacked by other piranhas. Piranha attacks on humans did not result in deaths. The recovery of a toe phalange (Wayombo River) and a piece of flesh including a nail (Suriname River) from the stomach of two piranhas identified the fish responsible for the attacks as Serrasalmus rhombeus. Attacks on humans by S. rhombeus were associated with high age 0+ piranha densities in the dry season, high human prey densities, commotion in the water by humans, and spillage of food, fish offal or blood in the water.

From Frank Magallanes

While the above ABSTRACT suggests that these "attacks" are deliberate, one has to read beyond the printed word and see that oftentimes, such attacks occur because of human interference in the natural cycle of life. In other words, these attacks could be the result of construction of dams to eliminate water flow, trapping piranhas. Gutting and cleaning of fish along the banks or on bridges and tossing the entrails makes a feeding regimen for piranhas. Lastly, the breeding cycle of piranhas could also provoke attacks, since it is well established  that piranhas protect their eggs and young.

ABSTRACT

Cohen, Miles, A.; Beaumont, William, R. C.; Thorp, Natalie, C. 1999

Environmental Biology of Fishes 54(1): 45-52

Adult black piranhas, Serrasalmus rhombeus, were radio-tracked using purpose built equipment in the 2.6 km long oxbow lake Coco Cocha, south east Peru during a five month period in the dry season of 1995. Fish were tagged externally in front of the dorsal fin. S. rhombeus showed generally localized movements in different sections of the lake with only one making use of its whole length during the tracking period. S. rhombeus in the shallower extreme sections of the lake were seen to make frequent trips into flooded forest. Speed plots and perceived activity plots revealed cyclic patterns of movement and activity synchronized with dawn. Those fish tracked at night were active until after dark and sometimes throughout the night into the early hours of the morning.

COMPLEX FORMS

VIEW VARIOUS GEOGRAPHICAL FORMS OF RHOMBEUS COMPLEX. CLICK HERE.

Sometimes referred to by hobbyists as a true black piranha, this name is nonsense since many species of piranhas (for example; S. spilopleura) are referred to by natives as Black Piranha in the locality from where they are found. The dark color is very common among older piranhas and those in breeding condition. It is quite possible this hobbyist referral to a true black piranha might loosely refer to the old placement of S. niger to these species. However, like the original S. niger description, this usage of the term; true black piranha, is erroneous. S. rhombeus is an enigma to taxonomists to this present day. Many species located in S. America were placed as other species rather than S. rhombeus (such as; S. hollandi, S. gymnogenus, S. aureus, etc.) based on juvenile forms or breeding forms (of S. rhombeus) without taking into account the number of specimens needed to better catalog them as an actual distinctive species.  However, the situation itself is much more complex than that, as is the species identification, particularly among juvenile fish. While it is discussed below, the rhombeus-complex group is still being looked at by competent authorities today. The variety of body shapes, coloration, and size is confusing. However, as stated below the consistency and trait of the species is the eye color, always a rich lake (red) at maturity. Below, further discussed (provided by a link) is the various geographical forms presented by George Fear. Historical authors placed this species as a Pygocentrus because of the adult form and lack of palatine teeth (worn off). In reviewing photographs from hobbyists and samples sent to me, many of the fishes sold purported to be S. rhombeus have largely been member of the compressus group. In rare occasions, S. sanchezi has been sold as S. rhombeus because of the similarity at juvenile sizes. So it is my suggestion, hobbyists need to review the material here at OPEFE and compare their fishes to the photos provided.

The problem of rhombeus nomenclature and description is a big one. There are several forms widely distributed. The form living in the Guiana's are slender, while forms living in the Orinoco, Amazonas and other South American rivers are deeper and very dark. The only thing common is that they have a red eye. Scientists believe that S. rhombeus is a complex of species. Both Dr. W.L. Fink and Dr. Antonio Machado-Allison are still working with the Brazilian species. According to Nakayama et al (unpubl) fishes from Catalão Lake (a mixed water ecotone) which is formed by water from the Solimões River (white waters) and the Negro River (acid and dark waters), this environment caused  some changes in chromomsomes in this species. This melting together (or fusion) of the centromere (=the centromere consists of fibres and holds together two to create a chromosome) by the eggs released by these species may have been caused by interbreeding. In previous discussions with a field researcher (1995) I discussed this topic of Serrasalmus species (in particular S. spilopleura) interbreeding and new populations forming after being cutoff from main rivers. At that time he thought it was unlikely. This new DNA information is changing this perception.

There seem to be several complex forms which vary in coloration and spotting. The distinctive red eye is present on all of them after some reach 5 inches or larger in sizes, some could be smaller in size. Their body color varies from silver to black with spotting variable at all ages. The anal fin has a reddish tint, later during ontogeny progressing to hyaline. A dark black margin on the anal fin is present on young specimens, later fading in intensity on adults. I have seen S. rhombeus belly colors also go through many ontogeny changes, from red, pink, yellow, gold to white. With maturity, the belly color may become black or white, with the upper body dark gray giving it a marbled appearance.

The white color often attributed to the species S. rhombeus was based on a juvenile form, however, water conditions can produce this effect on adults. The South American Indians are the folks generally responsible for providing common names and Piranha Branca (white piranha) is one of them. As Petry mentioned above it is only natural the darker forms of rhombeus would be called Piranha negra (black piranha) by natives. The common name itself has no scientific value and the Indians use this name on quite a few number of dark piranhas without discriminating the species it is. Presently, some species are being offered as Araguaia or Xingu "rhombeus." I have been afforded the opportunity to examine some of these species and most appear to be Serrasalmus rhombeus. There might be some variation to spotting and elongation of the body, but the majority seem to be this species. No systematist has yet to publish otherwise. 

IN THE AQUARIUM

Recommend keeping as solitary species in home aquarium. Large specimens like the one above should be kept in dimly lit aquariums. These larger one's inhabit deep waters where sunlight is less likely to penetrate. They are river fish and require strong current. I further suggest keeping them in a deep square tank than a long tank. Dimensions should allow sufficient turn around for the fish so that it will avoid bent tail syndrome, a feature seen on some fishes where the bottom or top of the caudal fin is crooked. This sometimes occurs from a fish being kept in a container that is to small for the fishes requirements. A power head is a must for flow and to keep the fish healthy! Water temperature should range from 76-82F. Soft, slightly acid preferably between pH 6.8 to 7.4. In a topic further below, I have included additional information on water chemistry reader's should consider.

When one considers the size of the aquariums that were successful, you are looking at having as a minimum 800g to over 1500g tanks. Or at the extreme, a large pool of water that is environmentally controlled. Could it be possible to breed this species in a smaller aquarium? As of this date, no hobbyist has reported such success. It might be possible one day to use a smaller tank (500g), but not likely. But until that day happens, let us stay within realism as much as possible. So, lets go by the assumption you have a monster tank of 800g's or more (even 800g is small but a good starting point). One of the key elements in such a tank would be a water drip method and wet/dry system for filtration. Water chemistry for this species is variable as its body morphology. So if you have one of the many different body shapes and localities of S. rhombeus, it might be prudent to research the water your fish comes from, if you know. Otherwise here are some suggestions: 

1. Rio Xingu: High water; Temperature 80ºF pH 6.7 6.9

2. Rio Araguia: pH 5.8-7.5 (6.5), 4-20 dH (8), 72-82°F (22-28°C)

3. Rio Negro and Orinoco rivers: pH: 4.5-7 (6.0); 2-8 dH (6); 75-82°F (24-28°C)

In attempting to breed this species use the midline parameters of pH and temperature. The successful breeding of S. rhombeus at the Duisburg Zoo (Aquarium Zoological Gardens) Germany was accomplished in the evening hours 1900-2000 hrs(7pm to 8 pm). The large (1200g) tank was densely planted with Cryptocoryne sp., Echinodorus, Aponogeton, and Vallisneria. They appeared to defend the eggs. Water temperature for the 1200g tank ranged from 20-25ºC (68-77ºF), extra soft (ion exchanger), filtered over Ehfi substrate (coarse) and granulated lava material. The eggs were layed in dense moss (1500 or more eggs) at a root of a tree on that first occasion. After the fry developed and were a year old (they had been removed from the parent tank), some were returned to the parents tank and swam side by side peacefully with no problems. The adult fish spawned again in 1964 and 1965. The spawn was left in the tank and it was devoured. Once the group of young fish (the one year olds) reached  about 15 cm (6 inches) in length, they turned on each other and reduced their number. The attacks were mostly from the parent fish. It remains unclear how many were left alive.

GROWTH RATE

The Wharf Aquarium (Old Fishermen's Wharf) in Monterey, California housed 2 large specimen's of two species. The previous owner (and biologist) Nelson Bill Hyler, confirmed the other species being red-throated S. sanchezi  after I provided a photograph to him and his own recollection of the fish having a bright red throat and brilliant scales. The year was 1957, and my seeing those fish for the first time impacted my life forever. It was also the trigger to make piranha studies for me, a life-long project. I had the opportunity to speak with Bill, circa 1997, his daughter Joanie operates the now known as The Wharf's General Store.

It was interesting to find out this elderly gentleman could remember those piranhas so clear in his mind. That information was extremely helpful to me and I credit Hyler and his piranha display for giving me the idea to start OPEFE. I hope most of you will get an opportunity to visit their store and the elegant City of Monterey. Later I would visit the Steinhardt Aquarium in San Francisco, that same year and seeing my first school of Pygocentrus nattereri, my journey studying  piranhas begins.....

WHY THE SLOW GROWTH RATE?

S. rhombeus are found in fast water, mostly at eddies below rapids in rushing waters or in places with faster flow if there aren't any rapids.  Growth reduction in captivity is likely associated to poor diet, thus feeding the whole fish and other vitamin and protein rich food should take care of the problem.  The other aspect is the relative size of the tanks in which they are kept, and thus the quality of the water.  As stated, they are probably fairly sensitive to dissolved ions and that could be a factor that reduces growth. 

Always remember that they live in very soft, nutrient poor waters to begin with, and thus are physiologically adapted to those conditions.  Any departure from that will cost energy to regain osmotic and physiologic balance. Growth is largely dependent on nutrition and environmental factors, thus captive fish may not grow as large because of tank stress issues, but usually they do if a drip system is used which would help replace water.

The record for S. rhombeus is 7 lbs and a fraction, that is a big piranha. A  37.4 cm in length (almost 14 3/4 in), may weigh  5 1/2 lbs.  7 lbs fish are close to 16 inch if not more.

STEALTH  AND FOOD

The wash out in white color for certain S. rhombeus probably works as a stealth mechanism, you don't want to be black there, either as a prey or a predator. Many fish do this when in different habitats. The species is a fin-eater, though it will eat whole fish on occasion if the opportunity is there. Most bites reported are from careless handling of the fish (see ATTACKS ON HUMANS) .

The largest wild caught examples  reported by fishermen average 50.0 cm or larger is common. Some foods these fish eat include: 82.0% finfish, bony fish (juv./adults); 11.0% terrestrial plants fruits/seeds; 7.0% zoobenthos benth. crust. crabs (juv./adults) source: (Machado-Allison, Goulding). Juveniles inhabit areas that are tranquil with abundant vegetation. Here they feed on micro crustaceans and aquatic insects. Later, as adults, leave the protection of the vegetation to live out their lives feeding principally on fins, parts of fish or whole in deeper waters and in rapids.

PET STORES

Pet stores generally lump piranhas into a color name if they are not sure what species it is. Some situations, the wholesaler already has the fish marked as a certain species under a scientific name without really being certain that it is that species. The problem is further grossed out given the quality of information of the piranha books published in the last 40 years which these dealers use for guidance. The truth of the matter is the average pet store doesn't know what piranha species they are selling and it is only recently that this situation has improved by people visiting hobbyist piranha forum like Piranha Fury. 

SCIENCE

Pygocentrus caribe described by Valenciennes in Cuvier and Valenciennes (1850)(as a Serrasalmus), apparently to provide binomial for the species description published by Humboldt and Valenciennes (1821); See P. cariba. Valenciennes apparently did not recognize the use of cariba in the figure caption in that work as a proper christening of the species. Considered a synonym of cariba herein; most authors, following Eigenmann (1915) have considered it a synonym of S. rhombeus. (FINK, 1993).

Pygocentrus normanni, described by Géry (1964) in Taddyella, based on a specimen of Serrasalmus rhombeus from Surinam (Géry, 1972). Type not seen, but the figure from the original description is clearly a Serrasalmus. (FINK, 1993). In this species, the suborbital covers the opercle when the fish is still young (100 mm or slightly more). Some of the species grow to a huge size (450 mm SL) at which time they are almost black.  S. rhombeus does travel in more or less small groups of the same species. But this is not a regular occurrence. The species is almost always solitary in contrast with the true piranhas, preferring to hunt and travel alone. A humeral spot is present on most geographical forms of S. rhombeus. However, this fades with the dark ground color as the fish matures. This blemish may be very faint or prominent depending on locality of collection.

Pygocentrus (Serrasalmus niger): The reader can visit THIS PAGE for more information about S. niger. The only known photograph of a live S. niger known to me is the following from the Aquarium Journal, January 1955. According to the cover photograph caption "The first specimen of Black Piranha Serrasalmus niger Schomburgk, ever exhibited  alive in the U.S.A. It is the 11 inches long, and is now in the preserved fishes collection of the Natural History Museum, Stanford University, No. SU 19417."

DnA

Updated information (Numerical updates, highest number is current status). Please use the cited references below to read the entire article:

2. Recent studies on Amazonian Serrasalmus species have revealed karyotypic divergence between and within populations of S. spilopleura and Serrasalmus rhombeus (Nakayama et al., 2000, 2001, 2002; Centofante et al., 2002). Nakayama et al. (2001) has suggested that S. rhombeus cryptic species may exist based on the two cytotypes (2n = 58 and 2n = 60) found at Lake Catalão located near the confluence of the Negro and Solimões rivers in the Brazilian state of Amazonas. In addition to being identified by their karyotypes (Nakayama et al., op. cit.) fish belonging to the S. rhombeus complex are also moderately distinguishable by parasite analysis (Van Every and Kritsky, 1992) but not by their 16S mitochondrial DNA (Ortí et al., 1996) but as yet there have been no isoenzyme studies on this complex. The new S. rhombeus cytotype reported here for the first time, 2n = 60 B (44M-SM+4ST+12A) revealed monomorphism for the presumably fixed allele Est-D3³, and was detected in all four S. rhombeus specimens examined, although this allele can only be definitively reported as fixed following the screening of the Est-D3 locus in a larger population of the S. rhombeus 2n = 60 cytotype. Gradual frequency differences in the A*125 and B*210 alleles at two GPI loci detected in S. spilopleura caught between the upper Paraná River (cytotype 'a') and the lower Paraná River (cytotype 'b' and cytotype 'c') led Cestari (1996) to suggest that there may be interbreeding between fish from these two sites, supporting the hypothesis of a hybrid origin for the 'c' cytotype. However, our esterase-D and chromosome data do not support the existence of different S. rhombeus piranha species in Lake Catalão and there was no indication of hybridization among the S. rhombeus cytotypes examined. Thus once cytotype-specific fixed alleles are detected in any S. rhombeus isoenzyme patterns different taxonomic units with species status will have to be formally recognized. (Aylton Saturnino Teixeira et al.,)

Karotype and Nucleolar Organizer regions in Serrasalmus rhombeus (Serrasalminae) from Caicara Del Orinoco, Venezuela.

M. Nirchio, A. Granado, E. Ron, and J. E. Perez.

HISTORICAL SCIENTIFIC NAMES

• Salmo rhombeus Linnaeus, 1766. Syst. Nat. ed. xxii, i:514.

• Serrasalmus rhombeus Lacepede, 1803, Hist. Nat. Poiss, 5:283-234.

• Serrasalmus (Taddyella) normani (Géry, 1964, Vie et Milieu, 14(3): 609-615, Fig. 4.

• Pygocentrus pyraya Epithet misspelled (not from Cuvier) Popta, 1914.

• Pygocentrus nigricans (not from Spix) Müller and Troschel, 1844.

• Pygocentrus niger (not from Schomburgk or from Müller and Troschel) Valenciennes, 1849).

• Serrasalmus boekeri Ahl, E.,Sitzungsberichte der Gesellschaft Naturforschender Freunde zu Berlin, 3/1/31, Diagnosen einiger neuer südamerikanischer Süßwasserfische., Ahl, E. . 1931 Sitzungsber. Ges. Naturf. Freunde Berlin. 1930(Oct-Dec):405-409.

DISTRIBUTION

Amazonas Basin, Orinoco Basin, North and Eastern Guiana Shield rivers, Northeastern Brazilian coastal rivers. Occurs in the rapids but is also captured in deep zones of main rivers. Sometimes found with S. manueli.

Contributors and Advisors

• Petry, Paulo

• Hyler, Joanie

• Hyler, Bill

REFERENCES

• Aylton Saturnino Teixeira; Celeste Mutuko Nakayama; Jorge Ivan Rebelo Porto; Eliana Feldberg, (2006) Esterase-D and chromosome patterns in Central Amazon piranha (Serrasalmus rhombeus Linnaeus, 1766) from Lake Catalão, Genet. Mol. Biol. v.29 n.3  São Paulo.

• Allendorf FW and Utter FM (1979) Population genetics. In: Hoar WS, Randall DJ and Brett JR (eds) Fish Physiology, v. 8. Academic Press, New York, pp 407-454.

• Alonso SK and Alfenas AC (1998) Isoenzimas na taxonomia e na genética de fitonematóides. In: Alfenas AC (ed) Eletroforese de Isoenzimas e Proteínas Afins. Editora da Universidade Federal de Viçosa, Viçosa, pp 525-539.

• Anti AB (2000) Caracterização de germoplasma de soja e de feijão através de eletroforese de isoenzimas da semente. Bragantia 59:139-142

• Norman, J.R. The South American Characid Fishes of the Subfamily Serrasalmoninae, with a revision of the Genus Serrasalmus Lacepède, 1929

• Schomburgk, Robert H. Fishes of British Guiana 2 Vols. In: The Naturalist's Library, edited by Sr. Wm. Jardine, vols. 30 and 31, London, 1843.

• Eigenmann, Carl H., The Serrasalminae and Mylinae, In: Annals of the Carnegie Museum, vol. 9, nos. 3 and 4, Pittsburg, Pa.

• Machado-Allison, Antonio and Fink, William., Los Peces Caribes de Venezuela, Diagnosis, Claves, Aspectos Ecologicos Y Evolutivos.

• Schulte, Wolfgang., Piranhas in the Aquarium, TFH Publications, NJ 1988 pg. 90-94.

• Géry, J. 1964 Contributions a l'étude des poissons characoïdes - 27: systématique et évolution de quelques piranhas («Serrasalmus»).. Recueil d'observations de zoologie...dans l'ocean AVie Milieu (Ser. C) Biol. Terr. 14(3):597-617. Name on fig.4 (p.611); description on p.612.

• Fink, W.L. 1993  Revision of the piranha genus «Pygocentrus» (Teleostei, Characiformes). Copeia 1993(3):665-687

• Dr. Arthur Topilow, 30 inch TL S. rhombeus, Jumbo Fishes For The Large Aquarium, TFH Publications, Inc. Is it a hoax?

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