Charax awa: A new species of Charicid Fish from Maranhão State in northestern Brazil.

Charicids are freshwater Boney Fish related to Piranhas and Tetras that are found across South and Central America and as far north as Mexico and parts of Texas. Members of the genus Charax are medium sized members of this group, reaching a maximum of about 130 mm in length, most abundant in the Andean regions, but also found in southern and western Brazil and parts of the Guyanan Shield. No described member of this genus has a distribution that includes the coastal basins of northeastern Brazil, but there are several records of Fish apparently belonging to this group being found there. 

In a paper published in the journal Zoosystematics and Evolution on 1 February 2018, Erick Cristofore Guimarães of the Programa de Pós-Graduação em Biodiversidade e Conservação, and the Laboratório de Sistemática e Ecologia de Organismos Aquáticos at the Universidade Federal do Maranhão, Pâmella Silva De Brito of the Programa de Pós-Graduação em Biodiversidade e Biotecnologia da Amazônia and the Laboratório de Sistemática e Ecologia de Organismos Aquáticos at the Universidade Federal do Maranhão, Beldo Rywllon Abreu Ferreira, also of the Programa de Pós-Graduação em Biodiversidade e Conservação at the Universidade Federal do Maranhão, and Felipe Polivanov Ottoni, of the Programa de Pós-Graduação em Biodiversidade e Conservação, the Programa de Pós-Graduação em Biodiversidade e Biotecnologia da Amazônia, the Laboratório de Sistemática e Ecologia de Organismos Aquáticos, and the Programa de Pós-Graduação em Oceanografia at the Universidade Federal do Maranhão, describe a new species of Charax from the Rio Mearim, Rio Munim and Rio Turiaçu basins, of Maranhão State in northestern Brazil.

The new species is named Charax awa, where ‘awa’ is the name used by the Guajá people of Maranhão State to describe themselves. Adults of this species range from 40.2 to120.0 mm in length and are silvery in colour, darker on the upper surface and towards the front, and with blotchy markings on the fins. The upper part of the head is distinctly concave, and the eyes somewhat small. The upper and lower jaws both have enlarged canine teeth as well as rows of smaller, conical teeth. 

 Charax awa, live specimen from a stream at the Miranda do Norte, in the Mearim River Basin of Maranhão State, Brazil. Erick Guimarães in Guimarães et al. (2018).

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Myloplus zorroi: A new species of Pacu from the Rio Madeira Basin of Brazil.

Pacus, Myloplus spp., are Characiforme Fish closely related to Piranhas, found in the rivers of South America. They are highly specialized herbevores consuming nuts and hard seeds, which they crush with a double row of molar-like teeth that run across the front of their jaws.

In a paper published in the journal Zookeys on 7 March 2016, Marcelo Andrade of the Laboratório de Biologia Pesqueira e Manejo dos Recursos Aquáticos and Programa de Pós-Graduação em Ecologia Aquática e Pesca at the Universidade Federal do Pará, Michel Jégu of the Institut de Recherche pour le Développement, Biologie des Organismes et Ecosystèmes Aquatiques at the Institut de Recherche pour le Développement and the Laboratoire d´Icthyologie at the Muséum national d’Histoire naturelle and Tommaso Giarrizzo, also of the Laboratório de Biologia Pesqueira e Manejo dos Recursos Aquáticos and Programa de Pós-Graduação em Ecologia Aquática e Pesca at the Universidade Federal do Pará and of the Programa de Pós-Graduação em Biodiversidade e Conservação, again at the Universidade Federal do Pará, describe a new species of Pacu from the Rio Madeira Basin of Brazil.

The new species is named Myloplus zorroi, in honour of the ichthyologist Mauricio Camargo-Zorro of the Instituto Federal de Educação, Ciência e Tecnologia for his work on the Fish of the Marmelos Conservation Area, and also inrefference to the fictional character Zorro, who wore a mask to conceal his identity. It is unusually large for a Pacu, reaching 351.1 mm in length and 62.5 mm in depth, and has a number of unusual features, notably the absence of an abdominal keel and of the fused prepelvic spines which form a serrae (saw-like structure) in other Pacu, differences that initially led to the species being identified as a member of the related genus Tometes, though examination of its teeth eventually led to it being placed in the genus Mylopus.

Myloplus zorroi, female (a) and male (b). Andrade et al. (2016).

Myloplus zorroi was found living in moderate to fast flowing rivers with rocky or sandy bottoms in the Rio Madeira Basin, part of its range falling within the Campos Amazônicos National Park (formerly known as the Marmelos Conservation Area).

 Corredeira dos Periquitos, Rio Aripuanã, type locality of Myloplus zorroi, Rio Madeira Basin,
Brazil. Andrade et al. (2016).

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African Tigerfish observed snatching Barn Swallows from the air.                                   A variety of Fish are known to occasionally take Birds as prey. Sharks and other large carnivorous marine...

A new species of Characiforme Fish from the Congo Basin.

The bite of the Megapiranha.                  Piranhas are carnivorous Characid Fish from the Amazon river basin with a reputation for stripping large animals to the bone in seconds. While this reputation...

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African Tigerfish observed snatching Barn Swallows from the air.

A variety of Fish are known to occasionally take Birds as prey. Sharks and other large carnivorous marine Fish will frequently feed on Seabirds on the water surface, and in freshwater aquatic environments Bass, Eels, Piranhas, Pike and Catfish have all been observed to take avian prey, either from the water surface, from land close to the water, or from overhanging vegetation. Uniquely, the African Tigerfish (Hydrocynus spp.) has a reputation for taking Birds on the wing; this has been reported by numerous authors from 1945 onwards, but these reports have all been based upon anecdotal evidence, never witnessed by the authors themselves as part of an organized study.

In a paper published in the Journal of Fish Biology on 19 December 2013, Gordon O’Brien, Francois Jacobs, S Evans and Nico Smit of the Water Research Group (Ecology) at the Unit of Environmental Sciences and Management at North-West University report direct observation of feeding on Birds in flight by a population of the African Tigerfish (Hydrocynus vittaltus) at Schroda Dam, an artificial lake in the Mapungubwe National Park in Limpopo Province, South Africa.

The Shroda Dam was constructed in 1993 as a storage lake, and covers 4 100 000 m³. The African Tigerfish (Hydrocynus vittaltus) was deliberately introduced to the lake in 2003. The lake is considered to be nutrient poor compared to typical Hydrocynus vittaltus environments, and the Fish spend a higher proportion of their time foraging than has been reported in other populations. However they typically avoid open waters during the hours of daylight, probably due to the presence of the African Fish Eagle (Haliaeetus vocifer).

In February 2011 a number of Fish that had been radio-tagged as part of a study into their behaviour were observed to be breaking this taboo, and becoming highly active in open waters during the mid-morning. Direct observation of the lake revealed that the fish were striking at Barn Swallows (Hirundo rustica), a migratory Bird which visits the lake seasonally, both drinking on the wing and hunting small Insects close to the water surface. None of the radio-tagged Fish was observed capturing a Barn Swallow, though other Fish were on numerous occasions, and some instances were filmed with a hand-held camcorder.

The Tigerfish employed two different strategies when hunting Birds. Some Fish chased the Birds at the surface prior to striking, while others remained deeper in the water and suddenly lunged upwards at Birds. This second hunting behaviour was more successful, capturing a Bird on roughly one-in-three attempts (as opposed to about one-in-seven for the chase and lunge technique), but involved compensating for light refraction at the water surface, something not all the fish appeared able to do.

Avivorous behavioural strategies adopted by Hydrocynus vittatus in the Schroda Dam man-made lake. (a) Flight path of the prey Hirundo rustica, (b) surface pursuit strategy of Hydrocynus vittatus to overcome surface image shift due to light refraction (angle θ) and (c) direct aerial strikes by adult Hydrocynus vittatus that compensate for the image shift (not drawn to scale). O’Bien et al. (2013).

Since the Shroda Dam is a new environment for the Tigerfish, and fast-moving Barn Swallows are a fairly difficult Bird to target from the water, O’Brien et al. suggest that this behaviour is likely to be quite widespread in Tigerfish, and that it would be worth investigating at other localities.

See also…

 A new species of Characiforme Fish from the Congo Basin.

 Terrestrial hunting in European Catfish.

Catfish (Siluriformes) are a large, diverse group of freshwater and shallow marine Fish, found on every continent except Antarctica. They are primarily benthic detrivores, but show a very wide rage of trophic adaptations. They show the widest range of sizes of any group of Boney Fishes, with the smallest species...

 The bite of the Megapiranha.

Piranhas are carnivorous Characid Fish from the Amazon river basin with a reputation for stripping large animals to the bone in seconds. While this reputation is unquestionably exaggerated, Piranhas are still formidable predators, capable of delivering powerful bites and tackling large prey. In the Late Miocene South America was home to a much larger fish, Megapiranha paranensis, which is thought to have...

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A new species of Characiforme Fish from the Congo Basin.

The Characiformes are a group of freshwater Fish from Africa and South America. They are most numerous in South America, where the group includes Freshwater Barracuda, Characins, South American Darters, Tetras, Trahiras, Freshwater Hatchetfish, Hemiodontids, Pencil Fish and Piranhas. African Characiformes include Lutefish, African Pike, Congo Tetras, African Tigerfish and Distichodontids. The group appear in the fossil record in Brazil in the Early Cretaceous, and apparently diversified during the Cretaceous and spread to Africa before the break-up of Gondwana, though their fossil record is not extensive.

In a paper published in the journal Zootaxa on 31 July 2013, Melanie Stiassny of the Department of Ichthyology at the American Museum of Natural History, John Denton of the Department of Ichthyology and Richard Gilder Graduate School at the American Museum of Natural History and Raoul Monsembula Iyaba of the Département de Biologie at the Université de Kinshasa describe a new species of Distichodontid from the Congo Basin of Central Africa.

The new species is placed in the genus Eugnathichthys, and given the specific name virgatus, meaning banded or streaked, a reference to its colouration. Like the two previously described members of this genus, Eugnathichthys virgatus is a specialist fin-feeder; it survives by biting chunks from the fins of larger Fish and consuming them. 

Eugnathichthys virgatus was discovered during a genetic study of populations of fish of the genus Eugnathichthys. It is essentially a cryptic species, resembling closely Eugnathichthys macroterolepis, but found to be a separate species by genetic analysis. Eugnathichthys virgatus inhabits the Lengoué and Lomako Rivers, while Eugnathichthys macroterolepis inhabits the Nsele and Kasai Rivers.

Eugnathichthys virgatus is an elongate Distichodontid Fish with powerful jaws. It is banded on its dorsal surface, though this banding is relatively inconspicuous except close to its midline. Its fins are orange, with distinct darker bands. Eugnathichthys virgatus reaches 106 mm in length.

Eugnathichthys virgatus. Stiassny et al. (2013).

See also Terrestrial hunting in European Catfish, A new species of Catfish from Minas Gerais State in southeast Brazil, Two new species of Armored Catfish from Columbia, The bite of the Megapiranha and A new species of Spotted Barb from the southern Western Ghats, India.

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