Essequibo



ID


310

Author(s)


Paulo Petry, Jennifer Hales


Countries


Guyana
Venezuela

Major Habitat Type


Tropical and subtropical upland rivers

Drainages flowing into


Atlantic Ocean


Main rivers to other water bodies


The main rivers of the ecoregion are the Cuyuni, Mazaruni, Potaro, Rupununi, and Essequibo.



Description

Boundaries

This ecoregion includes the entire Essequibo River basin in Guyana and part of southeastern Venezuela where it drains the eastern margin of the Guiana Shield (source at 600 m) and low country south of the Orinoco Delta.  The Essequibo is separated from the Caroní (Orinoco Basin) in the west and southwest and Branco (Amazon Basin) to the south by moderate divides of little more than 500 m elevation. It is also separated from adjacent small rivers of coastal Guyana by low divides of only a few meters. It is limited to the east by the drainage divide between the Essequibo and Demerara rivers.

Topography

The ecoregion encompasses a low coastal plain, forested hills, and highlands. Some of the ranges include the Pakaraima, Kanuku, and Acarai mountains, from which the Essequibo River rises. Elevations range from sea level to nearly 2400 m asl.

Freshwater habitats

The uplands include moderate gradient small streams and rivers with rapids and cataracts. Kaieteur Falls (251 m) on the Potaro River is impressive with a flow rate of 663 m³/s. Along the coastal plain are low gradient rivers, lakes, and swamps with seasonal flooding.

Terrestrial habitats

Moist forests cover a majority of the ecoregion, with marsh forests along rivers.

Description of endemic fishes

The Essequibo contains 58 endemic species including a handful of Rivulus species (Rivulidae), Bryconamericus hyphesson (Characidae), Lithogenes villosus, and Parotocinclus collinsae (Loricariidae).  Bryconops colaroja (Characidae) is endemic to the Cuyuní Basin (Chernoff & Machado-Allison 1999) and the monotypic Mazarunia mazarunii (Cichlidae) is known only from the Upper Mazaruni (Kullander 1990). Farlowella rugosa is near-endemic to this ecoregion and the Guianas [311]. Endemic genera are: Acanthocharax, Mazarunia, and Skiotocharax.

Other noteworthy fishes

The only goliath catfish that occurs in this ecoregion is the Laolau catfish (Brachyplatystoma vaillantii).

Ecological phenomena

The ecoregion contains the potamadromous barred sorubim (Pseudoplatystoma fasciatum).

Justification for delineation

This ecoregion lies in the Guyanan ichthyographic province outlined in Ringuelet (1975) and more broadly within the Guyanan-Amazonian ichthyographic  region (Gery 1969; Ringuelet 1975). It has a unique composition of endemic Guiana Shield taxa that are considered the most primitive sister groups to many fish taxa in South America.

Level of taxonomic exploration

Fair in larger rivers, still poor in headwaters and small streams.


References

  • Armbruster, J.W.,Sabaj, M.H.,Hardman, M.,Page, L.M.;Knouft, J.H. (2000). "Catfish genus Corymbophanes (Loricariidae: Hypostominae) with description of one new species: Corymbophanes kaiei" Copeia (4) pp. 997-1006.
  • Buitrago–Suárez, U.A.;Burr, B. M. (2007). "Taxonomy of the catfish genus Pseudoplatystoma Bleeker (Siluriformes: Pimelodidae) with recognition of eight species" Zootaxa 1512 pp. 1-38.
  • Chernoff, B. and Machado-Allison, A. (1999). "Bryconops colaroja and B. colanegra, two new species from the Cuyuní and Caroní drainages of South America" Ichthyological Explorations of Freshwaters 10 (4) pp. 355-370.
  • Eigenmann, C. H. (1909). "Reports on the expedition to British Guiana of the Indiana University and the Carnegie Museum, 1908. Report no. 1. Some new genera and species of fishes from British Guiana" Annals of the Carnegie Museum 6 (1) pp. 4-54.
  • Eigenmann, C.H. (1912). "The freshwater fishes of British Guiana, including a study of the ecological grouping of species, and the relation of the fauna of the plateau to that of the lowlands" Memoirs of the Carnegie Museum 5 (1) pp. 1-578.
  • Gery, J. (1969). "The fresh-water fishes of South America" E. J. Fitkau (Ed.) Biogeography and Ecology in South America ( pp. 828-848 ) The Hague: Dr. W. Junk.
  • Goulding, M. (1980). "The fishes and the forest: explorations in Amazonian natural history" Berkeley, CA: University of California Press.
  • Hijmans, R. J., S. Cameron and Parra., J. (2004) \WorldClim, Version 1.4 (release 3). A square kilometer resolution database of global terrestrial surface climate\ "<"[http://www.worldclim.org]">" (16 July 2009)
  • Hardman, M., Page, L. M., Sabaj, M. H., et al. (2002). "A comparison of fish survey made in 1908 and 1998 of the Potaro, Essequibo, Demerara, and coastal river drainages of Guyana" Ichthyological Explorations of Freshwaters 13 (3) pp. 225-238.
  • Köppen, W. (1936). "Das geographische System der Klimate" Köppen W. and R. Geiger (Ed.) Handbuch der. Klimatologie ( (Vol. 1, pp. 1–44 ) Berlin, Germany: Gebrüder Borntröger.
  • Kullander, S. O. (1990). "Mazarunia mazarunii (Teleostei: Cichlidae), a new genus and species from Guyana, South America" Ichthyological Exploration of Freshwaters 1 (1) pp. 3-14.
  • Lowe-McConnell, R. H. (1987). "Ecological studies in tropical fish communities" Cambridge, UK: Cambridge University Press.
  • Nijssen, H.;Isbrucker, I.J.H. (1986). "New records of the mailed catfish Planiloricaria cryptodon from the Upper Amazon in Peru, Brazil and Bolivia, with a key to the genera of the Planiloricariina" Bijdragen tot de Dierkunde 56 (1) pp. 39-46.
  • Reis, R., Kullander, S. and Ferraris, C. (2003) Check List of the Freshwater Fishes of South and Central America EDIPUCRS : Porto Alegre, Brazil
  • Ringuelet, R. A. (1975). "Zoogeografía y ecología de los peces de aguas continentales de la Argentina y consideraciones sobre las áreas ictiológicas de América del Sur" Ecosur 2 (1) pp. 1-122.
  • Schaefer, SA (1987). "Osteology of Hypostomus Plecostomus (Linnaeus), with a Phylogenetic analysis of the Loricariid Subfamilies (Pisces: Siluroidei)" Contributions in Science - Natural history Museum of Los Angeles County (394) pp. 1-31.
  • Vari, R.,C. Ferraris Jr., A. Radosavljevic;Funk, V.A. (2009). "Checklist of the Freshwater Fishes of the Guiana Shield" Bulletin of the Biological society of Washington 17