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ANDY MURCH ELASMO GEEK

 

WHAT IS ELASMODIVER?

Not just a huge collection of Shark Pictures: Elasmodiver.com contains images of sharks, skates, rays, and a few chimaera's from around the world. Elasmodiver began as a simple web based shark field guide to help divers find the best places to encounter the different species of sharks and rays that live in shallow water but it has slowly evolved into a much larger project containing information on all aspects of shark diving and shark photography.

There are now more than 10,000 shark pictures  and sections on shark evolution, biology, and conservation. There is a large library of reviewed shark books, a constantly updated shark taxonomy page, a monster list of shark links, and deeper in the site there are numerous articles and stories about shark encounters. Elasmodiver is now so difficult to check for updates, that new information and pictures are listed on an Elasmodiver Updates Page that can be accessed here:

WHAT'S NEW?

Shark picture - green sawfish

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Rosette River Stingray - Potamotrygon schroederi

All photographs copyright Andy Murch

View all available Potamotrygon schroederi Pictures in the shark picture database.

Common Names: Rosette River Stingray, Schroeder's Stingray, Columbian Ray, Sacha Ray, (and possibly) Chocolate Ray.

Other recorded names:

Guacamaya-Rochen - Germany German

Kukkajokirausku - Finland Finnish

Raya guacamaya - Venezuela Spanish

Rozetzoetwaterrog - Netherlands Dutch

Schröders Stachelrochen - Germany German

Schroeders Stechrochen - Germany German

Kolumbianischer Rochen - Germany German

Latin Name: Potamotrygon schroederi

Family: Potamotrygonidae

A note on the identification of South American Freshwater Stingrays. Dorsum patterns and colors are extremely variable among the freshwater rays of South America making positive identification using pattern and coloration alone extremely difficult. Some morphologically different species occasionally display an almost identical pattern and to make identification even harder there can be a degree of hybridization among sympatric species. Important characteristics to help the observer overcome these problems include the lateral markings on the tail, the presence or lack of raised denticles along the tail, the ratio of tail length to disc length, and the size and position of the eyes (although this last characteristic changes with age).

Identification: An extremely variable species even compared to other river stingrays. Some specimens exhibit clusters of spots that form flowerlike patterns on a plain or subtly mottled background. Flower patterns become smaller and more uniformly circular toward the edge of the disc. Other specimens display a dark reticulated pattern enclosing irregularly shaped light spots. There are endless intermediate color morphs. The tail is always patterned with distinct and regularly spaced dark bars. This is an important factor in positive identification.

Size: Maximum disc width 60cm

Habitat: South American river basins. 18-25 degrees C.

Abundance and distribution: Columbia to Brazil. Rio Apure (Orinoco basin) and Rio Negro (Amazon basin) and Rio Uaupes (northern Brazil) among others. Originally described from Venzuela (boca Apurito, Rio Apure).

Behavior:

Reproduction: Matrotrophic viviparity.

Observations:

Similar species: Where to start... Potamotrygon schroederi may be confused with many other South American river stingrays. It differs from P.yezepi in having regularly spaced bars along its tail. It can be distinguished from P.humerosa and P.dumerilii in having dark centers to its spots. P.scobina is also superficially similar but generally has more uniformly rounded markings.

Reaction to divers: Unknown but some South American freshwater rays are known to act aggressively when threatened. River stingrays are responsible for many injuries to wading fishermen.

Diving logistics: There are currently no organized opportunities to interact with freshwater stingrays but aquarist collecting sites include Paraguay, Peru, and Brazil.

Other diving locations submitted by readers:

References and further reading:

Aqualog Freshwater Rays. Richard Ross & Frank Schafer

Sharks and Rays Elasmobranch guide to the World. Ralf M. Hennemann IKAN

Fishbase.com

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