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Potamotrygon motoro

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA CHONDRICHTHYES RAJIFORMES POTAMOTRYGONIDAE

Scientific Name: Potamotrygon motoro
Species Authority: (Müller & Henle, 1841)
Common Name(s):
English Ocellate River Stingray
Synonym(s):
Potamotrygon pauckei Castex, 1963
Taeniura motoro Müller & Henle, 1841

Assessment Information [top]

Red List Category & Criteria: Data Deficient ver 3.1
Year Published: 2005
Date Assessed: 2005-10-01
Assessor(s): Drioli, M. & Chiaramonte, G.
Reviewer(s): Musick, J.A. & Fowler, S.L. (Shark Red List Authority)
Justification:
This assessment is based on the information published in the 2005 shark status survey (Fowler et al. 2005).

The Ocellate River Stingray (Potamotrygon motoro) is a freshwater ray and one of the seven nominal species of this genus inhabiting southern South America. Although this is the most abundant and widespread endemic ray species of the Parano-plata Basin, it is poorly known and its status is uncertain due to the sparse life history and population data available for this species. Further study and a new assessment in the near future is highly recommended, due to this species' limited geographic range and the major impacts to its freshwater habitat.
History:
2000 Data Deficient

Geographic Range [top]

Range Description: Rio Paraná, middle and lower reaches; Río Uruguay middle, Río de la Plata, Río Pilcomayo and Río Bermejo. Río Guapore, Río Negro, Río Branco, Río de Janeiro and Río Paraguay.
Countries:
Native:
Argentina; Brazil; Paraguay
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: This is the most abundant and widespread endemic ray species of the Parano-plata.
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: Like all river rays, the ocellate river ray is found in calm waters, especially on the sandy margins of lagoons, brooks and streams. They are most commonly caught when water levels are low (August-September and March-April in Río Paraná, Santa Fe region (Castex and Maciel 1965b)), and observed still and partly buried during the warmest period of the day (09.00-20.00). Fishermen also harpoon these rays during floods when they are found resting over vegetation in shallow water. Potamotrygon motoro catches coincide with a rise in water temperature (Castex and Maciel 1965a), with abundance increasing in the Paraná Medio from September to mid January, stabilising in early March, declining in April then disappearing (Martinez Achenbach and Martinez Achenbach 1976). It is possible that they remain permanently in the area, but are concealed on the bottom at other times. Martinez Achenbach and Martinez Achenbach (1976) consider that Potamotrygon species are ovoviviparous. Potamotrygon motoro reaches sexual maturity during its third year, at a disk width of 30-35cm. A specimen with a disk of 30 cm expelled nine foetuses immediately after being captured. Another, with a disk of 45 cm, gave birth to a litter of 15 young, eight females and seven males. The largest foetus was 13.5 cm in diameter and the smallest 9.5 cm. The diameter of the females was between 11-13.5 cm, whereas the diameter of the males ranged between 9.5-12cm. Female P. motoro were in an advanced stage of pregnancy in January (Castex 1963). Smaller females give birth to fewer young. The litter size is always odd, varying from 3-21 (Martinez Achenbach and Martinez Achenbach 1976).

According to Martinez Achenbach and Martinez Achenbach, plankton is the first food taken after birth. Juveniles complement their diet with small molluscs (Lamellibranchs and Gastropods), crustaceans and the larvae of aquatic insects. Fish of the family Loricaridae, Astyanax sp. and Pimelodella gracilis were found in the stomach contents of adults.
Systems: Freshwater

Use and Trade [top]

Use and Trade: Aquarium use

Threats [top]

Major Threat(s): All species of river stingray in the Parano-plata Basin have delicious meat and are harpooned by fishermen when seen in shallow water. Artisanal and commercial fishermen also catch some specimens on lines. The attractively patterned juveniles of this species are collected for the ornamental fish trade. The major threats to the species possibly derive from habitat degradation caused by the damming of the Río Paraná system for navigation and hydroelectric plants and the construction of many ports along the river.

Conservation Actions [top]

Conservation Actions: None.

Citation: Drioli, M. & Chiaramonte, G. 2005. Potamotrygon motoro. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 31 August 2014.
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