This species has been mistaken for P. yepezi from Lake Maracaibo (Rosa 1985). It is also mistaken for P. falkneri, P. signata, and P. castexi in the ornamental trade (Ross and Schäfer 2000). This species presents a great variation in colouration patterns, and it has been proposed that individuals from the upper part of the Magdalena basin (Embalse de Prado) differ from those from the lower part of the basin (Ortega-Lara pers. comm. March 2022).

The Magdalena Freshwater Stingray (Potamotrygon magdalenae) is a small (to 48 cm disc width) Neotropical freshwater stingray endemic to the Magdalena-Cauca and Atrato basins in northern Colombia. It is known only from freshwater habitats. It is heavily fished for the national and international ornamental aquarium trade, being one of the most highly traded freshwater rays from Colombia with juveniles captured for the ornamental trade. Adults are targeted and taken incidentally for human consumption. The Magdalena-Cauca and Atrato basins region has been severely impacted by habitat degradation and fragmentation in the past four decades due to dam construction, agricultural activities, deforestation, mining, and drying up of swamps and hydrological changes. Genetic population structure is apparent throughout the species’ range with the presence of geographic barriers that could isolate populations and decrease the resilience of the species. Thus, it is suspected that the Magdalena Freshwater Stingray has undergone a population reduction of 20–29% over the past three generation lengths (27 years) due to levels of exploitation and significant habitat degradation, and it is assessed as Near Threatened, close to meeting Vulnerable A2cd.

This species is endemic to Colombia where it is restricted to the drainages of some rivers, including the Magdalena, Cauca, San Jorge rivers (Magdalena-Cauca basin), and Atrato River (Atrato basin). It has been found in different areas of the middle (as El Llanito, San Silvestre and Paredes swamps, Bodega Central, Lebrija river, Puerto Wilches wetlands, Peruétano spout), high (Betania and El Prado dams) and low (Mesolandia and El Guájaro swamps) zones of the Magdalena-Cauca basin (Castellanos-Morales et al. 2011). It has not been reported in the Sinú River (Sinú basin).

The population size of this species is not known. Genetic studies reveal population structure throughout its distribution with the presence of geographic barriers. Population structure exists in five different localities of the lower (Mesolandia, Chimichagua and Ayapel) and middle (Paredes and Guarinocito) sub-basins of the Magdalena River, separated by three geographic barriers (Ramírez 2018). This genetic structure may decrease the resilience of the species to threats (Ramírez 2018).

The Magdalena Freshwater Stingray is regularly caught along the Magdalena Basin, especially in swamps and tributaries; and is less frequent in Atrato and San Jorge rivers. However, the species is subject to intense targeted fishing pressure for the ornamental trade and its habitat quality is declining. The Magdalena-Cauca basin has been severely impacted by habitat degradation and fragmentation for 80 years with hydrological changes throughout its range, and more recently (at least 20 years) by contamination by agrochemicals and heavy metals from mining. This has led to a reduction in the quality and availability of the habitat. It is suspected that the population has undergone a 20–29% reduction over the past three generation lengths (27 years) due to exploitation and a decline in habitat quality.

The Magdalena Freshwater Stingray is only known to date from freshwater habitats. It is demersal and occurs at depths of 0–59 m in the damps (Mejía-Falla et al. 2016). Its preferred habitat is muddy substrates in turbid, warmer and shallow waters, with currents of medium intensity, and with the presence of the “taruya” or “water buchon” (Eichhornia crassipes), or without any type of vegetation on the surface (Mejía-Falla et al. 2016). The relative abundance of this species is negatively correlated with depth and positively with bottom temperature, but not with pH, conductivity, or dissolved oxygen (Mejía-Falla et al. 2016).

It reaches a maximum size of 48 cm disc width (DW) and 88 cm total length (TL) (Lasso et al. 2012). Lasso et al. (2013) reported that males mature at ~22 cm DW but Ramos-Socha and Grijalba-Bendeck (2011) reported minimum maturity size of 16 cm DW with median maturity size of 20 cm DW. There is variation in female size-at-maturity and fecundity among sub-basins of the Magdalena River with females mature at 14–26 cm DW, fecundity ranging from 1–10 pups, and size-at-birth ranging from 8–10 cm DW. In the Upper Magdalena River, females mature at the larges size of 26 cm DW with 7–9 pups (possibly 10) (Lasso et al. 2013). In the Middle Magdalena River, females mature at the smallest size of 14 cm DW with 1–10 pups and size-at-birth of 8.0–8.5 cm DW (Mejía-Falla et al. 2016, Pedreros et al. 2016). In the lower Magdalena River, females mature at 17–24 cm DW with 1-5 pups and size-at-birth of 8.7–10 cm DW (Teshima and Takeshita 1992, Ramos-Socha and Grijalba-Bendeck 2011). Reproduction is viviparous with probably a continuous reproductive cycle (Mejía-Falla et al. 2016). There are no age parameters available for this species, however, generation length was estimated as 9 years based on estimates of age parameters from related genera and families, that is, Potamotrygonidae, Dasyatidae, and Urotrygonidae (Lucifora et al. 2022). Biological and ecological information is not available for the Atrato basin.

The Magdalena Freshwater Stingray is subject to heavy targeted fishing pressure for the ornamental trade and for human consumption. It is also captured incidentally by small-scale subsistence fishers. For the ornamental trade, it is captured with pots or cast nets and for consumption it is mainly caught with gillnets and in some cases with longlines. Mejía-Falla et al. (2016) recorded that only 4.6% of the fishers engage in targeted catches, but 100% of the fishermen have incidentally caught this species in their fishing operations. Although the demand for consumption of this species is not high and is local, the number of inhabitants along the Magdalena River has increased, as well as the number of fishers, so this may indirectly represent an increase in the effort fishing on this species.

Despite the species wide distribution along the rivers and tributaries, its fishing for the ornamental trade is restricted to a few bodies of water in the lower Magdalena-Cauca basin, such as the Guájaro reservoir and the Mesolandia swamp, Atlántico. The ornamental trade of the Magdalena Freshwater Stingray, both national and international, is based on juveniles, which have high mortality rates in the marketing process and during rearing in aquaria (Mejía-Falla et al. 2016). In addition, the lack of knowledge of population trends of this species have prevented the structuring of a mechanism for sustainable use based on supply and not on international demand, as is currently the case. In 2019, Resolution 434 established an annual quota of 9,000 individuals of Magdalena Freshwater Stingray for the ornamental trade. The quota is based on demand, rather than on the biological and population information of the species, which can be counterproductive for the species. In 2021, this export quota was temporarily halted (Resolution 1134 de 2021, National Authority for Aquaculture and Fisheries), resulting in the temporary suspension of authorizations for the exportation of ornamental species as a precautionary measure.

The species is subject to numerous environmental and anthropogenic threats throughout its distribution leading to a reduction in the quality and availability of habitat. This is due to deforestation, erosion, water pollution from agrochemical, domestic (sewage) and mining activities, and wetland desiccation (Lasso et al. 2012). Hydrological changes have occurred throughout its distribution; drought problems in various regions of the basin that affect bodies of water where the species inhabits, have led to the local absence of individuals of the species, and even to the transfer of individuals between bodies of water by fishers from the lower basin of the Magdalena River (Mejía-Falla et al. 2016). Dam construction (since 1980) is also a threat because it creates barriers to the species' dispersal and interrupts the genetic flow (Mojica et al. 2012).

The Magdalena Freshwater Stingray is valued in the national and international ornamental aquarium trade and between 2003–2012 was the first or second most exported Potamotrygon species in Colombia (Sánchez-Duarte et al. 2013). Juveniles of this species are mostly used in the ornamental trade. Traders consider that there are two morphs (red and black) of the species in the Magdalena basin, but only the black ones (lower basin) are of interest for the ornamental trade. The meat of adults is also used for human consumption, although consumption is occasional, local, and mainly in the upper basin (i.e., Betania reservoir) (Mejía-Falla et al. 2016). At some times of the year when fishing for other species is very low, adults of the Magdalena Freshwater Stingray are captured for subsistence use (Lasso et al. 2012, Mojica et al. 2012).

The Magdalena Freshwater Stingray is subject to a number of conservation resolutions in Colombia. It is included in the National Action Plan for the conservation and management of sharks, rays and chimaeras of Colombia (Caldas et al. 2010) as a species of very high action priority, in relation to its fishing, trade and distribution. In 2015, the National Authority for Aquaculture and Fisheries (ANUAP) introduced a Resolution (1924) for ornamental fish species that includes the Magdalena Freshwater Stingray and which mentions the AUNAP must take the management measures it deems necessary for its use or restriction and/or recommend to the Executive Committee of fishing to establish an annual quota for its use. A quota for this species was defined in 2019.

In 2017, Resolution 1609 prohibited the capture, storage, transport, and trade of females of the Potamotrygonidae family that are pregnant and established that only a disc width of 15– 20 cm could be traded for 10 species of the family Potamotrygonidae (including Magdalena Freshwater Stingray). However, individuals of the Magdalena Freshwater Stingray between 15–20 cm DW in the lower and middle sub-basins of Magdalena-Cauca basin could be pregnant and be traded (due to a lack of knowledge of its pregnant state by the traders). In 2021, this export quota was temporarily halted (Resolution 1134 de 2021, National Authority for Aquaculture and Fisheries), resulting in the temporary suspension of authorizations for the export of ornamental species as a precautionary measure to contribute to its management and protection.

The Potamotrygonidae were listed under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix III in 2017 mainly to improve trade data. Colombia has included the family Potamotrygonidae under Appendix III. Species and quantities reported to CITES have errors in terms of reported country of origin, quantities, and species identifications (J. Araujo and P. Charvet pers. obs 2021). Further research is needed on population size and trends, and life history, and catch rates should be monitored.