Freshwater Rays

Freshwater rays are cartilaginous fishes that are restricted to continental water bodies in South America. They are viviparous, have low fertility rates, slow growth and late maturation. These characteristics make them very vulnerable to anthropic pressures such as bycatch, and fishing for commercial consumption, and, most importantly, ornamental use.

Freshwater rays are of great national and international interest due to their demand in the aquariums market. Colombia is one of the major exporters of rays, making this market an important source of income at the local level for indigenous and rural communities in areas of low economic development. However, the exploitation of this market has developed without appropriate technical criteria to guarantee its sustainability. In addition, information about the biology, fishing, and population dynamics of species of freshwater rays is lacking. Therefore the Humboldt Institute has been working on increasing the amount of knowledge and making population estimates for this group of animals.

In South America there are 34 different species of rays. After Brazil, Colombia is the second country with greatest species richness of rays, having 11 registered species up to date; still new species are being discovered with the advent of research. In Colombia, freshwater rays are distributed in all of the basins and slopes of the Caribbean, but are not present in the rivers of the slopes of the Pacific. There is one endemic species, the Magdalena River Stingray, which is distributed in the Magdalena-Cauca basin and the Caribbean rivers(Atrato, Sinú, Canalete and San Jorge). The basins with the largest number of rays are those of the Amazon and Orinoco Rivers^1,2. Four out of the eleven species of rays in Colombia are found in the threat category of Vulnerable, being uncontrolled ornamental fishing their major threat³.

Currently, a species list and distribution data of freshwater rays exist in Colombia. Also, there is information on the biology, ecology, and fishing of some of the species and there have been advances in the methodology for developing population estimates⁴. Yet it is clear that more research is needed to identify and describe all species and also explore many areas.