Unique Fish of the Yucatan Peninsula

Underground rivers flow through the limestone bedrock underneath the Yucatan peninsula of Mexico. When a river enters a cavern it flows in a circular pattern, eroding the walls into a circular shape. The roofs of these caverns eventually collapse, creating a small bucket-shaped lake known locally as a cenote. There are almost 20,000 cenotes on the Yucatan peninsula, and they host many unique fish species found nowhere else on earth. A recent survey of 4 cenotes captured 1,350 fish including 11 species from 5 families. The cenotes studied were small and deep–less than 2 acres wide but over 30 feet deep.

The most common species found in this study were mosquito fish from the Poeciliid family. Cichilids were also common, most notably a beautiful fish, the yellow jacket cichlid. This fish is a popular game fish, reportedly with a good flavor. The yellow jacket cichlid has an interesting habit–it feigns death and preys on smaller fish that attempt to scavenge it. Colorful tetras, popular aquarium fish, live in cenotes, and they are preyed upon by the pale catfish, the top predatory fish in the studied cenotes. Scientists found blind swamp eels in these surveyed cenotes. Blind swamp eels are found throughout underground cave systems in the region and have no need for sight. Although some cenotes are connected to the ocean through underground passages, scientists found little marine influence on them. Instead, zooplankton and insect abundance along with phosphorus concentrations have a greater influence on fish populations.

View from inside a cenote. There are almost 20,000 of these geological features on the Yucatan Peninsula and they host fish species found nowhere else in the world. Photo from Thrillist.com.
Yellow Jacket Cichlid. A beautiful fish that is popular for catching and eating.
Blind swamp eel.
Pale catfish.

The Yucatan Peninsula was also home to an unique mammalian fauna during the late Pleistocene. Cenotes inundated by sea level rise preserved the remains of many species, including a species of giant ground sloth and a species of peccary found nowhere else. 4 complete human skeletons dating to the late Pleistocene were discovered in a cenote that is now below sea level. (See: yucatan peninsula | Search Results | GeorgiaBeforePeople (wordpress.com) )


Camargen-Guerra, T; L.K. Escalera Vazquera, L. Zambrano

“Fish Community Structure Dynamics in Cenotes of the Biosphere Reserve of Sian Kaan, Yucatan Peninsula”

Revista Mexicana de Biodiversidae


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