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More Than 200 Species Of Freshwater Fish Were Discovered In 2021

A report by Re:Wild and Synchronicity Earth revealed that over 200 species of freshwater fish were discovered in 2021, all new to science. While some were found in more obvious locations, others were found in more peculiar spots. 

Image of the Danionella cerebrum. Image Credits: Re:Wild & Ralf Britz.

More than 50% of all fish species on the planet are found in freshwater. However Harmony Patricio, the freshwater fish conservation program manager, explains: “When you look at the entire amount of water on our planet, only about 2-3% of that is fresh water. And of those 2-3% it’s only a fraction that is fresh water in rivers, smaller streams or lakes. . .So we have a tiny fraction of the world’s water volume harboring more than 50% of all fish species on this planet”. 

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The freshwater fish that the researchers discovered involved a variety of fascinating characteristics. One of the freshwater fish they found, named the Danionella cerebrum, was one of these fascinating discoveries. The Danionella cerebrum freshwater species boast a particularly unique feature. Rather than having a skull protecting the top of their brain, they instead have a thin layer of skin. This discovery is advantageous for researchers, who actively use the Danionella species for research in their neuroscience labs. 

Other interesting discoveries included a mysterious catfish with retractable ‘spikes’, located in the Xingu River basin. It has now been named the Wolverine Pleco due to the spikes that emerge from the catfish's gills as a defense mechanism. 

Image of the Wolverine Pleco catfish. Image Credits: Re:Wild & Leandro Melo de Sousa.

Researchers also found an unknown species of blind eel in a well in Mumbai, India. After pumping water from the well for three consecutive days, the researchers lowered a team member into the well, where they proceeded to make the fascinating discovery. This freshwater fish is coloured a blood-red, and is the first completely blind subterranean fish species known to exist in the Northern Western Ghats region. It has been named the Mumbai Blind Eel. 

Researchers have speculated that the Mumbai Blind Eel split from one of its closest living relatives over 1 million years ago. 

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