The murky depths of the Amazon River harbor fish that are little known to science, which is why John Lundberg took his research team there this past year. In a 65-foot boat, Lundberg, an ichthyologist at the University of Arizona in Tucson, trawled over 2,000 miles of the Amazon, lowering his nets into water as deep as 50 feet and filling 33 large drums with fish—mostly catfish and electric fish. Those species do well in deep river channels because they don’t rely on sight but instead have special organs that detect the electric fields of their prey. There’s no light penetration beyond a few inches because there’s so much sediment in the water, says Lundberg. Even if they had eyes, they wouldn’t be able to see anything.
In all, Lundberg caught more than 375 species of fish, including about 35 new ones, bringing estimates of freshwater species in South America to around 5,000—about five times the North American total. Some of the weirder new species include tiny catfish less than two inches long, electric fish that feed exclusively on the tails of smaller electric fish, and a catfish with a fingerlike organ, probably electrosensitive, protruding from its chin. To have that many different kinds, says Lundberg, and then to have some of them so obviously specialized to live there—they live nowhere else—it’s kind of a surprise.