More than 300 fish species found in Madidi National Park

The Madidi National Park and Natural Integrated Management Area (PNANMI), in Bolivia, is among the most biodiverse areas in the world. Formed in 1995 in the upper Amazon River basin, the area has an extent of 18,958 km² and ranges in altitude from less than 200 m on the Amazonian floodplain to more than 6 000 m in the high Andes. It is home to an astonishing array of living creatures, including 5,535 species of plants, 1,633 species and subspecies of butterflies, and 1,830 species of vertebrates. 

In 2015, the Wildlife Conservation Society of Bolivia commenced an initiative, known as Identidad Madidi, to survey and record the plants and wildlife present in the National Park and Natural Integrated Management Area. They wished to ascertain whether the region was indeed the most biodiverse protected area in the world, as they suspected. In addition, they aimed to inform the people of Bolivia about their natural heritage by means of an educational campaign, as well as traditional and social media.  

With specialists from the Wildlife Conservation Society of Bolivia, the Institut de Recherche pour le Développement de Montpellier (France) and the National Museum of Natural History and the Ecology Institute of the Universidad Mayor de San Andrés, the Identidad Madidi team conducted fieldwork between 2015 and 2018. They visited 13 different sites and collected fish specimens by means of electrofishing, gillnets, trawls, line and hook, and ichthyoplankton nets (for fish larvae and eggs). 

The researchers have now published the results of their fish survey in the journal Neotropical Hydrobiology and Aquatic Conservation, where they report that the fish species list for Madidi now totals 333, more than double the number previously known from the region. In addition, the researchers suspect that as many as 35 of these species are brand new to science. 

Before the start of the Identidad Madidi expedition, the researchers went through literature pertaining to earlier fish surveys in Madidi and found that 161 species had been recorded for the area. They added a further 172 species during the Identidad Madidi fieldwork, with 21 of them being identified from eggs or larvae alone. They say that this total of 333 species makes the PNANMI Madidi the richest Bolivian protected area for fish. 

Species range in size from the invasive arapaima (Arapaima gigas), a mouth-breathing giant weighing more than 200 kg and measuring over 3 m, to the seasonally abundant killifish (Anablepsoides beniensis) that are found in pools in natural savannas and are just 1.5 cm long. The list also includes the most attractive gamefish from the Amazon, the golden dorado (Salminus brasiliensis), as well as migratory catfish, from the Amazonian goliath catfish (Brachyplatystoma filamentosum) to the tiny chipi chipi pencil catfish (Trichomycterus barbouri) whose massive collective migration is a local phenomenon. 

Another killifish (Orestias sp.) is found in some of the highest Andean lakes at 4,300 m in Madidi, while in the stagnant ponds of the wonderful Amazon, electric knife fish (Gymnotus carapo) and swamp eels (Synbranchus madeirae) occur. In the fast-flowing streams of the Amazon headwaters, several different species of naked catfish (Astroblepus spp.) are found, including some that are likely to be new species for science.

The 35 possible new species include candidates from the genera Knodus, Microgenys, Moenkhausia, Characidium, Apareiodon, Brachyhypopomus, Ernstichthys (genus reported for the first time in Bolivia), Astroblepus and Trichomycterus (including one species recently described and named in honor of a pioneer French ichthyologist in Bolivia). In addition, a three-barbled catfish (Cetopsorhamdia), a striking pike cichlid (Crenicichla) and a charming bumblebee catfish (Microglanis) are also among the brand new species. 

The researchers recorded four alien species (1.2 percent) as being present in the PNANMI Madidi, and report that they also identified fish species from four genera that have never been listed in Bolivia before. The largest number of species are found in the order Characiformes (139 species; 41.7 percent), followed by Siluriformes (137 species; 41.1 percent), and Cichliformes (19 species; 5.7 percent), which together represent 88.6 percent of species richness. 

“With an extension of 18,957.5 square kilometers (7,319 square miles), Madidi covers 1.3 percent of the Madeira River basin, but conserves 25 percent of the known species in the basin. Madidi also represents only 1.8 percent of the Bolivian territory, but it conserves almost 40 percent of the ichthyofauna recorded in Bolivia,” said lead author Guido Miranda. “This study has more than doubled our knowledge about fish diversity in this incredible protected area, but with several sub-basins yet to sample in the park, this is only the beginning.”

Madidi is one of the most important protected areas in Bolivia and the world because of its extraordinary biological richness, which is expressed in its diversity of ecosystems and flora and fauna species. It contains 13 major vegetation types, including the best example of pristine savannas and the largest and best-preserved montane forests in Bolivia.

“Due to its great diversity of habitats, mostly as a result of the altitudinal gradient from 184 meters (Heath River) to 6,044 meters (Chaupi Orko Peak), Madidi is considered the most biodiverse protected area on the planet. The Identidad Madidi initiative aimed to firmly establish this record-breaking status for the park, whilst communicating the importance of Madidi to the Bolivian people,” said study co-author Dr. Rob Wallace. “This is the first of several biodiversity summary articles that the Bolivian scientists on the expedition are systematizing to share the results of our efforts with Bolivia and the world.”

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By Alison Bosman, Earth.com Staff Writer

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