2 freshwater fishes endemic to Madagascar have disappeared

The reasons for this are: building dams on rivers to drain wetlands, withdrawing too much water for irrigation, releasing too much untreated waste, unsustainable fishing, introduction of invasive species and non-native species, and last but not least: the worsening effects of climate change.

According to this report, 80 species of freshwater fish are already extinct in the world, including two in Madagascar: Ptychochromis onilahy (Kotro) and Pantanodon madagascariensis, listed in the IUCN Red List in 2016.

The Ptychochromis onilahy was an endemic fish of southwest Madagascar, it lived in the Onilahy river, influential of the protected area of Amoron'i Onilahy. Despite several recent visits to the region, this species has not been recorded since 1962, in fact it is at this date that the only five known specimens were collected.  They represent the only known material collected in the Onilahy River. It is classified as extinct by the IUCN. It should be noted that its initial classification was done before its official description. It was therefore listed under the temporary name of Ptychochromis sp. This species can reach a length of 8.6 centimeters.  The causes of its disappearance are the destruction of their habitats due to deforestation, competition with other introduced fish species including Tilapias and overfishing. Indeed, more resistant and resilient fish such as the Tilapia invade the living areas of the Ptychorochromis o., which has a negative impact on their development and has undoubtedly contributed to their extinction.

The various lakes, swamps, the Onilahy River, the forests along the river, and the swamps in the Amoron'i Onilahy protected area form the Onilahy Ramsar site. It is home to 27 species of mammals; 56 species of reptiles, 79 species of birds including waterfowl; and the fish species Allenbatrachus meridionalis, also listed in the IUCN Red List.  These wetlands have always been threatened by deforestation (for agriculture and charcoal production). 

As for the Pantanodon madagascariensis, it was an endemic fish of eastern Madagascar, of the rivers of the eastern slopes between Mahavelona and Fenoarivo and in the district of Fénérive Est. The reasons for its extinction are the destruction of wetlands, converted into rice paddies, and competition with other species in the same habitat including Gambusia, which is an introduced species.

As freshwater and the species within it become extinct, there is a dysfunction of freshwater ecosystems around the world. We know that freshwater is the source of drinking water and irrigates our agricultural fields. Healthy freshwater ecosystems are also essential in the fight against climate change through their carbon storage functions.  In terms of production, Africa accounted for 25% of the world's recorded freshwater fish production, or 3 million tons (FAO 2020).

The solution recommended in "The World's Forgotten Fish" is to implement an emergency recovery plan for freshwater biodiversity, developed by scientists and freshwater experts around the world. This approach should include the following pillars: allowing rivers to flow more naturally, improving freshwater quality, protecting and restoring critical habitats, ending overfishing and unsustainable practices, preventing and controlling invasions of non-native species, and protecting free-flowing rivers and removing obsolete dams.