Golden Mussel's 1,000-km Jump Upstream Raises Alarm for Brazil's Dams

A surprising jump upstream

Researchers from the Universidade Estadual de Montes Claros (Unimontes) confirmed the presence of the golden mussel, Limnoperna fortunei, in the municipalities of São Francisco and São Romão, in northern Minas Gerais. The team, led by professors Magno Augusto Zazá Borges and Maurício Lopes de Faria, collected 113 specimens during five expeditions carried out between July 2024 and April 2025, according to local outlet Webterra.

The finding was formally published on 9 September 2026 in the scientific journal Check List (volume 22, issue 5), with Magno Borges and Marcela Fonseca listed as lead authors among eleven contributors. The research received support from the Public Prosecutor's Office of Minas Gerais, according to the journal's publisher, Pensoft.

Researchers sampled 16 stations across four municipalities along the river, Webterra reported. The mussel was found in every station surveyed in the São Francisco municipality and in one station in São Romão, but it was absent from stations in Ibiaí, Pirapora and the Três Marias reservoir. Because of that gap, the team hypothesizes that the species was carried upstream by small boats rather than spreading naturally along the current — a possibility the researchers describe as not yet definitively proven, according to Webterra.

Three decades of invasion

Limnoperna fortunei is native to China's Pearl River basin. According to CNN Brasil, the species reached South America in 1991, arriving in the La Plata River estuary in Argentina inside the ballast water of cargo ships. It entered Brazilian waters in the late 1990s through the Paraná-Paraguay waterway and has since spread through reservoirs and rivers across the South, Southeast, Center-West and parts of the Northeast over roughly three decades. No confirmed cases have been recorded in the North region.

Before the new discovery, the northernmost confirmed record on the São Francisco River was at the Sobradinho Reservoir, on the border between the states of Bahia and Pernambuco, documented in 2016-2017, CNN Brasil and Webterra reported. The new finding in northern Minas Gerais sits about 1,000 kilometers upstream of that previous record.

Why hydroelectric plants are vulnerable

The golden mussel forms dense colonies on hard surfaces, which can obstruct the pipelines and cooling systems that hydroelectric plants rely on. CNN Brasil reported that Brazil's electricity sector spends approximately US$9.97 million a year on prevention and control measures tied to this biofouling. Beyond power generation, the outlet noted that the invasion also affects drinking-water intake systems, fish farming, commercial fishing, navigation and native aquatic ecosystems.

According to CNN Brasil, full eradication of the species is considered unlikely once it establishes itself in a water body. Current countermeasures include physical methods such as scraping, high-pressure jetting, filtration, ultrasound and UV radiation; chemical approaches such as anti-fouling coatings, sodium hydroxide and chlorinated compounds; and ongoing research into biological controls, including microbial agents. Prevention efforts focus on disinfecting vessels with bleach and requiring health certificates for fish shipments moved between river basins.

What happens next

Webterra reported that the Três Marias reservoir, located upstream of the newly confirmed infestation site on the São Francisco River, remains free of the golden mussel. Researchers describe this as a window of opportunity for monitoring and preventive measures before the species potentially spreads further into the river's middle and upper stretches.