Tailings dams affect diversity of upstream fish species – study

A recent study by Brazilian researchers found that streams flowing into tailings storage dams (TSDs) had fewer catfish species, including fewer armoured catfish and fewer small predaceous catfish common to steep-slope streams.

The paper, which was published in the journal Water Biology and Security, explains that there are at least three aspects that need to be considered when analyzing the impact of tailings facilities on upstream fish assemblages: life-cycle disruption, species intolerance or tolerance to lentic or still freshwater conditions, and non-native species.

The research was conducted in the Rio Doce basin in southeastern Brazil. To collect fish, the team used standard methods in 24 sites, half draining to TSDs (dammed) and half free from this impact (not dammed).

To identify differences between treatments, they used permutational multivariate analysis of variance or PERMANOVA. This allowed them to test both environmental variables and the assemblages of fish in each waterbody, and evaluate the biological metrics that most influenced assemblage composition change.

“Despite natural forest cover in most of the catchment area, we observed a decrease in these species that rely on stream continuity and high-quality water,” Gilberto Salvador, lead author of the study, said in a media statement. “In comparison, two other widely tolerant species had increased in numbers along with one species commonly found in TSDs.”

The team attributed these results to re-colonization barriers created by tailings storage dams, as well as colonization sources for tolerant species.

“Our findings underscore the need to consider downstream alterations caused by TSDs when assessing reference conditions for biomonitoring and bioassessment studies,” Salvador said.