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# One invasive fish can suppress another—and leave a native remnant in the middle
- URL: https://intelligence.wildlandseco.com/2026-09-25-invasive-fish-interactions-breede-river/
- Published: 2026-09-25T11:24:39.000Z
- Updated: 2026-09-25T11:24:39.000Z
- Description: In South Africa’s Breede River, flow barriers, turbidity and abundant sharptooth catfish appear to damp black-bass predation enough for an endangered whitefish to persist at extremely low frequency.
- Author: Benjamin Worlund
- Tags: invasive fish, Breede River, freshwater community, flow barriers, invasive species, Freshwater, fish, Community ecology, Connectivity, #ecological-intelligence, #brief-2026-09-25, #priority-read, #peer-reviewed, #geo-africa

Evidence

Peer-reviewed

Geography

Breede River, Western Cape, South Africa

System

River fish community

## WHAT THE EVIDENCE SAYS

A river survey recorded 2,546 fish representing 17 species, seven of them introduced. Sharptooth catfish frequency was negatively associated with fish diversity, while invasive black bass showed the opposite broad association; flow barriers, high catfish abundance and turbidity appeared to suppress visually hunting bass enough for endangered Berg-Breede whitefish to persist at very low frequency.

## WHY IT MATTERS / OUR READ

In invaded systems, management can face interacting pressures rather than one clean native-versus-invasive axis. Removing one stressor can change the effect of another, which makes food-web and barrier context relevant to control decisions.

## CAVEATS / UNCERTAINTY

The whitefish remnant is persistence, not recovery. The evidence is observational and site-specific, and antagonism among invasive fishes is not an argument to retain invasive species or barriers; intervention effects would need direct testing.

## SOURCE

Biological Invasions  
[View original evidence ↗](https://link.springer.com/article/10.1007/s10530-026-03935-y?ref=intelligence.wildlandseco.com)

From the Morning Brief · 2026-09-25

[Read the full Morning Brief →](https://intelligence.wildlandseco.com/morning-brief-2026-09-25/)