Study points to better sound cues for steering juvenile grass carp

Juvenile grass carp showed clear avoidance of some sounds, but not all, in a newly published Animals study that tested acoustic deterrents in semi-natural outdoor net cages. The researchers compared a 1000 Hz pure tone with three broadband sounds — Alligator sinensis hissing, pile-driving noise, and outboard motor noise — and found the strongest response to alligator hissing, with outboard motor noise also producing stronger avoidance than the pure tone or pile-driving sound. The paper, published May 3, 2026, concludes that both sound type and timing structure can shape negative phonotaxis, or movement away from sound, in juvenile grass carp. (mdpi.com)

Why it matters: For veterinary and aquatic animal health professionals, the study adds field-like behavioral evidence for non-physical fish guidance tools that could reduce entrainment risk around dams, pumps, and other hydraulic structures without relying solely on screens or nets. That matters both for fish welfare and for invasive carp management, especially because USGS and other agencies have been evaluating acoustic deterrents as part of broader containment strategies for invasive carp in North American waterways. Prior work has shown grass carp can detect a broad frequency range, but experts have noted that behavioral testing is what determines whether a sound is actually useful as a deterrent in practice. (usgs.gov)

What to watch: The next question is whether these broadband sounds, or modified versions of them, can hold up in larger open-water and infrastructure settings while limiting unintended effects on non-target fish species. (usgs.gov)