Could bubbles and strobe lights stop pest fish swimming where they’re not wanted?
A team of NIWA freshwater scientists is investigating the effectiveness of an acoustic bubble-screen coupled with strobe lights in preventing pest species such as koi carp moving into critical habitats.
Pest fish species are a leading threat to biodiversity globally, as well as being economically costly and causing ecological damage.
The management of pest fish is currently limited to preventing their spread, focusing largely on physical removal or poison (piscides), but these methods are not effective in all situations, or cost effective.
The Bio-Acoustic Fish Fence (BAFF), a unique innovation in pest fish management, could be a new solution. This innovative system uses sound and bubbles to create a disruptive force against unwanted fish, offering a promising alternative to traditional pest control methods such as physical removal and toxic treatments.
The BAFF was developed by Fish Guidance Systems in the UK and NIWA researchers have been testing it on koi/amur carp, perch and shortfin eels as a selective barrier that prevents undesirable species from moving into critical habitats but does not prevent the movement of desirable native species in and out of the area.
“The system works by producing a combination of underwater sound bursts that resonate a bubble screen, which disrupts some fishes’ behaviour,” said NIWA Principal Scientist Freshwater Fish, Dr Cindy Baker.
“The bubbles, created by compressed air, form a barrier, while speakers emit sound waves between 20 to 2000 Hz—frequencies that are uncomfortable for some fish,” she said. “When paired with strobe lights, the BAFF becomes even more effective in deterring some pest fish species, in particular koi carp.”
In a recent study overseas, the BAFF successfully blocked up to 97% of bighead carp from passing through the system. Additional trials showed similar success in repelling a variety of carp species, including common carp and silver carp.
“What sets this technology apart is its ability to achieve this high level of deterrence without harming native species, such as shortfin eels, which have also been tested for their reaction to the system,” says Dr Baker.
“The implications for pest fish management are positive. By effectively blocking the movement of invasive species like koi/amur carp, the BAFF could prevent them from reaching their spawning grounds, disrupting their reproductive cycle, and limiting their population growth.”
She says this could also help protect native freshwater species and prevent ecological damage caused by these pests, which increase turbidity in lakes and often outcompete local species for food and habitat.
NIWA’s research on the BAFF is ongoing, with continued testing focusing on the system’s impact on both migrating and resident feeding eels. Researchers are also investigating how suspended sediment in turbid waters might affect its performance. The results so far suggest that the system’s level of deterrence may depend on water clarity, but with further refinement, it could become an invaluable tool in the global fight against invasive pest species.
This NIWA Freshwater Biosecurity programme research is funded by the MBIE Strategic Science Investment Fund.
