The famous saying goes that if you are forgetful you have a ‘memory of a fish’, but contrary to this idiom, it has been demonstrated through research on invasive carp species that fish have good memories – especially when it comes to learning to avoid stimuli that they see as uncomfortable or harmful.

This behavior is seen in a wide range of fish but more importantly, for research purposes, is shown in the invasive species of bighead, grass, black and silver carp currently affecting the ecosystems of the Mississippi Basin. Fish Guidance is using research done by academics across the US by using a BioAcoustic Fish Fence (BAFF) to control the populations of invasive carp in the Mississippi Basin.

BioAcoustic Fish Fence (BAFF) trial

A BAFF trial is currently being delivered at Barkley Lock on the Cumberland River in Kentucky – a tributary of the Mississippi River and this ‘learn to avoid’ behavior is contributing to the high efficiency of the system.

BAFF systems are used to control the spread of invasive species and ‘combine repellent sound signals with an air bubble curtain. Sound Projectors are mounted on a chassis in sections, along with bubble pipes, and these sections are lowered to the river bed.’

Once connected, they form a barrier of sound and air that can be used to guide the fish, and yet still allow vessels to freely pass by.’

Research on ‘learning to avoid’

Research done on the subject, entitled ‘Response of bighead carp to a bioacoustic

behavioural fish guidance system’ by R.M. Taylor, J.H Chick  and M.A. Pegg at the Illinois River Biological Station Illinois Natural History Survey, Havana, IL, USA, showed that in addition to the initial, expected deterring of the fish from crossing a barrier – there were fewer subsequent attempts made over the following days, implying that bighead carp learned to avoid the barrier. The report also states:

“Thirty-three bighead carp made a total of 284 attempts to cross the functional SPA driven BAFF system during the three trials. Of those observed attempts, 95% were repelled. A marked decrease in the number of attempts, but a consistently high number of repels in relation to those attempts on the second and  third day, was also observed.  This decrease in attempts suggests that the bighead carp learned to avoid the barrier”.

These observations for silver and bighead carp, are consistent with other research, including that carried out more recently by Dr Peter Sorensen’s research group based at the University of Minnesota, where Dr Clark Dennis, Dr Dan Zielinski and Dr Peter Sorensen (2019) commented “Also notable was our finding that the proprietary sound [of the BAFF] kept a greater number of common carp and bighead carp away from the deterrent…..this proprietary sound decreased the number of carps observed near the speaker system”.
The fight against invasive carp is a difficult one, but using robust and proven techniques such as BAFF systems can help in the controlling and reduction of invasive species. To find out more visit our invasive carp minisite here.