Field test of a low-voltage, portable electric barrier to guide invasive common carp into a mock trap during seasonal migrations

Common carp (Cyprinus carpio Linnaeus, 1758), one of the world’s most invasive fish, is known for their extensive seasonal migrations. Often, adult carp migrate between lakes and marshes (spawning grounds) in early spring in large synchronized events. If these fish could be directed into traps, sustainable carp management schemes could be developed for many lake-marsh systems. In this study, we used a portable low-voltage electric guidance system (EGS) to direct common carp into a mock trap in a relatively large natural stream. The system was tested on 6 occasions: 3 days with EGS off and 3 days with EGS on. Approximately 40 adult carp were used in each test. All were implanted with passive integrated transponders (PIT) and ten in each group also had visual markers. When the EGS was on, PIT data indicated that 74% of the carp were successfully guided into the mock trap, while visual markers indicated that no carp were able to cross through the EGS despite over 300 attempts. When the EGS was off, PIT data indicated that only 18% of carp swam into the mock trap, and visual markers showed that many were able to swim though the EGS (22 out of 29). The electric field generated by the EGS was mild and did not cause fish paralysis. The EGS required little on-site engineering and was deployed in 2 days. This new type of EGS might prove useful for managing invasive fish or for conservation of native species that employ seasonal migrations.