Highway bridge noise disturbs fish’s hearing

WEST PALM BEACH, Fla. — Loud recordings of traffic rumbling over highway bridges can cause rock-concert hearing shifts in lab fish that normally live in Alabama streams. After two hours of broadcast traffic noise in the lab, small silvery fish called blacktail shiners (Cyprinella venusta) could no longer detect some important sounds as easily as fish not exposed to the highway din. Jenna Crovo of Auburn University in Alabama reported the findings January 5 at the annual meeting of the Society for Integrative and Comparative Biology.

Shiners not subjected to recordings could hear the upper peak of their species’ courtship growl when tones were played at about 80 decibels. Fish subjected to traffic broadcasts didn’t hear those tones until researchers played them about 10 decibels louder. Whether the threshold shift is permanent or the fish’s hearing returns to normal — as often happens in human concertgoers who experience similar shifts — remains to be seen.