Traffic noise blocks fish sex

David Schultz

Traffic noise blocks fish sex

For male blacktail shiners, springtime in the tributaries of the Chattahoochee River means two things: sex and a sore throat. To attract a mate, the fish, a common type of minnow, emits bursts of sounds known as growls that are similar to a cat’s purr. To protect its nest of eggs after mating, it makes popping sounds known as knocks to ward off other males. The streams where blacktail shiners (Cyprinella venusta, pictured) spawn are noisy, with water flowing over and under rocks, creating riffles, shoals, and small waterfalls that could make it harder for the fish to hear each other. Now, humanmade noise, such as from cars and boats, may be masking the animal’s acoustic signals even further, researchers report in Biological Conservation. The study details how the scientists dropped hydrophones in streams, first to record the fish’s natural soundscape in mating areas and then to capture the reverberating sound created by semi-trailer trucks crossing over nearby bridges. In particular, they discovered that, similar to other fish, blacktail shiners have evolved the ability to pitch their mating sounds so as to exploit a “quiet window” in the natural noise spectrum. Road traffic noise, they found, overlapped with that window in a way no natural sounds did and could potentially drown out the fish’s growls up to 12 kilometers from the bridge. Previous research has shown that the minnows may yell to make themselves heard in noisy conditions, but the extent to which the elevated sounds impact their overall reproductive success remains unknown.

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