Impact of environmental factors on calling behavior in midshipman fish across ocean basins

ABSTRACT Chorusing is widespread across the animal kingdom. Animal calling behavior is often driven by phenological and environmental factors such as seasonality, lunar period, and temperature. Now, in the Anthropocene, factors such as increased anthropogenic noise levels are also affecting calling behavior. Many fish call in choruses to attract mates, but the dynamics that drive fish calling behavior have rarely been studied in the field. We investigated how seasonality, lunar period, ambient noise, and temperature influenced the calling behavior of two species of toadfish, the plainfin midshipman ( Porichthys notatus ) and putatively, the Atlantic midshipman ( Porichthys plectrodon ). Acoustic recordings from a two-year period in twelve different locations, spanning two ocean basins showed that midshipman chorus presence was driven by seasonality and lunar period. Furthermore, chorus frequency increased with increasing temperature. Chorus levels were strongly influenced by seasonality and increased somewhat with increasing noise levels. Taken together, these results indicate that midshipman calling behavior was strongly influenced by interacting environmental conditions. Understanding the various impacts of each driver will facilitate predictions of changes in midshipman calling due to future changes in environmental conditions.