Use of passive acoustic monitoring to characterize fish spawning behavior and habitat use within a complex mosaic of estuarine habitats

Structurally complex estuarine habitats, such as seagrass beds, salt marshes, and oyster reefs, are used by fish for foraging, avoiding predators, and spawning. Here, we used passive acoustics to characterize spatiotemporal patterns in the soundscape of an estuarine reserve that contained a mosaic of habitat types, and focused on relating characteristics of the soundscape [e.g., low-frequency (150–1500 Hz) sound pressure levels (SPLs), amount of fish chorusing] to patterns in the seascape (percent cover of estuarine habitats surrounding the recording sites). Over a 3-mo period, 2-min duration underwater sound recordings were made every 20 min at eight sites within Middle Marsh in Back Sound, North Carolina, USA. While habitat composition was not related to spatial patterns in low-frequency SPLs, there was a positive and statistically significant relationship between the percent recordings with fish chorusing, and percent cover of seagrass for silver perch [Bairdiella chrysoura (Lacepede, 1802)], spotted seatrout [Cynoscion nebulosus (Cuvier, 1830)], and other fish, irrespective of spatial scale (10 vs 25 m). Moreover, silver perch and spotted seatrout, soniferous species that share similar spawning locations, exhibited temporal partitioning in the soundscape with seatrout calls occurring just before sunset and peaking several hours after sunset, and declining sharply as perch chorusing increased after sunset with a peak at midnight. Overall, local habitat composition and the soundscape at these sites were not highly correlated; where major sound producing fish species are transient, other seascape characteristics, such as proximity to channels, likely have a larger influence on the resulting soundscape.