As a bioacoustics intern with the Marine Sensory and Neurobiology Lab at USCB, my primary responsibility was to analyze data as part of an ongoing risk assessment project. The lab has been collecting passive acoustic data from the May River in Bluffton, South Carolina as part of an effort to build a soundscape of the typically turbid local waters. Acoustic recorders (i.e., DSG-Oceans) were deployed at four stations (i.e., 4M, 9M, 14M, and 37M) from the source to the mouth of the May River from February to November 2013. Previous work done on the relationship between the boat engine noise in the area and fish acoustic communication determined that engine noise increased during summer months and could potentially have a negative effect (i.e., interruption of chorusing) on fish species that communicate acoustically, such as silver perch, black drum, oyster toadfish, spotted seatrout, and red drum. To further investigate the risk of boat noise on fish chorusing, I organized all the files from 2013 that included just boat noise by itself into three categories (i.e., Low Frequency, Variable Broadband, and Burst Broadband). By comparing clipped files of boat noise to the ambient sound in either the same file or a temporally and spatially related file, I was able to calculate a received sound pressure level (SPL) of the boat alone as well as a difference in power spectral density (PSD) between the ambient sound and the boat noise. Comparing the PSDs of these three categories to known PSDs of fish in the area allowed me to assess the risk of overlap in frequency from the different boat types. I also evaluated the duration of boat noise vs. duration of chorusing over the entire season of each species to evaluate impacts of the overlap in time. As expected, there was some PSD frequency overlap with the boats and the fish, especially with black drum. In each boat instance, the SPL of the environment was raised because of the boat noise. As far as duration of boat noise during chorusing times, the most impacted species was red drum because of their shorter spawning season starting earlier in the evening, as well as the close vicinity of the aggregation to the ICW.
Smott, Somers, "Risk assessment of boat noise on fish acoustic communication in the May River, South Carolina." (2016). Internship Reports (Restricted). 3.