2016 JISAO Internship Program
How variation in acoustic instramentation alters perceptions of pelagic bilogy
My name is Michael Espriella, and I am pursuing a degree in Environmental Studies at the University of Southern California. This summer I was fortunate enough to be accepted into the JISAO summer internship program.
Throughout the summer I worked with Dr. John Horne in the University of Washington School of Aquatic and Fishery Sciences. More specifically, I was part of the Fisheries Acoustics Lab working on a project that focused primarily on how differences in acoustic instrumentation alter perceptions of the water column. Data from acoustic sampling is often used to make policy decisions, therefore understanding how instrumentation affects decision making is essential.
I started my internship by traveling to Friday Harbor on San Juan Island where we would board the RV Centennial to collect data around Friday Harbor as well as calibrate transducers. In Friday Harbor we used the Kongsberg M3 (500 kHz) and the Simrad EK60 (38 kHz and 120 kHz), which would become the main subjects of my study.
After Friday Harbor, we traveled to Newport, Oregon on the RV Centennial to run transects on two regions around marine renewable energy test sites. We also trawled to contextualize the biomass that appeared on the acoustic recordings. Transects were run both day and night to account for the variability in biomass and species distribution at different times of day.
Upon return to Seattle, I began to process data collected to determine differences between the M3 and the EK60. I used a software called Echoview to begin by adjusting surface and bottom lines as well as removing background noise and detecting schools and single targets. Three-dimensional models were created to examine qualitative differences. Following this, a grid was established for both the M3 and EK60 data to begin quantitative assessments. Variables measuring density, location, dispersion, and aggregation of biomass were all considered. Autocorrelations were also calculated for the two data sets.
I found that the EK60 echosounder results suggest that there are more aggregations in the water column when compared to a more uniform distribution from the M3 multibeam sonar. The relationship between the two was not linear as a result of differences in frequency, beam angle, and data processing. The autocorrelations also suggested that echosounder samples are independent at twice the distance of the multibeam sonar.
The JISAO internship experience was not limited to my individual project. I was immersed into numerous fields of study thanks to the seminars and interactions with fellow interns. Having direct contact with the members of the FAR Lab was also extremely beneficial, especially with the graduate students as I begin to think about potential graduate programs myself. The program has provided me with a strong foundation to continue my pursuits in marine science research and I am very grateful for the opportunity given to me by JISAO.
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