Dr. Dezhang Chu was awarded the NOAA Bronze Medal for creating EchoPro, software that analyzes raw acoustic data for fisheries biomass estimates. Dr. Chu is a physical scientist with the Acoustics Team of the Fishery Resource Analysis and Monitoring Division.
Center scientists will use the EchoPro software to rapidly and efficiently analyze the tremendous amounts of data collected from the joint U.S. - Canada integrated acoustic and trawl survey of Pacific hake. The survey, a collaboration between the United States and Canada, uses acoustic echosounders and trawls to estimate the population of Pacific hake off the West Coast of North America. Pacific hake, also known as Pacific whiting, is one of the largest fisheries on the West Coast, with landings valued at over $27 million in 2010.
How an acoustic survey works
To conduct an acoustic survey, sound waves are sent down from a ship using an underwater acoustic transducer, a piece of equipment mounted on a retractable centerboard on the bottom of the vessel that takes energy and converts it into sound. When the sound hits an object that has different acoustic properties than the surrounding seawater, such as a school of Pacific hake, the sound bounces back. The resulting information, called backscatter or echo, is recorded by a computer-controlled data acquisition system. Scientists then analyze this data to estimate the biomass of Pacific hake.
Analyzing the data
The recorded backscatter—along with biological information from trawls used to verify the results—adds up to an immense amount of data each year. Until 2009, it took several months to initially analyze the data using an Oracle database. In addition, much more processing time and effort was needed to adequately address requests by the Pacific Hake Stock Assessment Review Panel.
Dr. Chu wanted to find a way to analyze the data more quickly and efficiently, and in 2009, he began developing the EchoPro software package in MATLAB, a programming environment developed by MathWorks. Built on a Graphical User Interface (GUI) platform, EchoPro allows the user to analyze both current survey data and historical data that reaches back to 1995. Processing with EchoPro is much faster than using the previous Oracle-based system, along with having more flexibility to produce different products including simultaneous biomass and variance estimates; biomass structured by sex, age, and length; and biomass tied to geographical region or even individual survey transect. These products are presented in forms that range from 3D charts to histograms.
Incorporating kriging to provide more robust results
To make the results even more robust and to allow a more flexible survey transect design, Dr. Chu incorporated a geostatistics technique, known as kriging, into EchoPro. Kriging is a geostastical estimation technique that was developed for the mining industry in the 1960s, and is the best linear unbiased estimator (BLUE). What this means is that unbiased biomass estimates can be made for unsurveyed areas by utilizing information about nearby sample locations. To complete these estimates, EchoPro integrates the program EasyKrig 3.0, software developed by Dr. Chu while he was a scientist at Woods Hole Oceanographic Institution.
What happens next?
After a two-year trial period, the Pacific Whiting Treaty Scientific Review Group, part of the treaty organization that manages the species, approved the use of Chu’s EchoPro software to complete the biomass estimate and other analyses for future hake acoustic and trawl surveys, starting with the data collected in summer 2012.