A Fourier Transform Approach for Automatic Detection of Oysters’ Spawning

Various studies have been developed to monitor the gaping behavior of bivalves (oysters) in response to environmental factors. This work aims to fully automate oyster spawning detection in real-time by building on previous efforts. The sensor system developed at Jackson State University, Mississippi, employs the Hall effect phenomenon to accurately measure the gaping of bivalves accurately. The system uses a Hall effect sensor and a small magnet glued outside the bivalve shells. The Hall effect sensor reports the magnet distance, and hence the gape at a rate of 10 Hz, which the user may change. The data generated is stored on an SD card and supplied to a microcontroller for transmission to our file server on the Internet. The collected time series data is transformed to the frequency domain in 10-minute chunks using the fast Fourier transform (FFT) algorithm. When the data is analyzed in the frequency domain, the spectral power in the frequency range of 0.3 Hz to 1.3 Hz spikes several orders of magnitude when spawning occurs. It is then concluded that using a threshold of 0.1 dB in the frequency range of 0.3 Hz to 1.3 Hz, and spawning could be predicted 100% of the time.