Principal component calibration models in the acoustic evaluation of zooplankton size spectra

The theoretical basis of application of PCR (principal components regression) methods to the estimation of zooplankton size spectra by multifrequency acoustical methods is presented. Preliminary performance studies on simulated data are preformed to test the capacities of this technique as a function of the acoustic signal‐to‐noise ratio (SNR) and the type of acoustic scattering model. The results are compared with those obtained with a non‐negative least squares (NNLS) algorithm, and finally, an application to a real data matrix is shown. The main advantage over the NNLS method is that it avoids the knowledge of the scattering responses for each class of particles. The results obtained on simulated data indicate that PCR calibration models are good alternatives for the estimation of size spectra, in the range tested. For all the conditions analyzed, the error estimators and correlation coefficients show a better fit than NNLS models. The real data matrix tested is particularly complex, avoiding the use o...