Seven years (1970-1976) of density data on three harpacticoid copepods were analysed by Maximum Entropy spectral Analysis. The spectra are very different, indicating population regulation is also different. Tachidius discipes is regulated by external seasonal factors, mainly the annual light cycle, and has a very simple spectrum. Canuella perplexa has much longer cycles in its spectrum and can be treated as a single species problem with logistic dynamics Paronychocamptus nanus has also a complex spectrum that can partly be explained by competitive interactions
