Feeding by Chaetognatha: The Relation of Prey Size to Predator Size in Several Species

Abstract

The mean size of prey items, measured as body width (H), 1s related to chaetognath predator head width (P) of several chaetognath species as a power curve: H = a Pb with 'a'varying between 0.33 and 0.86 and 'b'behveen 0.27 and 0.82. This is the expected general form of the relationship when predators and prey have different allometric exponents. There are a number of artefacts of laboratory and statistical analyses which can affect the magnitudes of these coefficients. In general, however, real differences in the prey/predator size relationship seem to exist between species, and within species in different areas. Because chaetognaths are probably one of the main sources of predation pressure on the copepod community, both the general form of their prey-size selection and differences in this function between species should have considerable influence on the size structures of lower trophic levels.