Comparison of estimates of the predatory impact of ctenophores by two independent techniques

The common methods for estimating food consumption in the environment involve either (1) performing experiments in the laboratory and relating food concentrations used to those in the environment, or (2) analyzing gut contents of animals directly from the environment and estimating food consumption by some knowledge of gut residence time. Both techniques involved compromises and assumptions. The greater precision and speed of the laboratory approach is counterbalanced by the impossibility of duplicating the natural feeding milieu. We compared predation rates of the ctenophores from gut content analysis of ctenophores in 1 300 m³ enclosures, with the estimates of expected predatory effects based on controlled laboratory experiments, over a wide range of ctenophore size and food concentration. Despite some larger discrepancies, the two methods often yielded results within a factor of two of each other.