Dependence of feeding rates on body mass when food density is limiting to growth

Bioenergetics models are commonly used to predict effects of changes in metabolic rates and food availability on growth. However, food intake rate generally is assumed to vary as Wd, where d = 2/3, an assumption based on observations from feeding trials in laboratory studies. Further, the von Bertalanffy growth function (VBGF) is specifically integrated using this assumption. We argue that when considered from an ecological perspective, d is highly uncertain, dependent on how swimming speed, reactive distance, and prey biomass varies ontogenetically with the growth of a predator. Incorrectly specifying d leads to incorrect predictions of consumption and metabolism, especially at younger ages that are typically under-sampled. Three alternate means of detecting departures from d = 2/3 are provided, the most promising of which involves fixing initial length of the generalized VBGF to the length at endogenous feeding and directly calculating von Bertalanffy parameters (L_∞,K,t_0). Using this approach it may be possible to more accurately estimate consumption and metabolism and to characterize lifetime growth.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author