The effects of interaction of rate of food supply and population density on the bioenergetics of the opportunistic polychaete, Capitella capitata (type 1) 1

Weight‐specific growth rates, population production, and trophic transfer efficiency (worm production/food supply) of different size classes of the polychaete Capitella capitata (type 1) were measured in the laboratory at 20°C under varying conditions of population density and rate of food supply (ration). A hyperbolic tangent function was fitted to the response of individual growth to unit nitrogen of food supply available per unit nitrogen biomass of worm ( R : B ̄). Maintenance ration, where growth = 0%, occurred at an R : B ̄ = 0.08; i.e. a 0.08 g N daily ration of food was needed to maintain 1 g N biomass of C. capitata. Maximum daily individual growth rates of 21, 19, and 15% were predicted for small, medium, and large worms. The individual growth data were combined with long term‐population data collected at three food rations (50, 100, and 150 mg N m −2 d −1 ) to estimate long term population production. Changes in population density and the presence of meiofauna reduce the actual worm production for a given rate of food supply. Population production and trophic transfer efficiency changed dramatically as a function of rate of food supply, worm size, and biomass.