Bioenergetic model and specific growth rates of jellyfish Aurelia spp

The common jellyfish Aurelia spp. often appears in large numbers in coastal regions around the world, having a considerable predation impact on zooplankton. To better understand and quantify this phenomenon, several laboratory and field studies have determined growth rates by recording umbrella diameter and/or dry weight versus time. However, there appears to be no model describing such data. Here, we use a bioenergetic model for growth of Aurelia spp. dry mass (W) based on ingested food minus respiration, leading to the weight-specific growth rate μ (1/W) dW/dt = aW^b, where the constant a depends on prey concentration and the exponent is b = -0.2. The model is tested against Aurelia spp. data in several examples, some of which represent well-fed conditions that show fair agreement with the model (b = -0.2 to -0.4), while others depart increasingly from the model (b < -0.4) with increasing W, likely due to suboptimal and fluctuating prey concentrations. Based on the model and available data, it is suggested that for a given size W, the specific growth rate increases linearly with prey concentration up to about 5 to 6 Artemia sp. l^-1, where a maximal growth rate (μ_max) is reached which is not exceeded for higher prey concentrations.