Energetic costs and benefits of cyclic habitat switching: a bioenergetics model analysis of diel vertical migration in coregonids

Recent studies on diel vertical migration (DVM) of two coregonid species ( Coregonus spp.) in Lake Stechlin (Germany) have suggested that the nocturnal distribution of fish is linked with metabolic benefits. We used a spatially explicit bioenergetics-based foraging model to test whether energetic constraints contribute to explain DVM of both species. The newly parameterized model was compared with independent data from Lake Stechlin that covered a 9 month period. Predicted growth rates matched observed growth rates of each fish species reasonably well. The simulation of different migration scenarios showed that even slight changes in night-time depths modified growth rates, primarily owing to temperature-dependent respiration. Fish that performed DVM grew faster than nonmigratory fish that occupied deep hypolimnetic water over a diel cycle. However, the most energy-efficient strategy simulated had fish remaining within the metalimnion. Here, energetic benefits (foraging) clearly outweighed higher energetic costs (respiration) in the warmer waters. Although DVM can be energetically beneficial, it is not the most efficient strategy performed by coregonids in Lake Stechlin. We suggest that multiple factors, rather than bioenergetics efficiency alone, are the evolutionary basis for DVM of many freshwater fish species.