Generalized linear models were used to assess the influence of diel vertical migration (DVM) on Continuous Plankton Recorder data for adult (stages V and VI) Calanus finmarchicus. To simplify interpretation, the data were first divided into individual months and modelled using a Generalized Linear Model incorporating factors for long-term trend and daylight. The fitted models reveal that, at certain times of the year and particularly during the spring and autumn, the chances of catching a stage V or VI C. finmarchicus at 7 m depth are greater in darkness than during daylight. The magnitude of DVM was shown to be generally statistically independent of long-term trend, which is a conclusion that fails to support other published results produced from the same data.
