Estimation techniques used in studies of copepod population dynamics - A review of underlying assumptions

The literature on zooplankton population dynamics provides more estimation techniques than reliable estimates of population parameters. In this review we show how different techniques relate to each other in terms of underlying models and assumptions. There are two main routes to parameter estimates. The vertical approaches utilize the stage-structure of samples taken at the same point in time. They require assumptions about the constancy in the parameters, but relax assumptions concerning advective influence. The horizontal approaches utilize information provided by the stage structure within samples, as well as information on temporal changes in abundance. They relax assumptions about the constancy of parameters, but advective influences may be introduced. Of the horizontal methods, variants of what are commonly termed cohort methods have been widely used. These provide mathematical simplicity, but are based on more restrictive assumptions than methods fitting predescribed models (delay differential, partial differential equation, and matrix models of population dynamics). Because the quality of estimates, such as of mortality rates, depends upon the quality of the data, some sampling considerations in regard to advection and biases in estimating stage composition are discussed. It is important to reduce the number of parameters to be estimated from census data, thus we review some techniques for independent measurement of stage durations and birth rates. Finally, we provide some general recommendations for future studies.