| Abstrakt: |
In weekly exploited populations of the harpacticoid copepod Tisbe holothuriae Humes, the dynamics of population development and the effect of the rate of water renewal were studied under conditions of surplus food supply, constant temperature (22° C) and salinity (30 ‰). At exploitation rates of 10, 30, 50, 70 or 90% per week, the populations maintained stable mean populations sizes. None of the populations established stationary equilibria. Reduced rates of water renewal resulted in a reduction of mean population density, in the course of which the density of adults plus copepodids was diminished to a lesser degree when low, as opposed to high, percentages of specimens were removed. The density of nauplii was distinctly reduced at all exploitation levels. The age structure shifted in favour of the adults and copepodids and was subject to higher variability at moderate exploitation rates and lowered rate of water renewal. To avoid and to remove difficulties inherent to current concepts of population dynamics, the populations were regarded as a component of a feedback control system, and an attempt has been made to describe the observed processes by analogy to technical control systems. According to not yet completed series of experiments, populations undergoing higher exploitation rates seem to compensate more succesfully for perturbations of their environment, than populations exploited at lower rates. [ABSTRACT FROM AUTHOR] |
