a1 University of British Columbia, Department of Oceanography, Vancouver, British Columbia, Canada.
The study describes the seasonal density and age structure for splashpool metapopulations of Tigriopus californicus (Copepoda: Harpacticoida). Natural populations were highly variable, ranging from 217 ± 401·7 ind 1−1 in winter (mean ± SE) to 835 ± 1750·6 ind 1−1 in summer, with some populations approaching 20,000 ind 1−1 in all seasons except winter. Male-to-female ratio ranged from 1·36 in spring and summer to 1·84 in autumn, and reproduction was observed throughout the year. Nauplii abundance averaged 28 + 7·4 ind 11, a value much lower than expected for in situ copepod populations and possibly due to behavioural processes such as cannibalism and inhibition of egg deposition. The densest assemblages of splashpool microcrustacea were almost entirely T. californicus, principally mature adults and including clasped male-female pairs and ovigerous females. A simple population growth model is presented, along with parameters for calculating the instantaneous rate of increase, birth, and death in the absence of disturbance.