Life history and productivity of Pectinaria koreni Malmgren (polychaeta)

Growth, survivorship, reproduction and productivity of a Pectinaria (Lagis) koreni population was studied in Colwyn Bay, from July 1975 to August 1976. The cephalic disc diameter of the worms was chosen as an index of size, after the relations between linear and weight measurements of the body were established. Settlement of Pectinaria was estimated to have occured at the beginning of June, and the whole population had disappeared by April. Growth was initially fast but it ceased completely during the winter, probably due to low temperatures and disturbance by storms. Bundles of gametes first appeared in the coelomic fluid in November, but maturation was not completed before May. Mature ova, 60–65 μ in diameter, were released individually: sperms, a few microns in diameter, were released in bundles. The highest standing crop, 47·5 g m^?2 was present in September and the total production of the cohort during its lifetime was 138·8 g m^?2. The ratio between total production and mean biomass was given by P/B: 7·3.