Relation between Biomass, Productivity, and Loss to Predators in a Population of a Marine Benthic Polychaete, Pectinaria hyperborea

Abstract

The changes in population density and individual size distribution in a population of the trumpet worm Pectinaria hyperborea Malmgren were observed on eight occasions in 20 months at a station 60 m deep on a soft muddy substrate in St. Margaret's Bay, N.S. Production proceeded rapidly during the early life stages while loss due to mortality (elimination) was low, so that biomass increased and reached a maximum at 170 days. Between 30 and 370 days the rate of elimination was nearly constant at about 0.9 g/m² wet weight per 50-day period in spite of changing biomass. After 370 days the rate of production, rate of elimination, and biomass decreased. It was estimated that 80% of mortality was due to predation. Almost 90% of total production of the cohort took place in the first year of life. The ratio between annual production and biomass present in May 1967 in the study area was used to estimate annual production at 24 stations in the bay.