Age- and size-dependent growth and mortality in a population of Fucus distichus

Abstract

In a Fucus distichus population at False Creek, Vancouver, mean length was greater in winter (4.2-5.3 cm) and lower in summers of 1986 and 1987 (2.7-4.3 cm). Absolute growth rates showed a significantly opposite trend, being higher in spring and summer (0.24-1.17 cm mo-1) and lower in fall to winter (-0.5 to 0.4 cm mo-1). With some exceptions, monthly patterns of change in plant mean length for plants of different ages were significantly correlated, but growth rates were not significantly correlated among ages. Patterns of change in length among cohorts were significantly correlated, but those of growth rates were not, suggesting a low dependence of growth rate on age. Growth rate appears to be strongly size-dependent. Plants from different cohorts generally had constant rates of mortality. Mortality was generally higher for younger and smaller plants during winter and spring, and for older and larger plants during summer. Older plants also exhibited higher mortality in the fall. Size is shown by association analyses to be a better predictor of growth and mortality than age. -from Author