ABSTRACT
Urchin population structure was examined over a period of 5 y at an urchin dominated site in eastern Newfoundland, in relation to depth, inter-annual variation, and microhabitat. The distribution of juveniles was the main focus of the study. Juvenile urchin density was low in the two zones with abundant macroalgae (0-2m and > 12m below MLW), and highest in the barrens which occur at intermediate depths. Juvenile urchins were abundant during 1979-1980, but declined over the period from 1981-1983. There is evidence for high predation rates on juveniles. Nevertheless, by inhabiting cryptic micro-habitat beneath undercut corallines and among the uprights of Lithothamnion glaciale, enough survive to maintain the dense population of large urchins, whose grazing maintains the barrens.
