RECRUITMENT AND THE LOCAL DYNAMICS OF OPEN MARINE POPULATIONS

The majority of marine populations are demographically open; their rep lenishment is largely or exclusively dependent on a supply of juvenile s from the plankton. In spite of much recent research, no consensus ha s yet been reached regarding the importance of recruitment relative to other demographic processes in determining local population densities . We argue 1. that demographic theory suggests that, except under rest rictive and unlikely conditions, recruitment must influence local popu lation density to some extent. Therefore, 2. the question as to whethe r the size of a particular population is limited by recruitment is mis guided. Finally, 3. the effect of recruitment on population size can b e difficult to detect but is nonetheless real. A major weakness of mos t existing studies is a lack of attention to the survival of recruits over appropriate scales of time and space. Acknowledgment of the multi factorial determination of population density should guide the design of future experimental studies of the demography of open populations.