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Implicit in past studies of recruitment is the assumption that all new recruits possess the same capacity for juvenile growth, and that observed variation in juvenile growth and survival is due entirely to spatial and temporal variation in food availability, magnitude of physical stresses, and intensity of competition and predation. We set out to determine if daily larval cohorts of the barnacle Semibalanus balanoides differ in mean physiological quality and, therefore, in their potential for recruiting to adult populations. To assess larval physiological quality, we measured the organic content of nonfeeding cyprid larvae attaching on five dates (10-15 d intervals) during the 1995 recruitment season. Juvenile physiological quality was determined by monitoring the growth, under controlled laboratory conditions, of individuals attaching on seven dates (3-15 d intervals) during the same season. Both cyprid organic content and juvenile growth capacity differed significantly among daily cohorts. We suggest that variation in cyprid organic content may explain previous observations of temporal variation in cyprid metamorphic success and early juvenile mortality and further suggest that variation in juvenile growth capacity contributes to differences in recruitment success of daily cohorts.

Planktonic larvae of marine organisms may vary greatly in individual condition. Larval quality, metamorphosis, juvenile growth, and mortality of the barnacle Semibalanus balanoides were monitored in the field and laboratory for 4 mo to determine whether propagule quality varied among daily cohorts and influenced juvenile performance. I measured the organic content of individual planktonic cyprids sampled on 15 days during the recruitment season. Settlers were monitored daily on natural substrata in the field and on settlement plates deployed daily and transferred to the laboratory. Cyprid organic content declined as the recruitment season progressed. Metamorphic success and growth differed among cohorts in both the field and laboratory. Mortality differed among cohorts in the field, but no mortality occurred in the laboratory. Metamorphic success and growth increased with increasing cyprid organic content in the laboratory. Growth in the laboratory was high for the first 7 of 10 daily cohorts monitored. In the field, the first and last three cohorts of the season grew poorly even though cyprid organic content was greater for the first three cohorts. These findings indicate that larval quality can vary among cohorts and impact juvenile performance. Studies of population and community structure may benefit from consideration of propagule quality. Corresponding Editor: S. G. Morgan.

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