0 1996, by the American Society of Limnology and Oceanography, Inc. The interrelationship of copepod fecundity and mortality

The fecundity of copepod species that carry attached eggs is commonly assessed by the egg ratio (eggs female-l), whereas the fecundity of broadcast-spawning copepods is assessed by measures of daily per capita rates of egg production. Variability in these measures, when corrected for temperature and allometric rela-tionships with body size of adult females, is often assumed to reflect variability in food supply in nature and to thus provide an index of food limitation of population growth and of secondary production. We show that the measured fecundity of both brooding and broadcast-spawning copepods is affected by the mortality rate of adult females. We recognize three reproductive stages of adult female copepods: prereproductive, reproductive, and postreproductive. Mortality affects realized fecundity by shifting the relative abundance levels in these stages. Changes in mortality rates can generate substantial temporal variations in measured fecundity, even for copepods that are unlimited by ambient food supply and reproduce at physiological maximum rates. To correct for the effects of mortality on realized fecundity, precise experimental deter-mination of the reproductive schedule of adult females is needed, along with measures of mortality rates in nature. Variability in the egg production rate (EPR) of plank-tonic copepods is an important demographic parameter in any quantitative description of population growth. EPRs are relatively easily measured in the field by incubating adult females in natural particle suspensions. Such mea-surements provide a useful instantaneous rate term de-rived from natural populations. Because the EPR can be proportional to rates of juvenile somatic growth, at least for broadcast-spawning copepods (Sabatini and Kiorboe 1994; McLaren and Leonard 1995), copepod EPRs have also been used as measures of secondary production (e.g