ASSESSING THE EQUIVALENCE OF GROWTH AND EGG-PRODUCTION OF COPEPODS

The hypothesis that food-saturated rate of production of egg matter is equivalent to maximal specific growth rate of copepods has not been w idely tested, and seems contradicted by some studies. If verified, it would supply, for example, a single P/B ratio for all stages where foo d is adequate in nature. We test the hypothesis using published data o n Calanus species. Logically, rate of production of egg matter at give n temperatures should be expressed as a function of structural body ma ss, with storage lipid and ovary weight discounted. This can be compar ed with growth rates of younger copepodid stages, based on lab-determi ned temperature functions for times to reach mid-stages, together with weights from nature or single rearing experiments. Growth of later st ages is more relevant, but difficult to assess adequately in the labor atory. We show how body sizes of females, known to be negatively relat ed to temperature, might be used to correct for reduced growth rates i n these later stages. Our assumptions and approximations appear to pre dict quite well the temperature-dependent daily rates of egg productio n of fully reproductive, well-fed females of four species of Calanus, and we suggest ways of obtaining and presenting data to test the hypot hesis more thoroughly. (C) 1995 International Council for the Explorat ion of the Sea