Estimation of larval fish prey volume: mensuration formulae for copepod nauplii

ISSN： 1464-3774

Source： Journal of Plankton Research, Vol.21, Iss.9, 1999-09, pp. : 1633-1642

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Abstract

Prey volume measurements are used to determine feeding bioenergetics and transfer of energy between trophic levels. Quantitative estimation of larval fish feeding success often depends on accurate estimates of prey volume inside the gut. Many marine fish larvae begin their lives feeding on copepod nauplii. Various methods and formulae have been proposed to estimate bodily volume of this diverse and difficult to identify group of organisms. We estimated the mean square error and average error for six different single-measurement formulae used to calculate bodily volume for two stages (NI and NIV) of three different copepod genera found in the eastern Bering Sea (Metridia, Oithona and Pseudocalanus). Each method used an assumed or empirical relationship among the three bodily dimensions (length, width and depth). Methods that assume a single geometric model and fixed bodily proportions for al nauplii are shown to be poor estimators of bodily volume. Mensuration methods must take into account the variety of body forms and changes in proportions during development for accurate estimation of bodily volume. It is possible, however, to reduce the number of measurements needed (i.e. to assume fixed bodily proportions) if one accounts for differences among taxa and developmental stages.