Based on the change in the allometric relations between the antennular spine and body length in the passage from Furcilia VI to juvenile in Euphausia superba lineal discriminant functions have been constructed to classify damaged specimens, specially those coming from penguin stomachal contents. Body, Telson and antennulars lengths are used. Misclassification probabilities have been calculated on an independent sample resulting reasonably low (3 out of 28 specimens). Body and Telson lengths resulted highly correlated (R=0.95); allowing the use of the method when body length is not available.
Abstract:
Penguins selectivity for krill size is shown as highly sensitive to the statistical assumptions made in the analysis of data. Nested designs are proposed as the correct approach because lack of independence between krill found in the stomach of a given penguin prevents the pooling of krill lengths from different samples.
Samples taken at Bahía Esperanza are used to illustrate the different approaches. A highly significant linear regression between krill size and time was found.
Full use of the information contained in stomachal contents requires the use of block sampling designs. Replicating samples of the same penguin or the study of length distributions of the various (according to digestion degree) fractions of stomachal contents are proposed as alternative methods.
