Workpackages

The application of the morphometric analysis produce interesting results for stock delineation purposes. A statistically significant number of specimens (at least 100) from each site or location (see map) will be analysed to isolate body and otolith shape differences among areas or samples. All the samples taken will be sent to Partner 02 for body shape analysis. After the parasitological analysis (see diagram of material flow), Partner 07 will remove the otoliths from these specimens to send them to Partner 10 for otolith shape analysis. Each sampled specimen and otolith will be treated as a multivariate observation and the application of multivariate statistical techniques will enable to distinguish if the differences among areas are greater than within samples. The shape analysis technique is easy and fast for data collection and one of the more powerful techniques for the interpretation of patterns of variation below species level. On the other side, the results must be carefully checked for both their statistical and biological significance. The application of other techniques simultaneously will help in obtaining this significance for stock delineation purposes.

One confounding effect influencing the interpretation of between-area differences in otolith shape is the fact that the otoliths change their shape considerably with increasing age (see animation [ageview2.gif]). Thus, correction factors, accounting for allometric growth, will have to be applied before analysing geographical differences in otolith shape as a tool for stock separation.

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