Defining length-at-metamorphosis in fishes: a multi-character approach

Abstract

The present study attempts to highlight the value of multi-character approaches for defining thresholds in fish ontogeny, like the onset of the juvenile period. We developed techniques to objectively define the transition from larval to juvenile development using morphometric as well as morphological characters and exemplify the multi-character approach on newly settled white sea-breams (Diplodus sargus sargus) collected from the eastern Mediterranean. The morphometric analysis was based on principles of multivariate allometry whereas the analysis of morphology, on assigning a suite of selected characters (here related to external morphology and osteological development) into larval, transforming and juvenile states. The size-at-change in multivariate allometric growth (L m) is considered here to denote mean length-at-metamorphosis. An almost perfect match is demonstrated between L m (‘multivariate morphometry’) and mean size-at-morphological change (‘multivariate morphology’) in white sea-bream.