Deformities in larval gilthead sea bream (Sparus aurata): A qualitative and quantitative analysis using geometric morphometrics

Deformities in commercially raised fish are a common source of downgrading of product value. During the intensive rearing of gilthead sea bream (Sparus aurata), opercular deformities are the most commonly observed type of deformation (affecting up to 80% of the fisheries stock), sometimes showing a severe inward folding of the operculum. They are non-lethal malformations that appear during the larval stage but affect growth rate and morphology, with a significant economic loss as a consequence. In order to exploratory quantify and qualify these deformities, geometric morphometric analyses were performed on the external morphology from larvae with an age ranging from 50 to 69 days post-hatching (DPH), and on the cranial skeleton of 110 DPH old juveniles. The results showed several osteological cranial shifts and a striking left–right independency associated with deoperculation. Even though a significant size difference was observed at 65 DPH between normal and deoperculated specimens, allometries during the examined growth stages still appear to be very similar in normal and deoperculated specimens. At 69 DPH deoperculated specimens differed significantly from the normal specimens in their external morphology based on its shape variables, but the results suggest that discrimination is possible from earlier stages. Further analyses are needed, but the usefulness of this approach towards developing an early detection tool could be demonstrated.