The use of otolith shape and morphometry for identification and size-estimation of five wrasse species in predator-prey studies

Sagittal otoliths of five wrasse species, Coris julis, Symphodus tinca, Symphodus cinereus, Symphodus ocellatus and Symphodus rostratus from the eastern Adriatic were compared using descriptive morphological characters (types of anterior and posterior otolith regions and otolith margins) and shape indices (formfactor, roundness, circularity, rectangularity and elipticity). All shape indices except the formfactor were used to build the discriminant function, with circularity and roundness being the main variables that explain the interspecific variability. The overall classification score of the discriminant analysis was 62.8%, with the lowest score obtained for S.similar to ocellatus (44.3%) and the highest for C.similar to julis (83.3%). Otolith morphometric parameters (length, width, thickness and weight) were used in predictive linear regression equations to estimate fish size. For all investigated wrasses, except for S.similar to rostratus, otolith length showed the strongest and otolith thickness the weakest relationship to both fish length and weight. Multiple linear regression equations based on log transformed variants explained higher proportion of variation in fish size than simple linear regressions, although these differences in R2 were relatively low, amounting to 1.312.1% when compared to the best simple regressions for different species.