Variability of Otolith Morphology and Morphometry in Eight Juvenile Fish Species in the Coastal Eastern Adriatic

Abstract

Sagittae otoliths of eight juvenile species: Boops boops, Diplodus vulgaris, Diplodus puntazzo, Sarpa salpa (family Sparidae), Liza ramada, Liza aurata (family Mugilidae), Atherina boyeri, Atherina hepsetus (family Atherinidae) were analysed and compared using descriptive morphological characters and morphometric indices. The noticeable differences among the otoliths of the investigated species are in their overall shape, margins (i.e. irregular, sinuate or crenate) and anterior region. Otolith shape varied from elliptic to pentagonal in sparids, elliptic to rectangular in mugilids and elliptic in two atherinids. Aspect ratio (OW/OL), ratio of the sulcus length occupied by the cauda length (CL/SL) and ratio of the sulcus length occupied by the ostium length (OSL/SL) were calculated for all species. The otolith contour was described using wavelets. The Canonical Analysis of Principal Coordinates (CAP) gave an overview of the otolith shape differentiation between eight juveniles. Using the Wavelet coefficients, the first principal component (CAP1) explained 58.1% of the variation among species and the second principal component (CAP2) 25.2%.

Stock discrimination of the bogue, Boops boops (Actinopterygii: Perciformes: Sparidae), from two Tunisian marine stations using the otolith shape

“…Furthermore, some authors have reported that age and sex may induce a significant difference in the otolith shape in fish stocks . As a result, Ferri et al (2018) found that the otolith shape is significantly different in juveniles from that in adults due to differences in the hearing function. However, it is noteworthy to mention herein that the sampling was only restricted to adult samples of B. boops to eliminate the confounding effect of allometric growth on the otolith form (Mejri et al 2020).…”

“…Also, Ider et al (2017) analyzed the variability of otolith shape in three populations of B. boops collected from the Algerian coast and observed a significant difference between the left and right otoliths and added that the shape is influenced by the fish length and the sampling location, but it is not related to sex and age. In addition, Ferri et al (2018) studied the variability of the otolith morphology and morphometry in six juvenile specimens collected from the eastern coastal Adriatic region and recorded variations in the sagittae shape, margins, and anterior region among the studied juveniles. Moreover, Mahé et al (2019) analyzed the directional bilateral asymmetry of otoliths in specimens collected from 11 geographical regions from the Canary Islands to the Aegean Sea using elliptical Fourier descriptors and found a significant otolith bilateral asymmetry at the global scale and non-significant asymmetry at the scale of sampling locations.…”

“…Consequently, otolith shape remains unaffected by short term changes in fish condition or environmental variations (Campana and Casselman 1993). Recent studies have shown that the saccular otoliths (sagittae) display high specific interand intra-variability in shape and size (Ferri et al 2018). Thus, they have been widely used as an effective tool to identify fish species and populations and to discriminate their stocks in different habitats (Jawad et al 2018).…”

“…Indeed, the external contour or shape of the otoliths has been studied by using several techniques, including univariate descriptors such as shape factors that include roundness or circularity (Tuset et al 2003), geometric morphometrics (Vergara-Solana et al 2013), wavelet functions (Ferri et al 2018), growth markers (Benzinou et al 2013), curvature scale space (Mapp et al 2017), and geodesic methods (Benzinou et al 2013). Although, the elliptical Fourier analysis (EFA) remains the most widely used method for describing and characterizing outlines, capturing outline information efficiently in a quantifiable manner has been widely used to describe the variation of the otolith shape between fish species in stock discrimination and analysis of population structure of diverse species (Mahé et al 2019).…”

Use of otolith morphology and morphometry for species discrimination of megrims Lepidorhombus spp. in the Central Eastern Adriatic Sea

“…An advantage of otolith shape analysis is that if the discrimination between species is statistically significant, it can be more advantageous as a monitoring tool, because of its relatively low cost, easy preparation procedures (Christensen et al ., 2018) and most importantly for improving accuracy and precision in determining age. Otolith shape analyses have been successfully applied to a number of species (Capoccioni et al ., 2011; Škeljo & Ferri, 2012; Ferri et al ., 2018).…”