Stock discrimination of two insular populations of Diplodus annularis (Actinopterygii: Perciformes: Sparidae) along the coast of Tunisia by analysis of otolith shape

Abstract

Background. The annular seabream, Diplodus annularis (Linnaeus, 1758), is the most common sparid fi sh in the Mediterranean Sea. This species is widespread in Tunisia. Despite their economic importance, due to their excellent white and delicate fl esh (demersal fi sh) and their signifi cant size, few studies have hitherto focused on stock discrimination and on the fi sheries management. The goal of this research was to evaluate the stock structure of D. annularis for two Tunisian insular populations based on the otolith shape, using different statistical approaches. Materials and methods. The specimens of Diplodus annularis were collected during fi ve months ranging from May through September 2014 at two sites: Djerba and Kerkennah. In total, 120 fi sh were collected from the two sites: 60 specimens of each population (30 males and 30 females) and were included in different statistical analyses. The Fourier coeffi cients were determined to evaluate the degree of similarity in the otoliths and detect the reciprocal variability. Results. By comparing the two studied populations, we revealed statistical signifi cant differences, an asymmetry (left-right), of otoliths (P < 0.05). In the same population, symmetry (left-right) was detected for the males, females of Kerkennah, and females of Djerba. However, an asymmetry was detected only for the males of Djerba. Also, sexual dimorphism was observed only for the Djerba population. Conclusion. The comparison of the otolith morphology of the two populations showed a clear difference in shape and a left-right asymmetry of otoliths. This asymmetry indicates that the two populations belong to different stock of fi sh. The stocks characterization is considered as an important tool for fi sheries management. Further studies are necessary to determine the origin of the otolith shape differences and whether they are related only to environmental conditions or a genetic basis may also be responsible.

Use of otolith-shape analysis for stock discrimination of Boops boops along the Algerian coast (southwestern Mediterranean Sea)

“…Such otolith-shape differences between the right and left inner ears are common in flatfish species (Mérigot et al 2007;Mille et al 2015), due to body morphology asymmetry and lateralised behaviour. These differences are usually not observed for roundfish (Panfili et al 2002;Lychakov and Rebane 2005), although some differences were reported in species such as whiting Merlangius merlangus (Mille et al 2015) and annular seabream Diplodus annularis (Trojette et al 2015). Differences observed in roundfish species are difficult to explain and further studies are needed to improve knowledge on otolith biomineralization and the physiological mechanisms that produce changes in otolith asymmetry (Mille et al 2015).…”

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

“…Up to now, some studies have been conducted on the otolith shape variability in some Tunisian sparid species such as Diplodus annularis (Linnaeus, 1758) (see Trojette et al 2015) and Pagellus erythrinus (Linnaeus, 1758) (see Mejri et al 2018) cohabiting different habitats. However, no studies have been carried out on the bogue, B. boops.…”

Changing Isotopic Food Webs of Two Economically Important Fish in Mediterranean Coastal Lakes with Different Trophic Status

“…In the Mediterranean area, the European eel, Anguilla anguilla (Linnaeus, 1758), and the annular seabream, Diplodus annularis (Linnaeus, 1758), are widespread and among the most important fishery resources [15,16]. However, in the last two decades, European eel populations have collapsed due to low recruitment and habitat alteration, and the species has been classified as 'critically endangered' since 2014, according to the International Union for Conservation of Nature [17].…”