Otolith shape discrimination of Liza ramada (Actinopterygii: Mugiliformes: Mugilidae) from marine and estuarine populations in Tunisia

Abstract

Background. The thinlip grey mullet, Liza ramada (Risso, 1810), is widespread in Tunisia. Despite its economic importance, the stock discrimination of this fish is poorly understood. The aim of this study is to investigate, for the first time, the stock discrimination of this species for two Tunisian populations based on the otolith shape, using different statistical approaches. Materials and methods. The specimens of L. ramada were collected during three months (from March to May 2013) at two sampling sites: the marine (Cap Zebib sea resort) and the estuarine (Mellegue Dam) in Tunisia. We analysed sagittal otolith shape variation for 120 individuals (60 fish of each study site comprising 30 males and 30 females) for both sexes (males and females) and two sides (left and right otolith) for each specimen. Results. Statistical-and discriminant function analysis of the sagittal otolith shape clearly demonstrated statistically significant differences from the two populations. These results were also confirmed by highly statistically significant difference between otolith shape (left and right) for both sexes. An asymmetry was detected when comparing otoliths of the same side (RR-LL) between different sampling sites. Conclusion. The shape variability of otolith between these two sampling sites is probably correlated with local environmental and ecological factors.

Directional bilateral asymmetry in otolith morphology may affect fish stock discrimination based on otolith shape analysis

“…DA between right and left otolith shapes was previously described for other roundfish species such as Liza ramada (Rebaya et al, 2017), Diplodus annularis (Trojette et al, 2015), Diplodus puntazzo (Bostanci et al, 2016), Clupea harengus (Bird et al, 1986) and Scomberomorus niphonius (Zhang et al, 2016). Conversely, symmetry between left and right otolith shapes was observed for other fish species: Gadus morhua (Cardinale et al, 2004;Petursdottir et al, 2006), Synechogobius ommaturus (Wang et al, 2011),…”

Otolith fluctuating asymmetry inBoops boops(Actinopterygii, Sparidae) from two marine stations (Bizerte and Kelibia) in Tunisian waters

“…This is because fish species are very sensitive to temperature variations and respond to a change of only 0.03°C (Trojette et al ., 2015). In addition, salinity can directly affect the habitats and indirectly affect the chemical composition and shape of the otoliths (Rebaya et al ., 2017). Moreover, Martin & Wuenschel (2006) claimed that the variation in the chemical composition of the otolith is probably related to the differences between the responses of the individuals to the influence of the salinity interaction on temperature and the concentration of some common elements, such as Cl, Mg, K, Na and Ca.…”

“…During the last decades, study of the morphological characteristics of otoliths, in particular their shape, length, width, area, thickness and weight, has been used to test both genetic and environmental stressors and as a bioindicator to test the differentiation of populations and the variance in stock discrimination studies using Elliptical Fourier analysis (EFA) (Valentine et al, 1973;Campana & Casselman, 1993;Begg & Waldman, 1999;Torres et al, 2000;Smith et al, 2002;Panfili et al, 2005;Turan, 2006;Jawad et al, 2010Jawad et al, , 2011Jawad et al, , 2012aJawad et al, , 2012bJawad et al, , 2012cJawad et al, , 2016Jawad et al, , 2020Vignon & Morat, 2010;Cañás et al, 2012;Jawad, 2012Jawad, , 2013Lord et al, 2012;Treinen-Crespo et al, 2012;Mahe et al, 2014;Trojette et al, 2014Trojette et al, , 2015Abu El-Regal et al, 2016;Brophy et al, 2016;Hüssy et al, 2016;Rebaya et al, 2016Rebaya et al, , 2017Al-Busaidi et al, 2017;Fatnassi et al, 2017;Ider et al, 2017;Khedher et al, 2017;Rodgveller et al, 2017;Chakour & Elouizgani, 2018;Khemiri et al, 2018;Kontaş et al, 2018;Mejri et al, 2018;Wang et al, 2018;…”

“…In the context of the influence of environmental factors on the shape of the otolith, several authors have suggested that environmental factors, such as water temperature, salinity, food availability, depth, and substrate type are the main factors that are likely to be responsible for the differences in otolith shape between conspecific individuals (Begg & Brown, 2000;Torres et al, 2000;Cardinale et al, 2004;Gagliano & McCormick, 2004;Mérigot et al, 2007;Hüssy, 2008;Morat et al, 2012). In Tunisian waters, recent investigations have described that the otolith shape is likely correlated with the variation in environmental conditions (Trojette et al, 2014(Trojette et al, , 2015Rebaya et al, 2016Rebaya et al, , 2017Fatnassi et al, 2017;Khedher et al, 2017;Khemiri et al, 2018;Mejri et al, 2018Mejri et al, , 2020Ben Mohamed et al, 2019;Jmil et al, 2019).…”

“…During the last decades, study of the morphological characteristics of otoliths, in particular their shape, length, width, area, thickness and weight, has been used to test both genetic and environmental stressors and as a bioindicator to test the differentiation of populations and the variance in stock discrimination studies using Elliptical Fourier analysis (EFA) (Valentine et al ., 1973; Campana & Casselman, 1993; Begg & Waldman, 1999; Torres et al ., 2000; Smith et al ., 2002; Panfili et al ., 2005; Turan, 2006; Jawad et al ., 2010, 2011, 2012 a , 2012 b , 2012 c , 2016, 2020; Vignon & Morat, 2010; Cañás et al ., 2012; Jawad, 2012, 2013; Lord et al ., 2012; Treinen-Crespo et al ., 2012; Mahe et al ., 2014; Trojette et al ., 2014, 2015; Abu El-Regal et al ., 2016; Brophy et al ., 2016; Hüssy et al ., 2016; Rebaya et al ., 2016, 2017; Al-Busaidi et al ., 2017; Fatnassi et al ., 2017; Ider et al ., 2017; Khedher et al ., 2017; Rodgveller et al ., 2017; Chakour & Elouizgani, 2018; Khemiri et al ., 2018; Kontaş et al ., 2018; Mejri et al ., 2018; 2020; Wang et al ., 2018; Ben Mohamed et al ., 2019; Fashandi et al ., 2019; Jmil et al ., 2019; Mahé et al ., 2019; Puentes et al ., 2019; Osman et al ., 2020). Indeed, these studies have shown that the otolith shape is species-specific (Sadighzadeh et al ., 2014) and that variability in the otolith shape, structure and development is influenced by ontogenetic, genetic and environmental factors (Campana & Casselman, 1993; Cardinale et al ., 2004; Vignon & Morat, 2010; Vignon, 2015; Hüssy et al ., 2016; Ider et al ., 2017; Fashandi et al ., 2019), as well as by sex, growth, maturity and pattern of fishery exploitation (Begg & Brown, 2000), or by individual characteristics, e.g.…”