For the first time, saccular otolith shape and size were analysed in 254 samples of the bogue Boops boops collected from the marine stations of Bizerte and Kelibia situated in north-east Tunisia. The objectives were (1) to examine the inter- and intra-population variation in the otolith shape and size, including length (Lo), width (Wo) and area (Ao) measurements, and (2) to assess the relationship between otolith mass asymmetry (OMA) and total fish length (TL). In addition, the impact of pollution present in these two stations on the shape and size of the otolith in relation to the TL was discussed. Analyses of the otolith shape and biometric data showed a statistically significant asymmetry in the otolith shape (P < 0.0001) between the right and left sides within the population of Bizerte, as well as between the otoliths from the same right-right and left-left sides between the populations of Bizerte and Kelibia. Similarly, a significant Wo asymmetry (P < 0.05) was recorded within the population of Kelibia. Conversely, a significant symmetry was detected in Lo and Ao (P > 0.05) between the right and left sides within the populations of Bizerte and Kelibia. Moreover, the level of asymmetry of Ao was higher than that of Lo and Wo in both populations. Nevertheless, Student's t-test showed no statistically significant differences (P > 0.05) for Lo, Wo and Ao in relation to the means of TL between the three groups of the populations of Bizerte and Kelibia, although significant differences (P < 0.05) were found by using box plots. Furthermore, no statistically significant relationship (P > 0.05) was detected between OMA and TL within and between the populations of Bizerte and Kelibia. The possible cause of fluctuating asymmetry (FA) in the otolith shape and size both within and/or between populations of the two stations has been discussed in relation to the instability of development induced by environmental stress associated with the variation in water temperature, salinity, depth, feeding conditions and pollutants present in these stations.

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The variability of 14 morphometric and seven meristic characters of Boops boops (L.) collected at four stations along the Tunisian coast was examined in 518 samples ranging from 126 to 206 mm in total length and 37 to 78 g in total weight. Statistical analysis of both sets of characters showed significant variation among the four populations in 13 (92.9%) morphometric and four (57.1%) meristic characters. CVA and cluster analysis of the morphometric characters revealed four groups corresponding to four populations, with 95.36% correct classifications of individuals to their populations of origin. However, CVA and cluster analysis of the meristic characters showed a reticulate relationship among the four populations, as there was clear differentiation between those in Monastir and Zarzis and an overlap between those in Bizerte and Kelibia, with only 51.75% of individuals correctly classified to their respective populations. This morphological differentiation among the populations from the four stations was attributed to the differences in the physico-chemical water properties at these stations. However, further studies are needed on the impact of environmental factors and diet at these stations on the morphological population structure of B. boops to better understand the contribution of environmental conditions to morphological variation.