Discriminant Geographic Variation of Saccular Otolith Shape and Size in the Common Pandora, Pagellus erythrinus (Sparidae) across the Gulf of Gabes, Tunisia

A total of 243 Pagellus erythrinus saccular otoliths' shape and size, including length, width, area, and perimeter, were examined among individuals of the Chebba, Sfax, Gabes, and Zarzis stations located in the Gulf of Gabes, Tunisia. The objective was to assess the geographic variation in the otoliths' shape and size and the effect of potential fluctuating asymmetry in otolith size on the stock structure of P. erythrinus individuals from these stations. Analysis of the otolith shape showed a statistically significant difference (Wilks' lambda = 0.1661, p < 0.0001), i.e., asymmetry, in the left and right otoliths shape among individuals of the four stations, as well as among those within the Chebba and Gabes stations. Besides, a significant shape difference was observed in the left-left and right-right otoliths among individuals of both Chebba and Gabes, Chebba and Zarzis, Gabes and Sfax, Gabes and Zarzis, and Sfax and Zarzis stations. Moreover, a significant fluctuating asymmetry was detected in width between the left and right otoliths only among individuals of the Sfax and Gabes stations. Discriminant function analysis of the otoliths' contour shape confirmed the presence of three separate main stocks, one corresponding to the Chebba and Sfax stations, the second representing Gabes, and the third characterizing Zarzis, which should be managed separately.

Automated summary

The study examined the shape and size of otoliths in Pagellus erythrinus from different stations in the Gulf of Gabes and found significant differences and asymmetry in shape among individuals and stations. Discriminant function analysis identified three separate stocks that should be managed separately: Chebba and Sfax, Gabes, and Zarzis.