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.