Environmental and genetic determinant of otolith shape revealed by a non-indigenous tropical fish

Otolith morphometrics have been shown to provide a practical basis for stock discrimination and subsequent fisheries management. However, the determinants of otolith shape are not fully understood and analysis does not distinguish between genotype and environmentally induced differences. In this context, understanding how those 2 components act synergetically on the otolith shape is fundamental. The use of non-indigenous fish of multiple origins provides an interesting tool for evaluating the relative importance of genetic and environmental components in determining otolith shape. This paper investigates to what extent a dual regulation (i.e. genetic and environmental) of the otolith shape from an introduced coral reef snapper (Lutjanus kasmira) exists, in order to determine how each component specifically acts on otolith morphology. Using geometric morphometrics, we discriminated between native and introduced range as well as between individuals belonging to different lineages (i.e. origins) but growing under the same environmental conditions (individuals cohabiting within the same shoals in the wild). Here we show that both genetic and environmental influences play a substantial role in determining the shape of the otolith. More specifically, while environment induces an overall change in otolith shape, genetically induced changes locally affect otolith shape. In addition, data suggest that both nuclear and mitochondrial components act synergetically. This information is fundamental if otolith shape is to be used as an effective tool for management of fisheries resources in the future.