Evaluation of otolith shape variability in hatchery-reared brook trout (Salvelinus fontinalis), Black Sea trout (Salmo trutta labrax) and their hybrid

In aquaculture, the process of hybridization is used to produce animals that have better growth rates, meat quality, and higher resistance and tolerance to environmental variations than their parental species. The identification of a hybrid fish may require a DNA-based technology that is an expensive process. In this study, the sagittal otolith shape of hatchery-reared brook trout (Salvelinus fontinalis), Black Sea trout (Salmo trutta labrax) and their hybrid (S. fontinalis ♂ × S. t. labrax ♀) were studied and compared to elucidate the variation between their morphometric values. The otoliths were measured by image analysis and used to calculate shape descriptors: form-factor, roundness, and aspect ratio. Based on the morphometric measurements, the hybrid fish were not statistically intermediate between the parents and share most of the similarities with the female parent. The relationships between fish size and otolith size were best described by the exponential function (>r2=0.90).