Morphological traits allow distinguishing their hybrids from the Northern pike, Esox lucius, and the Aquitanian pike, Esox aquitanicus (Actinopterygii, Esociformes)
The Aquitanian pike Esox aquitanicus is an endemic species of the South-West of France. It is threatened by the hybridization with the Northern pike Esox lucius. So far, hybrid determination was established with molecular tools only. The purpose of this study is to find morphological traits in order to differentiate hybrids from the two parental species; we looked at the three criteria distinguishing E. aquitanicus from E. lucius: skin colour pattern, lateral scale numbers and snout length. Our results showed that hybrids can actually be distinhguished from E. lucius (shorter snout and fewer lateral scales) and E. aquitanicus (higher lateral scales count). The skin colour pattern is however irrelevant, as the pattern of both species is encountered among hybrids. Finally, the best trait to identify hybrids is the lateral scale number, which is intermediate between those of the parental species (114 to 119 vs. 104 to 107 for E. aquitanicus and (115)120 to 136(146) for E. lucius). This could be helpful for managers in the conservation of the Aquitanian pike. Nevertheless, the results of this study need to be confirmed with a larger sampling.