New Proposed Species—Five known species of Esox currently inhabit North America, Europe, and Eurasia. Among these, the northern pike (Esox lucius) is circumpolar and believed to consist of a single species. Analysis of individuals from southern Europe, however, suggests the existence of a separate species, with the proposed name of southern pike (Esox flaviae).* Researchers examined pike samples from continental Europe, northern Italy, and central Italy. Declines in populations in Mediterranean countries, and concerns about stocking pike there from northern Europe with associated concerns about maintaining genetic diversity, were among the reasons for this study.
Analysis of pike included comparisons of genetics and morphology, and the differences observed supported the differentiation of two species between the northern and southern pike groups. The strongest discrimination is the number of scales along the lateral line, which ranges from 101 to 115 in southern pike and 125 to 148 in northern pike. The two species also differ in color pattern, with the southern pike exhibiting four patterns including stellate spot, and diagonal, longitudinal, or vertical bars. They never display the round spot color pattern of northern pike. The authors suggest the correct identification of these two species raises concerns about stocking northern pike in waters with southern pike, due to potential problems with hybridization.
*Lucentini, L. , and 8 co-authors. 2011. Molecular and phenotypic evidence of a new species of genus Esox (Esocidae, Esociformes, Actinopterygii): the southern pike, Esox flaviae. PLoS ONE 6(12): e25218.