Esox cisalpinus

Esox cisalpinus (southern pike) is a freshwater fish restricted to freshwater habitats in central and northern Italy (Southern Europe). As with the widespread northern pike Esox lucius, the southern pike is an important species for recreational and commercial fisheries, and for its role as top predator in freshwater ecosystems.

Esox cisalpinus was distinguished from Esox lucius and described scientifically as a new species in 2011 independently by two research groups. The description by Bianco & Delmastro was printed earlier, and the name Esox cisalpinus is therefore accepted, whereas the alternative name published somewhat later by Lucentini et al., Esox flaviae, is considered a junior synonym.

Lucentini et al. explicitly tested the hypothesis that the different phenotypes of the pike, geographically isolated in Europe, represent two different evolutionary entities. They analysed phenotypic and genetic differences, e.g. in the skin colour pattern and in meristic characters such as the number of scales in the lateral line, which distinguish the two species. They applied a coalescent-based approach to mtDNA phylogeny and evaluated the degree of historical admixture, testing overall genetic differences from amplified fragment length polymorphism (AFLP). The Italian southern pike turned out distinct from the northern pike, whose range extends from central and northern Europe across Asia to North America.

The authors recommend stopping the stocking of pike in southern Europe using northern pike from other European countries, as this could greatly impact the survival of this newly discovered species in its native range.