The description of Esox cisalpinus, based on specimens from Torino in northern Italy, was published four days prior to that of Esox flaviae (Puletti, Ricciolini, Gigliarelli, Fontaneto, Lanfaloni, Bilò, Natali & Panara 2011), based on specimens from Lake Trasimeno in central Italy.

E. flaviae was later synonymised with E. cisalpinus (Bianco 2014), but some authors have disputed this conclusion and consider the former to remain valid (e.g., Gandolfi et al. 2016, 2017).

In addition, the species has for decades been widely crossed with the congeneric Northern Pike (Esox lucius) in aquaculture facilities and the resultant hybrids introduced to water bodies throughout Italy, much of Europe and the Mediterranean basin on an unchecked basis. Within its native range, these events have resulted in a patchy distribution whereby native or marginally-introgressed subpopulations are surrounded by a complex mosaic of non-native or hybrid lineages, thus hampering management and conservation efforts (Gandolfi et al. 2016).

Global and European regional assessment: Vulnerable (VU)
EU 27 regional assessment: Vulnerable (VU)

The Cisalpine Pike does not approach the range thresholds for Vulnerable under Criterion B1 (extent of occurrence (EOO) < 20,000 km²) or D2, and Criterion B2 is precluded by its uncertain area of occupancy (AOO). The population size is believed to exceed 10,000 individuals, therefore it does not approach the thresholds for Criteria C or D, and there exists no quantitative analysis which would permit the application of Criterion E.

Although no range-wide population trend data exists, a suspected ongoing reduction based on declining habitat quality and the effects of introduced taxa might approach or meet the threshold for Vulnerable or Endangered under Criterion A2 (≥ 30% or ≥ 50% over the past 48 years = three generations).

As a result of this data uncertainty, Vulnerable and Endangered are equally plausible Red List categories for the present assessment, and this species is assessed as Vulnerable (A2ce) both globally and for the EU 27 member states.

This species is endemic to northern and central Italy, where its range is understood to extend southward from the Po River to the Isonzo River in the Adriatic Sea basin, and from the Magra River to the Tiber River in the Tyrrhenian Sea basin. The species may occur in the Swiss part of the Po River system in southern Switzerland.

The precise limits of its distribution remains somewhat unclear. For example, there is an isolated record from the Trigno River, which drains to the Adriatic Sea at the border between the Abruzzo and Molise regions in southern Italy.

It has for decades been widely crossed with the congeneric Northern Pike (Esox lucius) in aquaculture facilities (see 'Threats'). The resultant hybrids have been introduced to water bodies throughout Italy, much of Europe and the Mediterranean basin on an unchecked basis, meaning neither an accurate description nor map of its non-native range could be produced within the scope of this assessment.

Within its native range, these events have resulted in a patchy distribution whereby native or marginally-introgressed subpopulations are surrounded by a complex mosaic of non-native or hybrid lineages, thus hampering management efforts (see 'Conservation').

This species' population size is unknown, but is understood to exceed the minimum threshold for Red List criteria (< 10,000 mature individuals). The current population trend has not been quantified, and the number of subpopulations is unclear.

Its overall abundance is understood to have declined significantly since the mid-20^th century, and this pattern is suspected to be ongoing to an as yet undetermined extent. For example, reports from the Piedmont region suggest that it was extirpated from c. 54% of known sites in the Po River system between the early 1990s and 2006.

At the subpopulation scale, it has been extirpated from fluvial Lake Piediluco in the upper Tiber River catchment, while fisheries statistics suggest that it has declined by at least 70% over the last 45 years (= c. three generations) in endorheic Lake Trasimeno.

These declines led to commercially-driven introductions of non-native pikes throughout its range, and as a result of subsequent introgressive hybridisation it is thought that only a relatively small number of genetically-intact populations remain (see 'Threats'). However, exhaustive sampling and genetic screening have not yet taken place.

This large-bodied species inhabits lentic and sluggish lotic habitats such as lowland rivers and stream channels, floodplains, and natural lakes. It prefers relatively clear, shallow water with submerged woody structures and dense macrophyte beds.

It is eurytopic and able to breed prolifically in artificial lakes, gravel pit ponds and canals while tolerating diverse physical and chemical water parameters, including variations in temperature, oxygen concentration, and pH.

Like other members of the genus Esox, it is an obligate ambush predator, employing a "sit-and-wait" hunting strategy and feeding primarily on other soft-rayed fishes. However, it also preys opportunistically on aquatic invertebrates, amphibians, small mammals, and waterfowl.

Cannibalism and kleptoparasitism (i.e., stealing of prey) are commonplace, and play important regulatory roles in terms of population structure and young-of-year recruitment.

Although most often associated with structurally-complex habitats, this species can utilise a wide range of environments while foraging and is also known to hunt in open water.

Sexual maturity is attained at 1-2 years of age, with females maturing later than males.

The reproductive period extends from February to April, peaking in March. The eggs are released among dense vegetation such as grasses or sedges, with individual females often courted by several males.

This species is threatened by hybridisation with the congeneric Northern Pike (Esox lucius), which has been widely introduced throughout its range. This process was initiated to address the decline in commercially-important native subpopulations, and largely occurred before the Cisalpine Pike was recognised as a distinct taxon.

The introduction of other non-native fish species, particularly Largemouth Bass (Micropterus salmoides), Wels Catfish (Silurus glanis) and Goldfish (Carassius auratus) has also been linked with Cisalpine Pike declines due to increased predation, resource competition or habitat degradation, e.g., increased turbidity or macrophyte loss (see below).

The depletion of marginal, temporarily-inundated wetlands, e.g., reedbeds in Lake Trasimeno, has in some cases severely reduced the extent of suitable spawning and nursery habitats.

Increased eutrophication and turbidity driven by pollution from agricultural, domestic and industrial sources negatively affect feeding and reduce the growth of macrophytes which provide cover for Cisalpine Pike and their prey.

In northern Italy, the ongoing expansion of the piscivorous Great Cormorant (Phalacrocorax carbo) is believed to represent a growing threat, particularly when their numbers increase during winter.

This species is exploited as a game fish. Recreational fishing for trophy-sized pikes has increased notably since the mid-20^th century, and it is now a lucrative industry with a growing international market for specialised pike fishing gear, lures, and other equipment.

It is also harvested commercially in some parts of its range, although such activity is largely confined to lakes. In Lake Trasimeno, it was formerly among the most important commercial species, but landings declined significantly following the introduction of non-native fish species.

This species occurs within the boundaries of numerous protected areas, some of which are listed in the European Union's Natura 2000 network. It is assessed as Endangered for the 2022 iteration of the Red List of Italian Vertebrates, and Data Deficient for the 2022 Swiss National Red List.

In the Lake Trasimeno basin, both commercial and recreational fishing for Cisalpine Pike have been prohibited since 2011. The Trasimeno Ichthyogenic Centre has carried out captive breeding and restocking efforts since 1970. The latter project currently involves the artificial spawning of c. 600 adult individuals and the release of thousands of juveniles annually.

A number of conservation measures have been proposed, mostly focussing on preserving the remaining native subpopulations via a genetic-screening process to map their distribution and identify conservation priorities, plus a review of fisheries regulations to prevent further stocking of hybrid and non-native pikes.

It has been suggested that artificial gravel pit ponds may provide important refuge habitat in some parts of the Cisalpine Pike's range, e.g., the Piedmont region, provided stocking with Northern Pike or hybrid lineages can be prevented.

The ongoing doubt regarding this species' taxonomy (see 'Taxonomic Notes') should ideally be resolved prior to the design of any overarching conservation management plan.