Esox lucius

The European pike (Esox lucius) is a species of esociform actinopterygian of the freshwater family Esocids.

Description

The European pike has a long body, almost cylindrical in shape. The relatively long head has a duckbill-shaped mouth that opens upwards. The relatively long dorsal fin extends backwards.

The color varies with the habitat, the back is normally green-brown, the coloration changes to lighter tones approaching the white belly. The jaws are provided with specialized teeth, as are the tongue and gill arches. The pike has between 110 and 130 small scales along the lateral line.

The average size is between about 50 cm and 1 meter. There are specimens up to a meter and a half and weights of up to 25 kg. The maximum size mentioned above is normally only reached by the female, the male does not reach more than 90 cm.

Habitat and situation in Spain

E. lucius caught with hook in the River Dráva, Hungary.

Pike are a firm habitat fish that like to stay close to shore in running waters, lakes, and large ponds. It prefers shabby shores and other hiding possibilities, such as logs, roots, rocks, bridges, vegetation. It needs good water quality to thrive, as well as fresh water, stable water levels, abundance of grass fish, and abundance of vegetation.

It is found in most of the Iberian Peninsula, except in Galicia, with greater abundance in the Júcar reservoirs, Castilian, Leonese and Extremaduran rivers.Ex: Cíjara swamp.

It was introduced in the 1950s by the Sport Fishing Administration, and has been translocated to many places on the peninsula. It currently constitutes an important threat to the conservation of biodiversity due to its impact on the native ichthyofauna, as well as on amphibians, reptiles linked to aquatic ecosystems and even avifauna.

Invasive character in Spain

Due to its colonizing potential and constituting a serious threat to native species, habitats or ecosystems, this species was introduced into the Spanish Catalog of Invasive Alien Species, approved by Royal Decree 1628/2011, of November 14 (valid until August 4, 2013), repealed by Royal Decree 630/2013, of August 2, which regulates the Spanish Catalog of invasive alien species, their introduction into the natural environment, possession, transport, traffic and trade thanks to a Supreme Court ruling that failed to keep some excluded species in the catalog. Unfortunately, the previous decree came to light but was not applied due to its infeasibility (until its repeal), due to the impossibility of repopulating the waters with autochthonous species, due to the construction of the dams of the reservoirs, which almost always prevent the process of rise and spawning of some of these species.

Behavior

Exemplar of the Vltava exhibition in Prague

Pike feed on fish of all species and crabs; they can eat fry of their own species. Toads, birds, and small mammals also belong to their prey spectrum. Pike have a reputation for being a very aggressive predatory fish, despite spending most of their time hiding in vegetation.

On rare occasions, adults have been found with birds in their digestive system. Heinrich Engler described an extraordinary case in his monograph: a pike only 30 cm long had tried to swallow an adult male of a waterfowl species that was 35 cm long. The two animals, dead, were found at a distance of 20m from the water, the bird with its head and neck inside the pike's mouth. Obviously, the bird had managed to make its way to the mainland before both animals drowned there.^{[citation needed]}

Pike sometimes reach the age of 30 years. Breeding takes place on banks with abundant vegetation.

The jaws of pike are made of cartilage and are different from the bony jaws of most fish. The teeth are replaceable, and are arranged in rows one behind the other, so that when a tooth is lost, a new piece moves forward and replaces it. Pike lose their teeth in two ways: accidentally while eating or through a natural molting process.

Open mouth of a specimen of the Ricobayo reservoir, Zamora.