Iberian nase, a freshwater fish

Also known as river-nase or straight-mouth nase, the Iberian nase can be spotted all year round in streams and even in Portuguese dams. It can be found also in areas with abundant riparian vegetation, such as Barroca da Serra – Penamacor, currently under The Navigator Company management.

The Iberian nase holds the “Least concern (LC)” conservation status and is considered a very common freshwater fish in Portugal, perhaps given its status of both endemic and resident species of the Iberian Peninsula. Oddly enough its scientific name Pseudochondrostoma polylepis is longer than its common name, probably thanks to its elongated body, longer than that of its cyprinid relatives. Medium-sized, it has a prominent muzzle, an intricate mouth and fins with a silver tint. In turn, scales are small and its average weight does not exceed 400 to 500 grams.

Habitat: adapts easily to different types of water systems and can be found in cold and well-oxygenated waters, although it occurs mostly in small watercourses with moderate to strong currents. It can also occur in the reservoirs of Portuguese dams, where it is seen quite frequently.

Food: This species feeds on larvae of insects and small invertebrates (particularly molluscs), but also on vegetation (algae) that adhere to the bottom and the gravel. It uses the cutting plate on its lower lip to be able to tear.

Reproduction: spawning occurs upstream in shallow running water courses during the Spring, more specifically between March and June. At the bottom of the river, females lay the eggs on a gravel substrate, which then adhere to the stones or algae.

Threats to this species: despite its least concern status, conservation of freshwater fish in Portugal is threatened by several factors with a cumulative effect on watercourses. This is the case of pollution, habitat destruction, water scarcity, loss of connectivity due to the construction of insurmountable barriers (examples: dams and dams) and also the proliferation of invasive species, particularly animals such as the Northern pike (Esox lucius), pumpkinseed (Lepomis gibbosus) and largemouth bass (Micropterus salmoides), which compete or prey on the Iberian nase.