Northern straight-mouth nase  (Pseudochondrostoma duriense)

The northern straight-mouth nase is classified as Vulnerable (VU) on the IUCN Red List (1).

The northern straight-mouth nase (Pseudochondrostoma duriense) is a medium-sized (3) member of the Cyprinidae family, a diverse group of fish comprising over 2,000 species (4). Fish in this family have the ability to protrude the upper jaw, while this species’ lower jaw is slightly arched (2). As its common name suggests, the mouth of the northern straight mouth nase is characteristically straight (3).

Populations of northern straight-mouth nase in Portugal and Galacia, Spain usually have small scales, and are covered with numerous black spots on the upperparts (2) (3). The body of the northern straight-mouth nase is more elongated than other cyprinids, with large dorsal and anal fins (3).

Most cyprinids do not display any visible differences between the male and female (4), although males of this species develop numerous small tubercules over the whole body during breeding season (3).

The northern straight-mouth nase is endemic to Spain and Portugal (1) (6).

The northern straight-mouth nase inhabits freshwater rivers with strong currents (1), where it is generally found swimming close to the riverbed (2). It also occurs in reservoirs (3).

An omnivorous species, the northern straight-mouth nase feeds on detritus and plant material on the stone-filled river bed (5) (7). This is supplemented with aquatic invertebrates which drift in the water column throughout the daytime feeding hours (2) (5). Cyprinid species are toothless, instead having a pair of bones inside the throat which grind against each other to aid the digestion process (4).

The spawning season of the northern straight-mouth nase takes place from April to June, after the upstream migration which occurs prior to spawning (2) (7). The eggs of Cyprinids are around one millimetre in diameter and development is fast, with newly hatched larvae immediately searching for small crustaceans and other small prey to eat (8).

The northern straight-mouth nase can be found in groups, especially around the time of the migration prior to spawning (2).

Throughout the range of the northern straight-mouth nase, canals and dams have been constructed, with plans to construct more, leading to the destruction of this species’ habitat (1). Water extraction and the addition of agricultural and industrial waste into the water are also threatening the nase and its habitat (3). The introduction of non-native species is another potential threat to the northern straight-mouth nase (1), with introduced species such as Lepomis gibbosus, Micropterus salnmoides, Esox lucius, Sander lucioperca,as well as other cyprinids competing with the northern straight-mouth nase for food and resources (3).

The northern straight-mouth nase is listed on Annex II of the EU Habitats Directive, which protects over 1,000 animals and 200 habitat types within Europe (9). It is also listed on Annex III of the Bern Convention, which aims to conserve wild flora and fauna and their natural habitats in Europe (1) (10). Controlling and treating the waste which is added to the water bodies could be an effective method of conserving the habitat of this species, while reduction of irrigation when water levels are low and controlling the introduction of non-native species would also benefit the northern straight-mouth nase (3).

Find out more about the northern straight-mouth nase:

• FishBase - Pseudochondrostoma duriense:
  http://www.fishbase.org/summary/Pseudochondrostoma-duriense.html