South-west European nase (Parachondrostoma toxostoma)

Synonyms:	Chondrostoma toxostoma

Kingdom	Animalia
Phylum	Chordata
Class	Actinopterygii
Order	Cypriniformes
Family	Cyprinidae
Genus	Parachondrostoma (1)
Size	Length: up to 30 cm (2)
Weight	50 - 350 g (3)

The South-west European nase is classified as Vulnerable (VU) on the IUCN Red List (1).

The South-west European nase (Parachondrostoma toxostoma) is a slender-bodied fish, with a short snout and a somewhat conical head (3). The arched, horseshoe-shaped mouth has a thin, horny layer on the lip and a small row of teeth, making it well adapted for scraping algae from the surface of stones (3) (4) (5).

Generally olive green with silvery flanks, the South-west European nase develops a dark band along the sides during spawning. The dorsal and caudal fins are grey, while the pectoral, pelvic and anal fins are typically yellowish (3).

The South-west European nase occurs in the Rhône river basin in France and Switzerland. It also inhabits several coastal rivers in France, and it has been introduced in river basins on the Atlantic coast of France (1) (4) (5).

A freshwater species, the South-west European nase preferentially inhabits the lower reaches of small rivers, where there is clear water and gravelly substrate (1) (2) (3). However, the South-west European nase is often restricted to upstream habitats by competition with the introduced species Chondrostoma nasus (1).

The South-west European nase may also be found in reservoirs (1).

The South-west European nase breeds from March to June (2) (3), with this species moving into smaller tributaries to spawn (3) (6). The eggs are laid in a carefully selected spawning site, which is typically a boulder in a deep pool, downstream of riffles, where the water contains more oxygen and the temperature remains constant (6).

During the larval period, the South-west European nase feeds on plankton, gathering in small shoals at the surface of pools (6). The adult South-west European nase feeds by scraping and ‘pecking’ at algae and small aquatic invertebrates on rocks and pebbles. It will also feed on plants and, occasionally, other small fish (2) (3).

The South-west European nase is threatened by pollution, water extraction and the creation of dams which destroy this species’ habitat. It is also threatened by the introduction of Chondrostoma nasus, which competes with the South-west European nase for space and resources, including spawning sites (1) (3).

The South-west European nase is listed on Annex II of the European Union Habitats Directive (7) and on Appendix III of the Bern Convention, which aims to conserve wild flora and fauna and their natural habitats (1) (8).

Recommended conservation measures for the South-west European nase include maintaining the quality of its river habitat, as well as limiting water extraction and dam construction in areas of vital habitat. Fishing of this species should also be monitored and regulated to ensure that there are no negative impacts on the population (3).  

• FishBase - South-west European nase:
  http://www.fishbase.gr/summary/speciessummary.php?id=4477

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

• Algae: simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.
• Anal fin: in fish, an unpaired fin on the under surface of a fish, behind the anus.
• Caudal fin: the tail fin of a fish.
• Dorsal fin: the unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.
• Invertebrates: animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones), echinoderms, and others.
• Larval: of the stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
• Pectoral fins: in fish, the pair of fins that are found one on each side of the body just behind the gills. They are generally used for balancing and braking.
• Pelvic fins: in fish, the pair of fins found on the underside of the body.
• Plankton: aquatic organisms, usually tiny, that drift passively with water movements; may be phytoplankton (plants), zooplankton (animals), or other organisms such as bacteria.
• Riffles: light rapids where water flows across a shallow section of river.
• Spawning: the production or depositing of large quantities of eggs in water.

1. IUCN Red List (May, 2011)
   http://www.iucnredlist.org/
2. FishBase - South-west European nase (May, 2011)
   http://www.fishbase.gr/summary/speciessummary.php?id=4477
3. Bensetti, F. and Gaudillat, V. (MNHN-SPN) (Coord). (2002) Cahiers d'habitats - Natura 2000. Connaissance et gestion des habitats et des espèces d'intérêt communautaire. Tome 7 - Espèces Animales. La Documentation Française, Paris. Available at:
   http://inpn.mnhn.fr/docs/cahab/tome7.pdf
4. Elvira, B. (1987) Taxonomic revision of the genus Chondrostoma Agazziz, 1835 (Pisces, Cyprinidae). Cybium, 11(2): 111-140.
5. Changeux, T. and Pont, D. (1995) Current status of the riverine fishes of the French Mediterranean Basin. Biological Conservation, 72: 137-158.
6. Gozlana, R.E., Coppa, G.H. and Tourenq, J-N. (1999) Early development of the sofie, Chondrostoma toxostoma. Environmental Biology of Fishes, 56: 67-77.
7. EC Habitats Directive (May, 2011)
   http://www.jncc.gov.uk/page-1374
8. Council of Europe: Bern Convention (May, 2011)
   http://conventions.coe.int/Treaty/EN/Treaties/Html/104.htm