Iberian small-head barbel  (Luciobarbus microcephalus)

The Iberian small-head barbel is classified as Vulnerable (VU) on the IUCN Red List (1).

Although similar to most other Iberian barbels in overall size (2) (3), the Iberian small-head barbel (Luciobarbus microcephalus) is distinguished by its proportionately small head in relation to the body (2). The upperparts of this fish are variable in colour, but are usually brown to olive-brown with yellowish or golden tones, or sometimes completely silver. The underparts are paler. Smaller individuals, below about 15 centimetres in length, are mottled on the back and sides (2).

The Iberian small-head barbel has a relatively large dorsal fin, with a somewhat concave back edge. The last simple (unbranched) ray of this fin is thick and bony, and is strongly serrated along most of its length (2) (3). The female Iberian small-head barbel generally reaches a larger size than the male, and also has a proportionately larger anal fin, which is probably used to dig a hollow in the substrate during egg-laying. Males can also be distinguished by the presence of small projections, known as nuptial tubercles, which appear on the front part of the head during the breeding season (2) (3).

Like other barbel species, the Iberian small-head barbel has four fleshy barbels around the mouth (4), which in this species are quite thin and short in relation to the head (2) (3). The Iberian small-head barbel has thin lips, which are somewhat retracted, not covering the tip of the jaw (2) (3) (5). It can sometimes be difficult to identify Luciobarbus species due to some individuals appearing intermediate in form, possibly as a result of hybridisation between different species (2) (6).

The Iberian small-head barbel is endemic to the Iberian Peninsula, occuring in the Guadiana river basin of Spain and Portugal (1) (2) (3) (5) (6). It also occurs in a small part of the Tajo River, where it may have been introduced (1) (2) (3).

The Iberian small-head barbel inhabits the middle and lower reaches of rivers, where it prefers deep, slow-moving water (1) (2) (3) (5) (6). It has also been recorded in reservoirs (1) (2) (3) (6).

The diet of the Iberian small-head barbel varies seasonally, but consists mainly of invertebrates and their larvae, detritus, sediments and plant material, particularly algae (2) (5) (7). As an individual grows, the proportion of plant material and sediment in its diet increases (2) (7). Like other members of the Cyprinidae family, the Iberian small-head barbel lacks teeth in the jaws, but has a specialised pair of enlarged bones in the throat that possess ‘pharyngeal teeth’, used to process food (4).

Very little is known about the reproductive behaviour of the Iberian small-head barbel. However, it has been recorded spawning between April and June (2) (3), after migrating upriver to shallower, faster-flowing waters (2). During these migrations, the adult barbels may move through very shallow water or even leap over obstacles in their path. After spawning, the adults return to deeper waters (2). The Iberian small-head barbel has been recorded living to at least eight years old (2) (7).

The Iberian small-head barbel is declining due to a combination of habitat loss, habitat alteration and the introduction of non-native fish species. Water extraction and infrastructure such as dams have affected the natural flow regimes of rivers, while the extraction of aggregates such as gravel and sand has affected this species’ spawning grounds. Pollution has also affected water quality (1) (2) (3) (5) (6).

Introduced, non-native fish species such as the pumpkinseed (Lepomis gibbosus), black bullhead (Ameiurus melas), largemouth bass (Micropterus salmoides) and pike (Esox lucius) present a threat to many endemic fish in the region, through predation, competition or the spread of disease (1) (2) (3) (6). The Iberian small-head barbel is also sometimes illegally poached in its spawning grounds, where the shallower water leaves the adults more exposed (2).

In addition to being listed on Annex III of the Bern Convention (8) and Annex V of the European Union Habitats Directive (9), the Iberian small-head barbel is listed as Near Threatened on the Portuguese Red Book (6) and as Rare on the Spanish Red Book (3).

There are no specific conservation measures currently known to be targeted at this fish (2) (3), but a range of actions have been recommended. For example, the Iberian small-head barbel would benefit from better protection of its habitat, including improvements in water quality, controlling water extraction, and assessing the impacts of infrastructure such as dams. Non-native species need to be controlled and any further introductions prevented (2) (3) (6). The Iberian small-head barbel would also benefit from population monitoring and further research into its biology and ecology (2) (6).

Find out more about the Iberian small-head barbel and its conservation:

• FishBase - Luciobarbus microcephalus:
  http://www.fishbase.org/summary/speciessummary.php?id=9592
• Atlas y Libro Rojo de los Peces Continentales de España - Barbus microcephalus:
  http://www.marm.es/imagenes/es/09047122800af657_tcm7-22083.pdf (In Spanish)
• Livro Vermelho dos Vertebrados de Portugal - Barbus microcephalus:
  http://portal.icnb.pt/NR/rdonlyres/CB478D55-FC7C-4EE2-AEFC-84B423307566/3097/LVVP_Peixes_Barbusmicrocephalus.pdf (In Portuguese)
• Enciclopedia Virtual de los Vertebrados Españoles: Barbo cabecicorto - Luciobarbus microcephalus:
  http://www.vertebradosibericos.org/peces/pdf/lucmic.pdf (In Spanish)