Western ruivaco  (Achondrostoma occidentale)

Classified as Endangered (EN) on the IUCN Red List (1).

The western ruivaco (Achondrostoma occidentale) is a small, inconspicuous freshwater fish which is endemic to a small part of western Portugal (1) (3). A glistening, yellow band runs the length of the western ruivaco’s flank and the base of its fins are orange. The colouration on the side of the western ruivaco becomes paler towards the underside (3). This feature is more pronounced in the western ruivaco than in the closely related Chondrostoma arcasii and Chondrostoma oligolepis, which have red rather than orange bases to their fins. These differences help to identify the western ruivaco from other members of the genus. The western ruivaco also has a much thicker jaw bone, a different arrangement and number of scales and a more elongated body than related species (3).

The western ruivaco only occurs in three small coastal streams in western-central Portugal: the Sizandro, Safarujo and Alcabrichel (3) (4).

The western ruivaco lives in small coastal streams upstream of river pollution (4). Due to reduced water flow during the summer, the western ruivaco makes use of small pools and the shade from surrounding vegetation as protection from the summer heat (3) (4).

The western ruivaco reaches sexual maturity at one year old (2) and breeds in temperate waters in late April and May (4). The fish gather in spawning groups and the females release sticky eggs, which attach to stones and vegetation (4).Like other members of its family the western ruivaco is likely to be an opportunistic feeder, which mainly eats aquatic invertebrates (5). 

The western ruivaco is threatened with pollution from industry, agriculture and sewage plants (1), and is now found only in small, isolated areas upstream of major pollution sources (3) (4). Summer droughts and the illegal removal of water for intensive agriculture has reduced the habitat of this threatened fish and had a major impact on its population (2).The surviving populations of the western ruivaco are very small (4), and it is thought that the population in the Safarujo may have been lost after the stream dried up (1).

There are currently no known conservation projects relating to the western ruivaco (1) (4) but there have been pilot captive breeding studies which could be useful if reintroductions become necessary (2). This study took a population of 16 adult western ruivaco from the Alcabrichel River for captive breeding (2) and showedencouraging results. Measures to restore the rivers inhabited by the western ruivaco have also been recommended to protect this highly threatened fish (4).

To find out more about the western ruivaco see:

• Fishbase
  http://www.fishbase.org/