The Iberian Peninsula: a European hotspot for freshwater diversity and curiosity

Achondrostoma: four tiny, beautiful fish species endemic to Iberia. Image: Ana Maria Geraldes

This month’s guest curator is Dr Ana Maria Geraldes from the Instituto Politécnico de Bragança in Portugal, who supplied the information about an incredible range of freshwater species found in the Iberian Peninsula (Spain, Portugal, Andorra and Gibraltar).

The Iberian Peninsula. Image: Wikipedia

The Iberian Peninsula is a hotspot for freshwater fish biodiversity and curiosity in Europe. The existence of geographical barriers such as the Atlantic Ocean, Mediterranean Sea and Pyrenees Mountains prevents fish from moving to other regions, creating a variety of different, isolated habitats, each subject to a wide range in climate.  This peculiar combination of factors has combined to produce a high number of endemic species through evolution.

What are ‘endemic species’?

Endemism is the word used to describe species that are only found in a very small habitat and nowhere else.  For example, the Galapagos tortoise is endemic to the Galapagos islands, because it is only found there (except in zoos, which don’t necessarily count as “native” habitats!).  Species become endemic to a small area because of geographical isolation, causing them to evolve in different ways to similar species found in other habitats (see for example, the differences between the Galapagos tortoise, and other tortoises found elsewhere).

Endemic fish species on the Iberian Peninsula: a hotbed of diversity and curiosity

The Iberian peninsula is home to 36 endemic species of cyprinids: tiny, shimmering and beautiful fish. Some are restricted to very small areas, such as the Southwestern arched-mouth nase (only named in 2005!), Portuguese arched-mouth nase, Western ruivaco, Squalius aradensis and Squalius torgalensis….not all of these fish are well-known enough to have been named yet!).

Iberian Small Headed Barbel (Image:

Another curiosity is the Iberian barbel.  In Iberia nine barbel species can be found. Eight of them are endemic to the region!  This picture shows an Iberian small-headed barbel leaping up a waterfall.

The tiny jarabugo, one of the rarest fish in the world and it's distribution in Iberia. Image: Wikipedia

Rio Guadiana, home to the jarabugo. Image: Wikipedia

One of the most endangered fish in the world calls the Iberian peninsula its home.  The jarabugo (Anaecypris hispanica) lives in River Guadiana catchment, a tiny, shimmering silver fish with an upturned mouth and large eyes.

The Iberian Peninsula: endemic species under threat?

The majority of these species are well adapted to the seasonal changes in river flow, especially during the droughts that often occur in Iberian streams. Despite their resilience many of these species are threatened. The presence of dams and weirs is considered to be one of the main factors that are negatively affecting Iberian freshwater fish. In Portugal, rivers are impounded by almost 200 large dams and more than 3000 small weirs and the construction of more eleven large dams are planned. The scenario is similar in Spain. River impoundment causes a loss of suitable habitats for these species, including the destruction of spawning areas.  Besides, the loss of river connectivity contribute to genetic erosion – the process where the gene pool of an endangered population is gradually decreased, restricting future reproduction and threatening the survival of the species.

It is true that some of resident species such as Barbus spp. and Pseudochondrostoma spp. can also occur in dam reservoirs. However, the long term survival of these species is not guaranteed because the loss of river connectivity caused by dams prevents their migratory movements to upstream tributaries. Besides, even though reproduction is possible the increased water level fluctuations occurring in reservoirs will jeopardize fish reproductive success. Other possible threats include water pollution, eutrophication, water transfer projects and species translocations between different catchments and non-native species introductions.

A large dam is being built on the Sabor River (NE Portugal). Because of its natural heritage together with Maçãs River valley were included in Natura 2000 Network (PTZEP0037/PTCON0021). Sabor was considered one of the last wild Portuguese rivers because of the absence of large dams. After a long and extremely controversial process the building has started and the dam will be finished by 2013. A fine spawning area for Luciobarbus bocagei is likely to be lost forever.

The black bass. A non-native, predatory fish which may threaten the endemic fish of the Iberian Peninsula. Image: Ana Maria Geraldes

Finally, the introduction of non-native carnivorous species such as pike (Esox lucius) and black bass (Micropterus salmoides) also has the potential to threaten Iberian fish.

The Iberian Peninsula: a hotspot of diversity and curiosity

We’ve encountered some incredible, rare and beautiful species this month, thanks to the fascinating information provided by our guest curators.  The cocktail of geographical factors – mountains, oceans and climate – in the Iberian Peninsula has driven a fascinating range of fish evolution pathways, resulting in the diverse range of endemic species we see today.  If you’d like more information, please see the links below, and please feel free to submit your suggestions as a ‘guest curator’ for future entries into the Cabinet of Freshwater Curiosities!

For more information….

Guest curator: A.M. Geraldes & A. Teixeira

CIMO, Escola Superior Agrária Instituto Politécnico de Bragança
Apartado 172 5301-854 Bragança

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