Kodaka / kolaka (Alosa alosa)
Like the Atlantic salmon, the allis shad is a species which is born in rivers, migrates to the sea and returns to river basins to spawn. In adulthood, it can reach up to 4 kg. It enters river areas with slow and relatively deep waters to spawn, after which it either dies or returns to the sea.
The species is usually found in the middle and lower courses of rivers during the breeding season and juvenile phase. The spawning grounds it uses are located in river areas between slow, deep waters and areas with current, always in fresh water and beyond the influence of the tide. The allis shad is very sensitive to moderate obstacles due to its poor or practically null ability to leap.
The only known population in the Basque Country is in the lower course of the River Bidasoa. A sporadic presence of the species has also been registered in the Rivers Urumea and Oria, and it is considered extinct in all the other basins.
It is common to observe allis shad in the Navarrese section of the River Bidasoa in the breeding season up to the Endarlatsa dam, the first obstacle to migration when running up from the sea. Some allis shad manage to overcome this barrier and reach the Las Nazas stretch, but probably not in sufficient number to guarantee spawning. The allis shad is key to the management of the SAC "River Bidasoa" and the demolition of barriers is one of the chief measures proposed in order to improve its conservation status.
Alosa alosa (allis shad)
Annexes to Directive 92/43/CEE: II y V
|Site||Population size||Conservation status|
|SAC River Leitzaran ES2120013||Not present||Not present|
|SAC River Bidasoa ES2200014||B||B|
|SAC River Baztan and Artesiaga Brook ES2200023||Not present||Not present|
|SAC Señorío de Bertiz ES2200017||Ausente / Not present||Ausente / Not present|
|SCI Artikutza ES2200010||Not present||Not present|
|SCI Belate ES2200018||Not present||Not present|
A: Excellent representation B: Good representation C: Significant representation. D: Insignificant representation
Basque Country Nature information system - Allis shad
National inventories - Alosa alosa (Ministry of Agriculture, Food and the Environment)
SIBIC 2014. Spanish Fish Chart. Electronic publication (version 01/2015).