Allis Shad

• Its Critically Endangered category is recent: the IUCN assigned it in 2024, after estimating a global decline of around 80% in twenty years.
• Its historical range ran from Norway to Morocco. Today relict populations remain in a few large rivers of France (Loire, Garonne-Dordogne, Adour) and Portugal.
• The collapse of the Gironde population is a case study: fishing mortality in the estuary triggered an Allee effect, meaning the population became so sparse that it could no longer recover on its own even once the pressure was removed.
• Dams are its other great problem, because they cut off its access to the headwater spawning grounds; it is the same mechanism that brought down the beluga sturgeon.
• It is told apart from the herring by a dark spot behind the gill cover, sometimes followed by a row of up to six more spots.
• In Ireland four special areas of conservation have been designated on stretches where the shad are known to spawn.

Skeleton type

Vertebrate - internal bony skeleton (bony fish)

Habitat and environment

Anadromous: it lives in the north-east Atlantic, the western Baltic and the western Mediterranean and ascends rivers to spawn

Sexual maturity

4.5 years

Sources consulted: Wikipedia (es): Alosa alosa