CR

Unio tumidiformis

DecliningVUEUVUEU

Overview

A detailed profile for this species is sourced from the IUCN Red List of Threatened Species as assessments become available.

Unio tumidiformis faces severe population decline primarily due to water pollution from agricultural runoff and industrial discharge, which degrades water quality in its freshwater habitats. Dam construction and river channelization have fragmented populations and altered natural flow regimes essential for reproduction. The species is also threatened by invasive zebra mussels that compete for resources and attach to native shells, potentially suffocating individuals.

Threat summary

Habitat

This freshwater mussel inhabits clean, well-oxygenated rivers and streams with sandy or gravelly substrates. It requires stable water flow and good water quality to filter-feed on plankton and organic particles.

Wetlands (inland)· major

Conservation measures underway

Habitat & natural process restorationSpecies managementSpecies recovery

Other threatened species in UNIONIDAE

VU

Brazzaea anceyi

Unknown
EN

Potomida littoralis

Declining
EN

Potomida acarnanica

Declining
CR

Physunio ferrugineus

Unknown

Threatened in Portugal

VU

Lepiota echinella

Unknown
VU

Helictochloa hackelii

Declining
EN

Double Spleenwort

Asplenium anceps

Declining
VU

Madeira Rustyback Fern

Asplenium lolegnamense

Declining

Frequently asked questions

Why is Unio tumidiformis classified as Critically Endangered?
Unio tumidiformis is classified as Critically Endangered — facing an extremely high risk of extinction in the wild — because population sizes are very small, declining sharply, or restricted to a tiny range. Unio tumidiformis faces severe population decline primarily due to water pollution from agricultural runoff and industrial discharge, which degrades water quality in its freshwater habitats. Dam construction and river channelization have fragmented populations and altered natural flow regimes essential for reproduction. The species is also threatened by invasive zebra mussels that compete for resources and attach to native shells, potentially suffocating individuals.
Where does Unio tumidiformis live?
Unio tumidiformis occurs in Portugal, and Spain. Country-level distribution data is sourced from the IUCN Red List and cross-referenced with GBIF occurrences.
What are the main threats to Unio tumidiformis?
The main threats to Unio tumidiformis are 1.1, 11.1, 2.1, and 7.2. The full IUCN-classified threat record for this species is detailed on the species page.

Get weekly conservation intelligence

One short digest a week of the most striking species and country data we ship, plus breaking conservation news paired with our database where it matters.

Free, no spam. One-click unsubscribe in every email.