This was considered by Haas (1969) to be a subspecies of Unio pictorum, and was subsequently considered within the synonymy of Unio pictorum. However, based on an integrative systematics approach, Khalloufi et al. (2011) redescribed Unio ravoisieri as a valid species separate from Unio pictorum.

European regional assessment: Critically Endangered (CR)
EU 27 regional assessment: Critically Endangered (CR)

The species is assessed as Critically Endangered CR B1ab(iii,v) for Europe and the EU27 Member States based on a restricted distribution of only 12 km² in extent of occurrence. It is also severely fragmented and experiencing a continuous decline in the number of mature individuals and quality of habitat.

The species is probably one of the most threatened Unionoid bivalves in Europe due to its restricted range (only two subpopulations) and very low densities. Although the species seems to be widespread in Algeria and Tunisia, the presence of dams and decreasing water quality and quantity in these countries is a major threat to its entire African range.

Due to the isolation of the European populations from North Africa and the thousands of physical barriers (e.g. dams and weirs) in most hydrographic basins of both continents, the transcontinental migration of larvae or fish infested with U. ravoisieri larvae should be minimal or non-existent.

Within the European region, this species is restricted to two locations in northeastern Spain (Lake Banyoles, from where it was observed in 2012, and the River Ser, both in the province of Girona, Catalonia) (Araujo et al. 2009). Attempts to reintroduce the mussel and its fish host have had limited success. The species used to have a wider distribution in other rivers in Catalonia (Araujo et al. 2009).

Out of the European region, the species has a disjunct distribution in rivers of Algeria and Tunisia (Khalloufi et al. 2011).

In Spain, the species has a very restricted range, with only two known subpopulations of very low abundances, one in the River Ser and the other in Lake Banyoles, belonging to two small Mediterranean basins in northern Catalonia (Khalloufi et al. 2011). The number of individuals is gradually decreasing (Araujo et al. 2009), despite the reintroduction of specimens that significantly increased the population in Lake Banyoles, but no recent monitoring results have been published.

The total population size is not estimated; while only about 100 individuals occur in the lake, the species is much more abundant in the river.

Unio ravoisieri has the typical unique reproductive traits of most Unionidae species, including larval parental care (i.e., brooding) and larval parasitism on freshwater fishes (and occasionally other vertebrates) (Lopes-Lima et al. 2017). The larvae (glochidia) are triangular and hooked with a length of ∼210 μm (Khalloufi et al. 2011). Females are gravid from April to July and larvae (glochidia) are released from May to July. Two native cyprinid species, Barbus meridionalis and Squalius laietanus, and the blenniid Salaria fluviatilis are known to be host fish for successful larval metamorphosis (Araujo et al. 2015).

In the River Ser (Fluvia basin), specimens live burrowed in the banks, usually in the shade of trees and among submerged roots. In Lake Banyoles (Ter basin) they are buried in the substrate from the shore to a depth of 10 m (Araujo et al. 2009).

Both subpopulations in Spain are small and of low abundance (Araujo et al. 2009). Lake Banyoles has been subject to several introductions of non-native fish species, five of which dominate the fish community (in order of importance: Scardinius erythrophthalmus, Cyprinus carpio, Micropterus salmoides, Lepomis gibbosus, Perca fluviatilis). These alien fishes have almost eliminated and replaced the natural host fishes of U. ravoisieri. This has had a severe impact on the U. ravoisieri population, which has experienced a sharp decline, with only around 100 individuals (native and reintroduced) remaining in the lake (Araujo et al. 2015).

Freshwater habitats in Catalonia are threatened by poor river management, intensive agriculture, urbanisation and pollution. The over-extraction of water for agricultural and urban purposes is also one of the main threats to all freshwater species, including Unio ravoisieri (Araujo et al. 2009). Climate change predictions of global warming and increased draughts are likely to exacerbate water shortages in smaller rivers and streams in the near future.

No use or trade are known for this species.

In Europe, the species is protected (as Unio elongatulus) under Annex III of the Bern Convention on the Conservation of European Wildlife and Natural Habitats. It is also listed in Annex V of the Habitats Directive as a species of Community interest whose taking and exploitation in the wild may be subject to management measures. It is also listed as Endangered and strictly protected in the Spanish Catalog of Endangered Species. Lake Banyoles is a Natura 2000 site and a Ramsar site.

A recent LIFE project (LIFE 08 NAT/E/000078 "Estany Project") dedicated to the restoration of the native aquatic fauna of Lake Banyoles in Spain included an ex situ breeding programme for Unio ravoisieri and several (224) individuals were introduced into the lake, but the impact of this action is not yet known.

Conservation measures are urgently needed to restore freshwater habitats, maintain ecological flows and control exotic species. Ongoing captive breeding programmes for U. ravoisieri and its fish hosts are also needed over the coming decades to augment and propagate the species in rehabilitated habitats. Further research into the population and its habitat would be beneficial.