This taxon was treated as a subpopulation of the European Grayling (Thymallus thymallus) prior to its description (Persat et al. 2019).

The Loire Grayling is endemic to France and has a restricted range (area of occupancy (AOO) c. 600 km²), which meets the threshold for Vulnerable under Criterion B2. It occurs at eight locations where the quality of habitat is estimated to be declining. Therefore, this species is assessed as Vulnerable under Criterion B (B2ab(iii)).

This species is endemic to the upper Loire River system in France.

It has been recorded at eight sites, comprising a stretch of the Loire main stem plus the Besbre, Lignon, Allier, Sioule, Dore, Allagnon and upper Vienne rivers, but may have been more widespread prior to its decline (see 'Population').

A non-native subpopulation became established in the Corrèze River, a tributary within the larger Dordogne River system, after individuals were introduced from a federal fish farm. Additional translocations have reportedly taken place elsewhere.

This species' current population size and trend have not been quantified, but it has declined significantly since the early 20^th century.

It has been extirpated from the Besbre River and the Taurion River, a tributary in the upper Vienne River system, and possibly elsewhere. In addition, it was almost eliminated from the Sioule River but has partially recovered as a result of management actions.

This pattern might be ongoing (see 'Threats'), but there is evidence that abundance is increasing at some locations (see 'Conservation').

This benthic, rheophilic species predominantly inhabits fast-flowing, well-oxygenated and unpolluted middle reaches of rivers and streams which are often referred to as the "grayling zone".

It is sometimes found in smaller rivers with relatively low discharge, but appears to prefer medium to large-sized channels of at least five metres in width flowing through foothill canyons and plateaus. It does not occur in headwaters.

The adult diet largely comprises benthic and drifting invertebrates such as Trichoptera, supplemented by terrestrial insects and smaller fishes.

Adult individuals are territorial and select stream positions in dominance hierarchies based on maximising their energy intake, usually favouring depressions near the centre of the current where they employ a "sit-and-wait" foraging strategy.

Its life history has not been extensively-studied, but it is presumably comparable to that of the European Grayling (Thymallus thymallus). The annual reproductive period is thus likely to extend from spring to early summer, at which point sexually mature adults migrate short distances to their favoured spawning sites.

Grayling typically spawn in flowing shallows with well-washed substrata of fine gravel, sometimes mixed with small cobbles or sand´. Spawning most often occurs during the later hours of the day, when water temperatures are at their peak.

Sexually active male individuals arrive at spawning sites prior to females and aggressively defend territories which may measure several square metres in size. Visual barriers such as boulders or woody structures often play a role in reducing territory size and aggressive encounters between rival males. Females remain in deeper pools and only enter male territories for short periods to spawn. Both males and females may spawn on multiple occasions with different partners during a single season, and some non-territorial males may exhibit sneaking behaviour.

The eggs remain in the substrate for 2-4 weeks before hatching. The emergent larvae spend a further 4-10 days within the substrate until their yolk sacs are absorbed, then spend a number of weeks foraging in marginal zones with low flow and abundant cover. They later occupy the upper third of the water column close to stream banks, where they prey on drifting and terrestrial invertebrates until reaching a size of 25-28 millimetres, when they move into benthic habitats.

Although European Grayling eggs and fry of unknown origin have been imported and stocked within this species' range since the mid-20^th century (see 'Conservation') there is to date no evidence of hybridisation or introgression, indicating that the long-term survival of stocked individuals has been low to non-existent. This suggests that native individuals possess a competitive advantage over translocated stocks which may be related to local environmental conditions, demographic structure or reproductive isolation.

This species' decline has primarily been driven by river regulation and other forms of habitat degradation, which have resulted in widespread loss of the heterogeneous, interconnected fluvial habitats required to complete its life-cycle.

In particular, the construction of dams, weirs and other barriers has altered natural flow and sedimentation regimes, blocked access to spawning and seasonal foraging sites, fragmented subpopulations, interfered with the distinctive habitat shifts required during early ontogenetic development, and generally reduced the extent of suitable habitat for all life stages. The quality of available habitat has been further diminished by bank stabilisation, channelisation and other efforts to enhance flood protection or river transportation links.

Hydroelectric dams have created regular fluctuations in discharge and water temperature (hydropeaking and thermopeaking) which cause dewatering of spawning sites and loss of stable nursery habitat for juveniles, plus downstream displacement and stranding of individual fish.

Furthermore, the combined effect of hydropeaking, dam flushing operations, changes in land use, and the removal of riparian vegetation has increased accumulation of fine sediments at spawning sites, impairing the hatching and survival rates of eggs and larvae.

The industrial extraction of riverine gravel and other sediments for urban development has further reduced the extent of available spawning sites.

This species is also likely to have declined due to widespread agricultural, domestic and industrial pollution during the 20^th century, some of which persists today.

Predation pressure from increasingly abundant piscivorous birds, particularly Great Cormorant (Phalacrocorax carbo), is believed to represent a significant threat at some locations.

Although there is currently no evidence that introgressive hybridisation with stocked individuals of non-native origin represents a threat (see 'Habitat and Ecology'), stocking may nevertheless impair natural recruitment and fitness through increased resource competition, introduction of parasites and pathogens, and by favouring the local abundance of predators.

The extent of habitat is likely to be impacted by climate change, due to increased water temperatures and diminishing river discharge.

This species is a popular game fish that is particularly targeted by fly-anglers and recreational fisheries, and stocking efforts have been established in collaboration with local angling associations.

The latter groups continue to manage local stocks, and predominantly operate a catch-and-release policy.

This species is included (as Thymallus thymallus) in Appendix III of the Bern Convention and Annex V of the European Union Habitats Directive.

It occurs within the boundaries of several protected areas, some of which are included in the European Union's Natura 2000 network (e.g., sites FR8201758, FR8212024, FR8301074, FR8312002, FR8312009).

Efforts to supplement declining abundance based on stocking and supportive rearing have been ongoing throughout much of its range since the 1960s, and have in most cases involved the use of domesticated and/or non-native individuals obtained from a range of unconfirmed sources. The practice apparently continues, despite evidence that the survival of the stocked individuals is extremely low at best (see 'Habitats and Ecology').

The inference from research is that a well-structured native subpopulation is able to impede the establishment of non-native grayling lineages, implying that supplemental stocking at locations where habitat quality remains suitable for natural recruitment does not represent an efficient management routine.

Proposed alternatives include investment in improving habitat connectivity and quality through the removal of barriers, installation of fishways, restoration of heterogeneous natural features, increased residual flows in regulated river stretches, reduced hydropeaking and improved control of reservoir flushing operations.

Some preliminary barrier removal and habitat restoration efforts have taken place, and the results are reportedly encouraging. It may also have benefitted from measures to improve fluvial ecosystems within the framework of the European Union's Water Framework Directive 2000/60/EC.

Angling restrictions comprise annual closed seasons and minimum catch size limits in addition to no-kill policies, e.g., in the Allier River and its tributaries.

A deeper understanding of this species' current abundance, population trend and life history would likely prove useful in the development of future management actions.