Global and European regional assessment: Near Threatened (NT)
EU 27 regional assessment: Vulnerable (VU°)

The Skadar Bleak does not approach the range thresholds for Vulnerable under Criterion B1 (extent of occurrence (EOO) < 20,000 km²) or D2, and Criterion B2 is precluded by its uncertain area of occupancy (AOO). The population size is believed to exceed 10,000 mature individuals, and does not approach the thresholds for Criteria C or D. There exists no quantitative analysis which would permit application of Criterion E.

Although no explicit population trend data exists, it is possible that a suspected ongoing reduction based on field observations, fisheries data and declining habitat quality may approach or meet the threshold for Vulnerable under Criterion A2 (≥ 30% over the past 15 years = three generations). As a result of this data uncertainty, Least Concern and Vulnerable are equally plausible Red List categories for the present assessment, and this species is assessed as Near Threatened at the global and European regional scales.

In the EU 27 member states, the EOO is c. 2,813 km², which meets the threshold for Endangered under Criterion B1 (EOO < 5,000 km²), and it is present at 1-3 locations where the extent and quality of habitat are estimated to be declining. However, the single identified subpopulation comprises part of a larger subpopulation occupying a transboundary river system, hence its assessment is downlisted by one category from Endangered to Vulnerable under Criterion B (B1ab(iii)).

This species is endemic to the Western Balkans region, where its range extends from the Bojana (sq. Bunë) River in Montenegro and northern Albania to the Vjosa (el. Αώος/Aoös) River in southern Albania and Greece, including the Skadar (sq. Liqeni i Shkodrës; cnr. Skadarsko jezero) and Ohrid (sq. Liqeni i Ohrit; mk. Охридско Езеро) lake basins. It is absent from the upper reaches of rivers draining to Lake Skadar, including the isolated Nikšić polje in the upper Zeta River catchment.

An introduced subpopulation is established in the semi-artificial Vlasina reservoir in the Danube River system, southeastern Serbia.

This species' population size is unknown, but is understood to exceed the minimum threshold for Red List criteria (< 10,000 mature individuals). The current population trend has not been quantified, and the number of subpopulations is unclear.

Abundance is suspected to be declining in some parts of its range, e.g., Lake Skadar and some Albanian rivers, based on field observations, fisheries data and declining habitat quality (see 'Threats').

In the EU 27 member states a single subpopulation is present in the Vjosa River system, but it is part of a significantly larger subpopulation that includes downstream reaches in Albania.

This gregarious species inhabits low-gradient river channels and fluvial lakes. In particular, the Drin (sq. Drini; mk. Дрим) River system is a major biodiversity hotspot, within which the oligotrophic and oligomictic lakes Ohrid and Skadar hold the largest individual stocks and are particularly significant in terms of endemic aquatic fauna.

Lake Ohrid is of tectonic origin and is considered to be the oldest extant lake in Europe with an age of c. 2-3 million years. Its surface area is c. 358 km² and it has a maximum depth of c. 289 metres (average depth c. 164 metres). The lake receives almost 50% of its water from two main surface springs located at its southern end and numerous sub-lacustrine (underwater) springs along its eastern shoreline, all of which are fed by subterranean karstic conduits draining the adjacent Lake Prespa (sq. Liqeni i Prespës; mk. Преспанско Езеро; el. λίμνη Πρέσπα) basin. There are a number of additional sub-lacustrine springs along the western side. There are also four perennial tributary rivers which drive small fluctuations of the lake’s surface level in late spring or following heavy rainfall. The lake drains towards the Adriatic Sea via the Black Drin (sq. Drini i Zi; mk. Црн Дрим) River, which originates at its northern tip, and it loses significant volumes of water (c. 40%) via evaporation. Ohrid is considered to be among the most diverse ancient lakes in the world in terms of endemic species richness.

Lake Skadar is the most extensive freshwater wetland in the Balkan region, with a surface area that seasonally fluctuates between c. 370 km² and c. 530 km². It is situated in a tectonic karstic cryptodepression and is rather shallow, with an average depth of c. five metres and maximum depth of c. 60 metres. The lake is fed by numerous sub-lacustrine karstic springs which are distributed around its periphery, and a series of affluent rivers of which the largest is the Morača. It drains to the Adriatic Sea via the short Bojana River, which also receives water from the Drin River and thus connects the system to Lake Ohrid. The precise origin of the lake remains unclear to an extent, but it is understood to have comprised a much larger wetland until c. 1,200 years ago. It is considerably more productive than Lake Ohrid in terms of fish biomass.

During the winter the Skadar Bleak aggregates in areas influenced by sub-lacustrine springs, where the water temperature remains relatively constant throughout the year. It also occurs in modified environments such as fluvial accumulation lakes and canalised river stretches.

It is an omnivorous, opportunistic forager which typically feeds close to the surface. It preys on zooplankton and free-swimming aquatic invertebrates, and also feeds on flying insects at the water surface.

The maximum recorded lifespan is c. 8 years, and sexual maturity is attained at age 2-3+.

The annual reproductive period extends from spring to summer and generally coincides with water temperatures rising above 18°C, peaking in May and June.

Adults undertake upstream or lateral migratory movements to spawn in shallow tributary riffles or along shorelines with gravel, sand or stone substrata, e.g., south and southwestern parts of Lake Skadar, northern and eastern shorelines of Lake Ohrid. The incubation period is c. 4-5 days.

This species is plausibly threatened by river regulation and other forms of anthropogenic habitat degradation throughout its range. In particular, the ongoing construction of large dams plus smaller sills, weirs and other barriers has severely altered natural flow and sedimentation regimes, blocked migration routes, fragmented subpopulations, and reduced the extent of suitable habitat for all life stages. Hydroelectric schemes have created unnatural fluctuations in discharge and water temperature (hydropeaking and thermopeaking) which bring about artificial dewatering of downstream river stretches and loss of stable nursery habitat for juveniles. 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 some spawning sites, plausibly impairing the hatching and survival rates of eggs and larvae.

The quality of habitat has been further diminished by bank stabilisation, channelisation and other efforts to enhance flood protection or exploit water resources for irrigated agriculture. Some habitats may also have been damaged by the industrial extraction of riverine gravel or other sediments for urban development.

This species is also threatened by diffuse and point source agricultural, domestic and industrial pollution, which has at some locations reduced the extent and quality of habitat due to eutrophication, siltation or discharge of toxic substances. Pollution can be particularly impactful when river discharge is reduced during the summer.

Most rivers entering lakes Ohrid and Skadar flow through areas undergoing rapid human population growth and urbanisation with insufficient water treatment systems. The lake ecosystems are thus threatened by accumulation of anthropogenic nutrients, chemicals and sediment loads from a variety of sources, including untreated domestic sewage, industry and agriculture, which are driving increased rates of eutrophication and sedimentation with an array of negative impacts on the composition of plant and animal communities.

The development of tourist facilities, increased boat traffic, and ongoing capture and pollution of karstic springs in the two basins are also of concern. Plastics and other solid wastes are regularly washed into the lakes because effective landfill sites are limited or do not meet modern standards.

In Lake Ohrid, excessive water abstraction and eutrophication in neighbouring Lake Prespa, which which it shares a subterranean hydraulic karstic connection, is believed to be partially responsible for increasing nutrient levels. In addition, the nearby Sateska River was in 1962 diverted from its former confluence with the Drin River into Lake Ohrid in order to improve the water balance of the lake and enhance its potential for hydropower generation. However, the Sateska has since become a major source of biochemical oxygen demand and sediments transported into the lake.

An observed decline in the abundance of native fishes in Lake Skadar since the mid-20^th century has been attributed to a series of factors. In particular, the construction of large hydropower dams on the Drin River has interfered with seasonal fluctuations in the lake's water level and reduced the extent of spawning and nursery habitat. Future plans include the installation of several dams on the inflowing Morača River, which supplies c. 62% of the lake's water. Furthermore, the lower Morača is polluted due to discharge of agricultural, domestic and industrial contaminants, the majority of which originate from Nikšić Polje, the Bjelopavlići Valley and city of Podgorica. The lake has thus become increasingly eutrophic since the 1970s, and this process has driven structural changes in the resident planktonic and zoobenthic communities. A number of non-native fish species have been introduced, including Goldfish (Carassius auratus), Common Carp (Cyprinus domestic strain), Grass Carp (Ctenopharyngodon idella), Eurasian Tench (Tinca tinca), Eurasian Perch (Perca fluviatilis), Eurasian Pikeperch (Sander lucioperca), Northern Pike (Esox lucius), Pumpkinseed (Lepomis gibbosus), Topmouth Gudgeon (Pseudorasbora parva), Eastern Mosquitofish (Gambusia holbrooki), Brown Bullhead (Ameiurus nebulosus) and Rainbow Trout (Oncorhynchus mykiss). All of these taxa are considered to be invasive throughout the Mediterranean region, and can exert detrimental pressures on native freshwater fauna through increased competition, predation, habitat degradation or transmission of pathogens.

Overfishing may constitute an additional threat in Lake Skadar, where Skadar Bleak landings have declined considerably since the 1970s (see 'Use and Trade').

Elsewhere, a series of mass-mortality events linked to poor nutrition and body condition have recently been observed in Albania. In the EU 27 member states, the majority of this species' range is located in a stretch of the upper Vjosa River which flows through an extensively-cultivated upland plateau, where it receives diffuse and point-source pollution from surrounding agriculture and a nearby town, respectively.

This species is harvested on a commercial basis in lakes Skadar and Ohrid, mostly during winter when adults form large aggregations at known sites (see 'Habitat and Ecology'). A number of different gear-types are employed, most frequently gillnetting, and several hundred licensed fishers operate across the two lakes, where illegal, unreported and unregulated fishing are widespread.

In the Montenegrin part of Lake Skadar it is the most economically-important freshwater fish, and is marketed fresh, processed and smoked. Landings have decreased from c. 600 tonnes per annum in the 1970s to c. 250 tonnes per annum during the early 2020s. It is also among the most important species harvested in Albania, but few reliable data are available.

In Lake Ohrid it currently comprises c. 75-80% of the annual catch in Albania and 15-20% in North Macedonia. There is no indication of a declining trend in landings.

This species is also targeted by recreational fisheries throughout its range.

No coordinated management plan exists, although closed fishing seasons and minimum catch sizes are established in lakes Ohrid and Skadar.

The North Macedonian portion of Lake Ohrid has been included in UNESCO's list of World Heritage sites since 1979, while a bilateral agreement between Albania and the Republic of North Macedonia resulted in establishment of the Ohrid Watershed Management Committee in 2004 and the Ohrid-Prespa Transboundary Biosphere Reserve in 2014. At the national scale a number of additional protected sites have been created around the lake, including the Pogradec Aquatic and Terrestrial Protected Landscape and Drilon National Monument in Albania, and the Lake Ohrid Monument of Nature and Galicica National Park in the Republic of North Macedonia. In April 2021 Lake Ohrid was added to the Ramsar List of Wetlands of International Importance (site no. 2449).

The Montenegrin part of Lake Skadar was declared a National Park in 1983 and designated a Ramsar Wetland of International Importance in 1995 (site no. 784), while the Albanian portion was nationally-protected and added to the Ramsar Convention in 2006 (site no. 1598). The lower Zeta River in Montenegro has been a protected area since 2019.

In 2023, the entire Vjosa River catchment was designated as Europe's first Wild River National Park. A number of sites in the upper Vjosa, Greece, are additionally included in the European Union's Natura 2000 network.

The Skadar Bleak is also present within the boundaries of several protected areas in the Drin River system.

A deeper understanding of this species' present distribution, abundance, population dynamics, life history and response to the ongoing threats would likely prove beneficial in the design of any structured management plan.