Global and European regional assessment: Endangered (EN)
EU 27 regional assessment: Endangered (EN)

The Prespa Bleak has a restricted range (extent of occurrence (EOO) c. 1,592 km²), which meets the threshold for Endangered under Criterion B1 (EOO < 5,000 km²). It is present at two locations where the extent and quality of habitat are estimated to be declining. Therefore, this species is assessed as Endangered under Criterion B (B1ab(iii)), both globally and for the EU 27 Member States.

This species is endemic to the Lake Prespa (sq. Liqeni i Prespës; mk. Преспанско Езеро; el. λίμνη Πρέσπα) transboundary basin, which is shared by Albania, the Republic of North Macedonia and Greece.

A subpopulation inhabiting the Gjancit accumulation lake in the upper Osum River system, Albania, appears to have been artificially translocated.

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, but it remains among the most abundant native fish inhabiting the Prespa Lakes basin, and there is limited evidence to suggest it may be slowly increasing in Lesser Prespa.

The Prespa Lakes basin lies at 850 metres AMSL and is a hotspot for endemic biodiversity including freshwater fishes and migratory birds. It comprises two relatively shallow interlinked lakes; the larger (el. Μεγάλη Πρέσπα; mk. Преспанско Езеро; sq. Liqeni i Prespës së Madhe) and Lesser Prespa (el. Μικρή Πρέσπα; mk. Мало Преспанско Езеро; sq. Prespa e Vogël), which are separated by a narrow strip of alluvial land.

It partially drains to nearby Lake Ohrid (sq. Liqeni i Ohrit; mk. Охридско Езеро), and by extension the Drin  (sq. Drini; mk. Дрим) River system, via subsurface karstic conduits.

The Prespa Bleak is largely pelagic and feeds on phyto- and zooplankton, but migrates short distances to shallow shorelines with substrates of gravel or coarse sand to spawn. In Greater Prespa, some individuals also spawn in tributary streams, with migration occurring exclusively at night. Spawning takes place when conditions are favourable from April to August, peaking in May and June.

This species is believed to hybridise with the sympatric Dalmatian Roach (Leucos basak).

It is among the primary prey items of piscivorous water bird colonies which nest at the lakes, including Dalmation and White Pelicans (Pelecanus spp.), Great Cormorant (Phalacrocorax carbo) and Pygmy Cormorant (Microcarbo pygmaeus).

The Prespa Lakes have been partially modified. They are connected by a man-made channel excavated through the alluvial isthmus which separates them, on which a controllable sluice is installed and was reconstructed in 2004. In addition, a minor natural outflow from the Agios Germanos River delta to Lesser Prespa was blocked during the 1930s and has not been re-established, reducing the volume of water that flows into the lake.

In Albania, Lesser Prespa was for a number of years artificially connected to the Devoll River via the so-called Prespa Canal Scheme in order to abstract water for irrigation purposes, but the project was abandoned and the canal filled in during the early 2000s after it failed to function as planned. During the period that the canal was open, sedimentation in the southern portion of Lesser Prespa increased drastically, leading to a pronounced reduction in water depth and expansion of reedbeds.

Water abstraction for agricultural and domestic usage continues to take place throughout the basin, and has been cited as the central cause for the continued diminishing water level in Greater Prespa, which has receded by at least eight metres since the mid-20^th century. However, climate change is also a primary driver, with a significant decrease in tributary discharge, winter precipitation and snowfall observed since the 1960s. The situation is so drastic that the sluice gate between the lakes has to be kept closed at all times in order to maintain the water level in Lesser Prespa, which is now located at a higher altitude than Greater Prespa and would otherwise drain into it.

The reduction in water volume, coupled with an increase in nutrients, toxic substances and solid materials (including plastics) entering the lakes from surrounding farmland, industry (small-scale food processing, poultry farming, textiles, metal and wood processing, civil construction, ceramics and chemical production), illegal landfills, fly-tipping and untreated domestic wastewater has resulted in escalating eutrophication. This is particularly evident in Lesser Prespa, where blooms of toxic cyanobacteria now occur on a regular basis during the months of summer and autumn.

Construction of small dams on streams draining into Greater Prespa has blocked access to some spawning grounds formerly used by native fishes, with additional projects planned.

Moreover, no fewer than 13 non-native fish species have been introduced to the Prespa basin, of which at least six have become established. These include the Topmouth Gudgeon (Pseudorasbora parva), Pumpkinseed (Lepomis gibbosus), Common Carp and European Bitterling (Rhodeus amarus), all of which are considered invasive and can exert detrimental pressures on native freshwater fauna through increased competition, predation, habitat degradation or transmission of pathogens.

Although sometimes cited as such, predation by waterbirds does not constitute a plausible threat to native fishes in the Prespa ecosystem.

This species is harvested commercially and sold to local restaurants or exported to regional wholesalers. It is among the most important components of the Prespa Lakes inland fishery alongside the native Prespa Nase (Chondrostoma prespense) and Dalmatian Roach (Leucos basak), plus introduced Common Carp (Cyprinus domestic strain). In Greater Prespa it is specifically targeted on winter nights via a unique fishing method which employs cast nets equipped with small lights.

The total number of fishers in the Prespa basin has declined considerably since the late 20^th century, and most traditional fishing methods have been abandoned since the early 2000s. Models of fishing sustainability suggest that historic offtake has been reasonable, and the current level does not constitute a plausible threat.

No specific conservation management plan exists, but a number of protected areas lie within the boundaries of its range. The entire Prespa Lakes basin falls within the limits of the Prespa Park, the first transboundary protected area in the Balkan Peninsula. The Prespa Park was established in 2000 in response to environmental concerns regarding the lakes, following a joint trilateral declaration by all three bordering countries, but was not formalised until 2017. The lakes are also surrounded by four National Parks, and two sites within the basin are included in the European Union's Natura 2000 network of protected areas. In addition, both lakes are designated as Wetlands of International Importance by the Ramsar Convention on Wetlands.

Since 2005, the Prespa Park Management Body controls the volume of water exiting Lesser Prespa to Greater Prespa by regulating the outflow discharge on the artificial channel connecting the two lakes. The environmental organisation 'Society for the Protection of Prespa' currently coordinates a transboundary environmental monitoring system within the Prespa basin, which includes tri-annual fish surveys. The European Union co-funded LIFE project 'Prespa Waterbirds' (LIFE15 NAT/GR/000936) ran from 2016-2021 and aimed to contribute to waterbird conservation in Lesser Prespa via a series of actions, including a specific plan to improve "spawning grounds and access for fish species". Specific actions included the clearing of sediment and reedbeds from around the mouths of tributary streams to facilitate the passage of migratory fishes.

An earlier LIFE project (LIFE2002 NAT/GR/8494) also targeting bird conservation took place from 2002-2007 and aimed to "increase fish spawning grounds", while the Global Environment Facility project 'Integrated Ecosystem Management in the Prespa Basin in Albania, FYROM and Greece' ran from 2006-2011. Furthermore, a LIFE+ Information and Communication Project entitled 'Fish, Fisheries & European Policy' in the Prespa Basin (LIFE09 INF/GR/000319) was funded from 2010-2013 with the objective to "promote the conservation of the threatened endemic and rare fish fauna of the area and the implementation of sustainable fishery practices".

The introduction of non-native species to the Prespa Lakes has been outlawed, and strict annual catch limits are in place for the native fishes of commercial interest. Fishing of any kind is also forbidden during mid-to-late spring, when native fish species spawn. Fly-tipping, disposal or processing of any kind of waste, discharge of untreated waste water, shoreline construction, excavation of sand or gravel, unlicensed use of lake water, uncontrolled cutting of trees and forests, and inappropriate utilisation and burning of pastures have all been prohibited.

This species' population status, life history, habitat preferences, and response to the ongoing threats in the Prespa basin are poorly understood, and further research is required.