Alosa immaculata, Bennett, 1835

Alosa immaculata View in CoL View Figure

Common name. Large Black Sea shad.

Diagnosis. Distinguished from other species of Alosa entering freshwater in Black Sea basin by: ● 36–69 gill rakers, longer than branchial filaments / ○ teeth on palatine and vomer well developed. Size up to 350 mm SL.

Distribution View Figure . Black and Azov Seas, from where adults ascend rivers and migrate far upstream to spawn. Presence in Marmara basin questionable. Present in Rioni, but distribution in northern Anatolia poorly known. Used to ascend Danube for about 1600 km to Mohacs ( Hungary), Don for 900 km to Oust-Medveditskaya, Dniepr to Kyiv, Dniester to Yampol, and South Bug to Voznessensks.Reported to spawn in Kuban below Krasnodar dam since 1983. A landlocked population occurs in Don.

Habitat. At sea, pelagic, in deep water. Migrates to middle reaches of large rivers, spawning where current is strongest, near surface, usually at 2–3 m depth in main channel.

Biology. Anadromous, migrating upstream to spawn at three years, rarely earlier. Few individuals spawn two seasons. Appears along coast in March–April, enters rivers when temperatures reach about 6–9°C between late March and late April. Migration usually peaks in May. Spawning begins when temperatures rise above 15°C in April–August. Spawns usually in afternoon (1–8 pm), eggs pelagic. Spent individuals return to sea to feed.Juveniles inhabit floodplain and shallow riverine habitats, migrating to sea or estuarine habitats during first summer; move to sea in autumn and remain there until maturity. At sea,it feeds on a wide variety of zooplankton (especially crustaceans) and small fish.

Conservation status. VU; damming of major rivers significantly reduced available spawning habitat and migration routes in 20 th century. Decline appears to be continuing due to severe overfishing. Largest population in Danube.

Further reading. Kolarov 1991b (biology; as A. pontica ); Kottelat 1997 (systematics).