Salmo labrax

Common name. Black Sea trout.

Diagnosis. Distinguished from other species of Salmo in Marmara, Black Sea and Caspian basins by: ○ background colour of flank brownish to silvery in life (silvery in anadromous individuals) / ● black spots on flank ocellated, few and scattered on upper third of flank in most individuals, number not increasing with size and age / ○ red spots few or many, usually irregularly shaped and ocellated / ○ number of red spots on flank increasing by size in male / ● head about 0.9–1.2 times in body depth at dorsal origin / ○ maxilla short, reaching slightly beyond posterior eye margin in individuals larger than 150 mm SL, upper edge convex posteriorly ○ body depth at dorsal origin 23–27 % SL / ● dorsal in front of midpoint of body / ○ 110–121 lateral-line scales counted until end of hypural complex / ○ 27–32 scale rows between dorsal origin and lateral line / ○ 15–23 scale rows between anal origin and lateral line / ○ 16–20 gill rakers. Size up to 1150 mm SL.

Distribution. Marmara and Black Sea basins.

Habitat. At sea, at depths of down to 50 m, usually along coasts and near estuaries. Migrates to mountain streams. Locally resident in lakes. Resident part of populations in streams with fast currents, cold, clear water, and stony or gravelly bottoms. Usually in lower and middle reaches of main rivers and streams. Also, in very short coastal streams (less than 5 km). Observed in Çoruh up to 340 km from sea. Usually spawns in middle reaches of rivers.

Biology. Anadromous, lacustrine, and resident forms, with most individuals remaining in freshwater. Smallest adult female recorded about 160 mm SL. Spawns October– January. Spends 2–4 years in rivers and streams, then smolts migrate to sea or matures in freshwater. Spends 2–4 years at sea. Some anadromous individuals return to rivers in April–May, where they spend summer, usually spawning migration starts in September–October, gregarious during migration. Other anadromous individuals begin to migrate shortly before spawning. Eggs hatch in 6–8 weeks. Parr and resident adults feed on a wide variety of aquatic and terrestrial invertebrates. Anadromous and large resident individuals feed mainly on fish and large crustaceans. Anadromous individuals feed in rivers.

Conservation status. LC.

Remarks. Salmo labrax, S. coruhensis, and S. rizeensis are often recognised as three species from the Black Sea basin. Genomic data suggest they did not differentiate earlier than during the last or pre-last glacial period. They occur in many sedentary populations, some of which are also occasionally or frequently anadromous. All are closely related by recent genomic data and microsatellite and cytochrome b mtDNA studies. Furthermore, the morphological differences described between the species are minor and overlapping. We follow the latest study on this species complex and treat S. coruhensis as a synonym of S. labrax but keep S. rizeensis as a valid species. That means S. rizeensis is not the resident form of S. labrax, but resident populations of two species occur in sympatry.

Further reading. Berg 1949b (biology); Salmanov & Dorofeyeva 2001 (morphology); Bernatchez 2001 (genetics); Turan et al. 2010 (description of S. coruhensis); Ninua et al. 2018 (Cytochrome b data); Hashemzadeh Segherloo et al. 2021 (genomics); Ninua et al. 2023 (synonymy of S. coruhensis, microsatellite data).