Salmo chilo, Turan, Kottelat & Engin, 2012

Freyhof, JÖrg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, De Gruyter : 633-634

Salmo chilo

Common name. Ceyhan trout.

Diagnosis. Distinguished from other species of Salmo in Mediterranean basin by: ● dorsal head profile strongly convex / ● snout blunt / ● mouth conspicuously subterminal, with fleshly maxilla and lower lip / ○ maxilla short, depth of upper jaw 2.5–2.9 times in length of maxilla / ● size of adipose equal in male and female / ● length of maxilla equal in male and female / ○ 10–13 parr marks, distinct up to about 200 mm SL / ○ a narrow (equal or smaller than eye pupil) white ring around red spots / ○ 7–13 black spots on opercle / ○ 1–12 black spots behind eye and on cheek (more than one spot in individuals larger than about 160 mm SL) / ○ four broad bands on flank distinctive in all size groups / ○ few red spots on flank in individuals of all size groups / ○ 108–114 lateral-line scales counted until end of hypural complex / ○ 24–26 scale rows between dorsal origin and lateral line / ○ 15–17 scale rows between anal origin and lateral line / ○ 13–14 scale rows between adipose origin and lateral line / ○ 18–21 gill rakers. Size up to 300 mm SL.

Distribution. Türkiye: Göksu, Tekir, Fırnız, Göçüksu, and other tributaries of upper Ceyhan and Sarız, a tributary to upper Seyhan.

Habitat. Mountain streams, usually spring-fed, with cold, clear water and moderate currents, gravel, and pebble beds.

Biology. Spawns November–February.

Conservation status. LC.

Remarks. The very limited genomic data suggest a relatively weak genetic differentiation for this species, making it very close to or even identical to European S. farioides and S. lourosensis . Admittedly, increased sample sizes and taxon sampling will be required to assess the validity of retaining the species more rigorously. However, its genetic differentiation is weaker than that observed between other recognised trout species elsewhere.

Further reading. Turan et al. 2012b (description); Alp et al. 2003 (spawning time); Hashemzadeh Segherloo et al. 2021 (genomic data).

Lake form of Salmo caspius from Lake Çıldır in Türkiye. Recent authors have ignored the possibility that the three life-history forms of this trout might also occur in West Asia. © M. Özuluğ.

Life-history traits in trout. The diversity of trout species is often confounded due to the diversity of life-history traits. The life history of trout species follows several similar patterns and has been demonstrated to be an intraspecific diversity within all well-studied trout ( Salmo , Oncorhynchus , and Salvelinus ). It is therefore rejected that different trout species should be recognised only based on morphological characters connected to life-history types. Classically, three distinct groups of trout have been identified:

1) Anadromous trout (sea trout). These trout hatch in streams, grow there for 2–4 years, undergo smoltification and migrate to the sea or estuaries to forage. They exhibit accelerated growth and larger size than their siblings, remaining in streams. After a few years, (often after one year) they return to their native stream to spawn. Additionally, they frequently enter lower reaches of streams and rivers to overwinter in freshwater, even if they have not yet reached maturity. Sea trout are absent from the Mediterranean but occur in the Black Sea and Caspian basins.

2) Lake trout. They also hatch in streams and follow the same life history as sea trout, smoltify, and migrate to the lake to forage, grow large, and return to their native stream to spawn. This is the case in lake trout populations in West Asia, but some populations also spawn in the lake.

3) In nearly all spawning streams, some individuals do not migrate and remain there as resident trout. In West Asia, most species include only resident, non-migratory individuals.

The various life-history forms of trout are not reproductively isolated and do not represent different species. Only the resident and/or lacustrine forms are known in some species. In others, all three forms occur, and all their offspring appear to have the potential to smoltify and migrate to foraging habitats. The environmental conditions that an individual trout experiences during its lifetime influence the life-history strategy it will adopt and the life history it will develop (e.g., food availability). However, genetic factors also appear to influence whether some species, populations or individuals have the potential to develop different life histories. This plasticity of life-history strategies is observed in some populations of S. caspius and S. labrax , while most populations of these species consist of resident fish only.

In contrast to the evidence from around the world, it has been proposed that West Asian residents, lake and anadromous individuals belong to separate species that lives in the same area (i.e., behaving as distinct species as in S. labrax and S. rizeensis as well as in the four Kura-Aras species listed in this book). The hypothesis of one species with two life-history forms (migratory and resident) has not been tested nor rejected in both cases. The close relationship of S. labrax and S. rizeensis demonstrates the need for a review based on many populations and high-resolution molecular methods. Based on a small sample size and genomic data, it had been suggested that they are conspecific and should be treated as one species as soon as further studies confirm these data. The case of the trout species in the Kura and Aras rivers will require further investigation in the future. However, it is anticipated that only one species will be identified. Further reading. Turan et al. 2010 (Black Sea trout); Ninua et al. 2018 (Cytochrome b data); Hashemzadeh Segherloo et al. 2021 (genomic data); Turan et al. 2022b (Caspian trout).

Salmo ekmekciae ; DegirmenÖzü in KÖprüçay drainage, Türkiye; 330 mm SL.© J. SchÖffmann.