Black Sea salmon

While Black Sea salmon were initially classified as a distinct species by the Prussian Zoologist Peter Simon Pallas in 1811, a number of analyses using genetic evidence have shown that Black Sea salmon are closely related to other brown trout lineages, with an ambiguous degree of separation. Mitochondrial DNA analysis of Salmo trutta populations overall places the Black Sea population in the Danubian lineage, alongside fish from the Caspian Sea, Aral Sea, and Persian Gulf. A later analysis of mitochondrial Cytochrome b protein genes indicated that Black Sea and Caspian Sea lineages were mostly closely related, forming a monophyletic group divergent from Atlantic, Mediterranean, Northern, and Baltic Sea lineages. Experimental crosses between Black Sea salmon and other Turkish Salmo trutta lineages reveal no evidence of reproductive isolation, with further genetic analysis revealing genetic distances between 0.002 and 0.007% within the broader Danubian lineage. Despite the large amount of evidence for Black Sea salmon as a Salmo trutta subspecies, many registers of marine species including WoRMS and the IUCN Red List list Salmo labrax as a separate species. == Distribution and range ==

Black Sea salmon are endemic to the Black Sea, the nearby Azov sea, and the rivers that drain into the Black Sea: the Firtina, Kapisre, Çağlayan, Iyidere and Solakli rivers in Eastern Turkey, the Çoruh river and its tributaries, including the Machakhelistsqali, between Turkey and Georgia, the Chanistsqali and Kintrishi rivers in Georgia, and the Mzymta river in Russia, as well as their tributaries. Some sources indicate that Salmo trutta labrax is additionally found in rivers draining into the northern and western coasts of the Black Sea, with sightings as far west as the Czech Republic. The Romanian population of Black Sea salmon is well-documented, but rare. In general, the anadromous ecotype migrates from spawning rivers to the Black Sea at one to three years old. They then remain in coastal waters for one to three additional years before returning to rivers to spawn. Conservation Status and Outlook As a largely anadromous species, the Black Sea salmon is vulnerable to disruptions in habitat and environmental conditions both in the rivers where it spawns and in the Black Sea where adults spend the bulk of their lives. While the species is overall considered to be in the "least concern" category by the IUCN, local populations throughout eastern and central Europe are considered locally at risk due to a combination of increased fisheries production and habitat disruption. Additionally, despite a ban in unlicensed fishing put in place in the 1980s, illegal fishing near the Turkey-Georgia border is common, and has put additional stress on the wild population in the southeastern Black Sea. == Biology ==

Anatomy and Physiology As smolts, Black Sea salmon are 11.5-13 cm in length. At adulthood, females are typically 38.3.8±.87 cm and males are 32.88 ± 1.825 cm from snout to the posterior end of the last vertebra (standard length). The largest recorded specimen was collected in the Firtina stream in Turkey and was 16.5 kg in mass and 98 cm in length. Typically, they have 14 fin rays in the dorsal fin, ten fin rays in pectoral fins, 14 fin rays in pelvic fins and 12 fin rays in the anal fin. While the anadromous and riverine ecotypes differ in size and behavior, they constitute a single, freely-interbreeding reproductive group. In particular, anadromous females will mate with smaller riverine males. Diet In the wild, juvenile Black Sea salmon feed mostly on small invertebrates like marine insects, while adult fish feed on smaller fishes like sprat and anchovy. Unlike other salmonid varieties, which are known for their pink flesh, Black Sea salmon flesh is typically paler. In aquaculture settings, carotenoid supplementation using astaxanthin, canthaxanthin, or lycopene has been shown to modify flesh coloration and texture, with the addition of 300 ppm astaxanthin to standard feed diets over the course of 90 days of treatment producing fish with flesh strongly visually similar to Atlantic salmon. Carotenoid supplementation also cultivated higher total protein content and lipid quality in farmed Black Sea salmon, though less is known about diet protein content in wild fish. == Aquaculture ==

Aquaculture production of Black Sea trout began in 1998 at the Adler salmon farm on the Mzymta River in Krasnodar Krai, Russia. The fish has become one of the leading aquaculture varieties in Turkey, with recorded yields of 2070 tons per year in 2018 and 2656 tons per year in 2019. By 2021, 25 different private aquaculture enterprises had been established in Turkey, in Trabzon, Rize, Artvin, Giresun, Gümüşhane and Muş. ==References==