#salmoniformes

Many salmonid species are considered keystone organisms important for both freshwater and terrestrial ecosystems, due to their middle position in the food chain creating a biomass transfer from oceanic to inland waterbodies.

The Bering Cisco (Coregonus laurettae) may migrate as far as 2,100 kilometres (1,300 mi) inland to spawn in remote, pristine rivers. They do not feed during their migration, which is typical among salmon, but rare in whitefishes. It takes 4-9 years for young Bering Cisco to reach maturity.

The Pollan (Coregonus pollan) is a freshwater whitefish known only from five Irish lakes: Lough Neagh, Lower Lough Erne, Lough Ree, Lough Dergand Lough Allen. The Pollan is endangered, facing competition from introduced, invasive species such as Northern Pike (Esox lucius), Roach (Rutilus rutilus), and Zebra Mussel (Dreissena polymorpha). The population of Pollan relies on captive breeding and restocking of its endemic Irish lakes for survival.

Bear Lake is a freshwater lake on the Idaho–Utah border in the Western United States, about 109 square miles (280 km2) in size. Bear Lake has a high rate of endemism (native species not naturally found anywhere else), many of them being Salmoniformes. These include the Bonneville Cisco (Prosopium gemmifer), Bonneville Whitefish (Prosopium spilonotus), and Bear Lake Whitefish (Prosopium abyssicola), as well as a unique population of Bonneville Cutthroat Trout (Oncorhynchus virginalis utah). There have been attempts to transplant these species to other areas without success, with the exception of Bear Lake’s Cutthroat Trout strain. Invasive Lake Trout (Salvelinus namaycush) have been introduced to Bear Lake, in an attempt to give fishermen more variety, but the Lake Trout both feed on and compete with the endemic fish.

The Inconnu, also called Sheefish, Ak Balyk, or Beloribitsa (Stenodus leucichthys), is a freshwater whitefish originally native to the Caspian Sea. However, it is extinct in the wild, and exists only in fish hatcheries, with populations only maintained by stocking. The Inconnu used to migrate 3,000 kilometres (1,900 mi) upstream from the Caspian to their main spawning grounds, the Kama River, until dam construction, particularly of the Volgograd Dam in 1959, completely impeded the migration and natural reproduction of this species. There have been no efforts to reestablish their natural migration routes. The introduction of invasive Mnemiopsis comb jellies into the Caspian, which compete with the Inconnu for prey, also contributed to their decline.

Some populations of Nelma (Stenodus nelma) (image 3) do not migrate, spending their entire life in freshwater instead.

Like Bear Lake, the much larger (and MUCH deeper) Lake Baikal of Russia also has endemic salmonids. These include the Omul (Coregonus migratorius), Baikal Whitefish (Coregonus baicalensis), Baikal Black Grayling (Thymallus baicalensis), and Baikal White Grayling (Thymallus brevipinnis). The Omul specifically is considered a delicacy, and is the object of one of the largest commercial fisheries on Lake Baikal.

As they are highly sensitive to changes in water quality, Graylings (genus Thymallus) may be considered indicator species: a species which can reveal the qualitative status of the environment. The Arctic Grayling (Thymallus arcticus) (image 2) has largely disappeared from many of the Southernmost parts of their former range.

The Arctic Grayling is one of the main food sources for the Iñupiat People of the Alaska North Slope.

Lake Ohrid, which straddles the mountainous border between the southwestern part of North Macedonia and eastern Albania, is yet another lake with endemic salmonids. Lake Ohrid is one of Europe's deepest and oldest lakes, giving its 200+ endemic species plenty of time and room to speciate! However, both of Lake Ohrid’s salmonids, the Ohrid Trout (Salmo letnica) and the Belvica or Belushka (Salmo ohridanus), are endangered due to heavy fishing, intentional hybridization, and degradation of water quality.

Atlantic Salmon (Salmo salar) are very popular as a food fish, and overfishing as well as habitat destruction has impacted the population in some areas. As a result, the species is the subject of conservation efforts in several countries, as well as the focus of aquaculture (fish farming) in many countries. At present, Norway produces over 50% of the farmed world supply of Atlantic Salmon.

The Siberian Taimen (Hucho taimen) is the largest salmonid, with an average length of 70 - 120 cm (2.3 - 4 ft) and weight of 15 to 30 kg (33 to 66 lb). The largest ever recorded, supposedly caught in the Kotui River in Russia in 1943, was 210 cm (6.9 ft) long and weighed 105 kg (231 lb). Siberian Taimen can live up to 55 years or more, and adults can go after terrestrial prey such as rodents and birds.

One Mongolian legend tells of a gigantic Taimen trapped in river ice. Starving herders were able to survive the winter by hacking off pieces of its flesh. In the spring, the ice melted and the giant taimen climbed onto the land, tracked down the herders, and ate them all.

The Lake Trout (Salvelinus namaycush) is known by many common names, including Mackinaw, Namaycush, Lake Char, Touladi, Togue, Laker, Grey Trout, Siscowet, Paperbelly, Lean, and Mud Hen. Lake Trouts are known to sometimes naturally hybridize with the Brook Trout (Salvelinus fontinalis) (image 1), and these hybrids are called Splakes (male brook with female lake) or Brookinaw (male lake with female brook). These hybrids are normally sterile, but self-sustaining populations exist in some lakes.

The Jaunet (Salvelinus neocomensis) was a deepwater char species endemic to Lake Neuchâtel of Switzerland. The last specimen was fished up in 1904; research undertaken in the 1950s and 2003 failed to find evidence of the survival of this species after the last reported specimen. Deepwater char are highly sensitive to changes in the quality of the water, and the extinction of the Jaunet may have been due to economic development around the lake.

The critically endangered Sakhalin Taimen (Parahucho perryi) of Russia and Japan is the only living member of its genus. It is one of the largest, most ancient salmon species, with fossils of the genus dating back to the mid-Miocene. Degradation of the Sakhalin Taimen’s environment by logging, oil exploration, and change of land use to agriculture have contributed to its decline, and the fish is also caught as bycatch and by recreational anglers. Present populations are estimated to be less than 5% of their historic levels.