Caspian Lamprey

The Caspian lamprey (Caspiomyzon wagneri) is a parasitic jawless fish endemic to the Caspian Sea basin, found along the coasts of Russia, Kazakhstan, Azerbaijan, Turkmenistan, and Iran. It is the sole species in its genus and one of the few lampreys adapted to a large inland brackish sea rather than the open ocean. Adults spend their feeding phase in the Caspian Sea, attaching to other fish with a toothed sucking disc, before migrating up rivers such as the Volga and Kura to spawn in freshwater gravel beds. As with other lampreys, it belongs to the ancient jawless fish lineage Petromyzontiformes, lacking true jaws, paired fins, and a bony vertebral skeleton. Historic dam construction on its spawning rivers has reduced its range.

• Elongated, scaleless, eel-like body, dark grey to blue-black above, lighter below
• Circular sucking-disc mouth with concentric rows of sharp, pointed teeth
• Seven round external gill openings behind the head
• Continuous, low dorsal fin extending toward a rounded tail
• Adult length typically 30-55 cm, among the larger lampreys of its region

The Caspian lamprey can be distinguished from smaller non-parasitic brook lampreys in its basin by its greater size, well-developed rasping teeth, and darker overall coloration, along with its habit of migrating between the Caspian Sea and freshwater rivers.

Caspian lampreys are anadromous, spending their adult feeding phase in the brackish waters of the Caspian Sea, the world's largest inland body of water, and migrating into connecting rivers such as the Volga, Ural, Kura, and Terek to spawn. In the sea, they range over open water and coastal areas where suitable host fish occur, while spawning migrations take them far upstream into freshwater sections with gravel or rocky bottoms. Larvae then burrow into soft river sediment for several years before transforming into adults. Historic damming of major spawning rivers has blocked migration routes and reduced available breeding habitat, affecting the species across parts of its range.

As adults in the Caspian Sea, Caspian lampreys behave as parasites, attaching to other fish with their toothed sucking disc and feeding on blood and tissue fluid over an extended period. When ready to spawn, they cease feeding and undertake an upstream migration into freshwater rivers, sometimes covering long distances against strong currents. On reaching suitable gravel riffles, pairs build simple nests by shifting stones, spawn, and then die, a single-reproduction life-history pattern typical of lampreys. Larvae are sediment-dwelling filter feeders, straining algae, detritus, and microorganisms from river substrate for several years. The species links the Caspian Sea and its tributary rivers ecologically, cycling nutrients between marine and freshwater systems.