Smelt in the River Tamar in Cornwall, England.

Smelt (Osmerus eperlanus)

Smelt are found in estuaries and coastal waters along the Atlantic coast of Europe and northwards along the coast of Russia. Smelt are related to trout and salmon and have in common with these species a second small, fleshy dorsal fin called an adipose fin. They can be recognised by their somewhat toothy appearance and their unusual smell, which is very like cucumber. 

Smelt migrate into the upper reaches of estuaries in spring to spawn in tidal freshwater sections of rivers. The young move down into estuaries after hatching, feeding on zooplankton, and adults feed on larger prey, such as shrimp and small fish. In Ireland, the conservation status of smelt was long classified as vulnerable because they were only known from the Shannon Estuary, but surveys have confirmed that there are populations found in several other estuaries of large river systems around the island. 

Threats to smelt in Ireland include fishery for their use as live bait, poor water quality and dredging in rivers that they depend on for spawning sites.