River Tywi these fish to over in weight. In summer and autumn there is also a substantial run of Atlantic salmon ("Salmo salar"). In May the Tywi has a run of the rare and protected twaite shad ("Alosa fallax") and allis shad ("Alosa alosa"). The Tywi also contains brown trout, eels, pike, and a variety of small fish species, and is home to brook lampreys, river lampreys and sea lampreys. The Tywi has the distinction of having accidentally produced by far the biggest fish ever taken on rod and line in fresh water in Britain. This was a sturgeon ("Acipwienser sturio") weighing
West African pygmy herring West African pygmy herring The West African pygmy herring ("Sierrathrissa leonensis") is a very small fish, reaching a maximum length of SL, is a member of the herring family Clupeidae, and belongs to a radiation of the subfamily Pellonulinae in the freshwater systems of western and central Africa that includes such species as the "Microthrissa royauxi" of the Congo River basin and "Limnothrissa miodon" of Lake Tanganyika. It is the only species of its genus. A very small fish which shows a reduction in size and some neoteny when compared to its larger relatives. The West African pygmy herring is