The Changing British Fish Fauna

Abstract

INTRODUCTIONS of foreign species, the results of which deserve close scrutiny, are not confined to mammals. Rainbow trout are now a permanent element in our fauna, black bass are established in certain places, and now the case of the pike-perch in East Anglia deserves to be put on record. On March 4, 1934, a Lucioperca of 11¾ lb. was caught in the River Delph, near Welney, in the Ouse basin, and was brought here for identification. Five species of the genus are known, two in the rivers and lakes of eastern and northern Europe, one in the Black and Caspian Seas, and two (placed by some authors in a separate genus Stizostedion) in Canada and the northern U.S.A. Comparison with specimens in the B.M. (Nat. Hist.) revealed that the Welney fish resembles the American species in five characters and the European in four, but in view of the structural importance of the American characters (especially the distance between the pelvic fins) it is reasonably certain that it came from the American species Lucioperca vitrea, Mitchill.