Megrim (Lepidorhombus Whiff-Iagonis) Populations in the English Channel and Approaches—Lactate Dehydrogenase and Glycerol-3-Phosphate Dehydrogenase Polymorphisms

Two distinct forms of the megrim, Lepidorhombus whiff-iagonis (Walbaum), exist, a southern form which ranges from the Mediterranean to the British Isles and a northern form which ranges northwards from the north of Ireland and the North Sea (Richardson, 1860; Kyle, 1913; Furnstein, 1935; Dwivedi, 1964). Kyle and Richardson considered these forms to be separate species. The southern form of megrim extends into the English Channel with Start Point, 3° 40' W, the approximate eastern limit of its distribution (Cligny, 1905). However, this fish is common only at the western entrance of the Channel since it is abundant only in depths below loom (Dwivedi, 1964). Little is known of the separate megrim populations in the geographical range of the southern form. Studies of meristic characters indicate the existence of at least three populations, one in the Mediterranean and along the coast of Portugal, another in the Bay of Biscay and the third south of Ireland and in the entrance to the English Channel (Cligny, 1905; Dwivedi, 1964).