“…Since the early work of Heincke (1 898) demonstrated consistent phenotypic differences between herring, Clupea harengus, groups in the north-eastern Atlantic, investigators have studied morphometric and meristic variation in herring in attempts to define population structure (Dutt, 1958;Krefft, 1958;Wood & Foster, 1966;Postuma, 1974;Grainger, 1976;Wood, 1979;Rosenberg & Palmen, 1982). The primary purpose of the present study was to elucidate the population structure of the herring resources to the west of the British Isles and in particular those of the north Irish Sea.…”