Biology and Management of Dogfish Sharks

32. Sequel of the Directed Fishery for Spiny Dogfish (Spurdog) in the 1980s off the West Coast of Ireland

Edward Fahy, Peter Green, Lisa Borges, Ayesha Power, and Edgar McGuinness

doi: https://doi.org/10.47886/9781934874073.ch33

Abstract.—The Northeast Atlantic contains one stock of spiny dogfish Squalus acanthias (also known as spurdog), which has been in decline since the 1960s. Landings reached a peak of 55,600 metric tons (mt) in 1963; 24 years later they had fallen to 44,600 mt and 12 years after that to 9,800 mt. The last phase of steep decline commenced in 1987 and coincided with heavy landings from mainly the Celtic Seas of which Ireland took a substantial share in a gill-net fishery off its southwest coast. At first the Irish gill-net fishery harvested predominantly female and pregnant spiny dogfish but the characteristics of the landings rapidly changed.

Biological data from the southwest Ireland spiny dogfish fishery of the late 1980s are reviewed and additional data are assembled on commercial landings (to 2004), landings per recreational rod-angler-day (1978–2004), indications of the location of newly born pups from discard surveys and the changing distribution of pregnant females (1955–2004). The southwest Ireland fishery was conducted on an important pupping ground in the Celtic Sea. Tagging work demonstrated that the species follows a slow, clockwise migration northwards along the west coast of Ireland and eventually into the North Sea. Two pulses of recruitment, the second much smaller than the first, are tentatively identified, although the rapid fluctuations in the biological characteristics of the landings may indicate a more complex pattern.

Female spawning stock biomass was targeted in the Irish gill-net fishery of the 1980s. Large females subsequently disappeared from the sea area to the north of the fishery. An argument is made that the Irish gill-net fishery intercepted migrations of dogfish to the North Sea.