Basking Shark (Cetorhinus maximus) fishing in Ireland 1947–1987.

A description of the spatial and temporal extent of the Basking Shark fishery in Irish waters is presented, based on a combination of interviews, published literature, newspaper archives, and ICES catch records. Both Irish and Norwegian vessels participated in this most recent, and poorly documented, phase of the Irish Basking Shark fishery, from 1947 to 1987. Two areas were consistently fished: the Galway/Mayo and Waterford/Wexford coasts, although fishing occurred all around Ireland. Irish vessels stopped targeting Basking Sharks in 1984 while Norwegian vessels fished them at least until 1987. When cross-referenced with other sources, ICES records overestimated 1957–1959 fishing mortality but underestimated it in other years because landings by Irish vessels were omitted. Minimum landing totals for sharks caught around Ireland were estimated at 14,373, of which the majority were taken by Irish vessels (net fishery: n=12,580, harpoon fishery: n=661) and 1,132 were taken by Norwegian vessels. Newspaper articles (n=43) were used to estimate undocumented catches by extrapolating catches based on the size and capacity of the fleet. The extrapolated estimate for Basking Sharks taken around Ireland and landed by Norwegian vessels (1957–1987) was n=6,160. However, the true total catch by all vessels in Irish waters (documented and estimated from vessel visits reported in newspapers) may have been as high as 19,401. Interviews provided important technical context to aid the interpretation of the data, including a struck-and-lost rate of 10 %. Correcting the figures for losses and undocumented catches around Ireland during 1947–1987 (based upon minimum fishing effort estimates and assuming profitable catches), the estimated catch total ranged between 15,810 and 21,343 sharks respectively. Such a large Basking Shark fishing mortality is a conservation concern, particularly given the genetically distinct population previously identified off the southwest of Ireland.