||Fordham, S., Fowler, S.L., Coelho, R., Goldman, K.J. & Francis, M.
The spiny dogfish or spurdog Squalus acanthias is a small demersal shark of temperate continental shelf seas worldwide. Most stocks are highly migratory, but there is no regional fisheries management for the species. Management is in place in only a few range states and in only a limited part of the range of highly migratory stocks. Although naturally abundant, this is one of the more vulnerable species of shark to over-exploitation by fisheries because of its late maturity, low reproductive capacity, longevity, long generation time (25–40 years) and hence a very low intrinsic rate of population increase (2–7% per annum). Population segregation and an aggregating habit make mature (usually pregnant) females highly vulnerable to fisheries even when stocks are seriously depleted. This aggregating habit also means that catch per unit effort (CPUE) is not an adequate indicator of stock status; high CPUE can be maintained even when populations are severely depleted. Some targeted Squalus acanthias fisheries have been documented for over 100 years. Fisheries stock assessments report a decline in total biomass of >95% from baseline in the Northeast Atlantic, where catch effort is effectively unlimited. Mediterranean and Black Sea stocks are also unmanaged, with a >60% decline reported in a Black Sea stock assessment for 1981–1992. There has been a decline in biomass of mature females of 75% in just 10 years in the Northwest Atlantic, where US federal efforts to manage the stock are hampered by high bycatch, continued exploitation in Canadian Atlantic waters, and regular defiance of scientific advice by US Atlantic states. European demand continues to fuel markets around the world. Fisheries and population trend data indicate that the southern part of the Northeast Pacific stock has also declined through overfishing, but stocks appear stable off Alaska. The only data identified from the Northwest Pacific are from Japan, where landings of spurdog declined ~80% in 1952–1965, and inshore spurdog CPUE declined 80–90% from the mid 1970s to late 1990s. Unregulated and expanding target and bycatch fisheries take spiny dogfish in South America (Europe reports imports from this region), where population declines are reported. New Zealand manages the species, which is taken in target and bycatch fisheries, through its Quota Management System. There is only limited fishing pressure in Australia and South Africa, with most catches discarded.