|UK fisheries, climate change and North Sea fishes: a long-term perspective|
Kerby, T.K. (2013). UK fisheries, climate change and North Sea fishes: a long-term perspective. PhD Thesis. University of East Anglia: Norwich, UK. 143 pp.
20th century; Brill; Climate change; Commercial fisheries; Demersal fisheries; Distribution; Landings; Time series; Trends; Turbot; Whiting; Merlangius merlangus (Linnaeus, 1758) [WoRMS]; Scophthalmus rhombus (Linnaeus, 1758) [WoRMS]; ANE, North Sea [Marine Regions]; ANE, North Sea, UK Sector; Marine
North Sea demersal fishes and fisheries have changed over the past 100 years. To detect the main factors driving these changes, long-term data are needed. Using historical fisheries data that extend throughout the 20th century, this thesis aims to assess drivers influencing developments in fisheries as well as changes in the distribution and abundance of commercially important fishes in the North Sea.For English demersal fisheries, favourable political, technological and economical drivers were identified, inducing a vast rise in English fisheries in the first half of the 20th century; however, the same drivers, acting adversely, influenced the decline in recent decades and the emphasis of fisheries shifted from England to Scotland.Different trends in distribution were observed for North Sea whiting, turbot and brill between the 1920s and 2000s. Whiting distribution shifted westward between the late 1940s and 1960s, whereas turbot nearly disappeared from the northern North Sea from the 1970s onwards. Brill distribution remained rather stable in the central and southern North Sea. The reasons for the longitudinal shift of whiting remained unclear as the relationships to two potential drivers, climate change and fishing pressure, were not strong. For turbot, the cause for the near disappearance from the northern North Sea is inconclusive.Commercial fisheries data were assessed reliable for distribution analysis when comparing commercial data of whiting, a commonly discarded species, and unbiased survey data. Whiting, compared to flatfish, is of secondary commercial importance. In areas where discrepancies occurred between commercial and survey data, higher discarding of whiting is suggested, as highly priced flatfish are caught there.This thesis demonstrates past conditions of demersal fish populations and fisheries in the North Sea and presents the effects of different drivers on them. The documented changes in fishes and fisheries contain valuable information for resetting baselines and developing appropriate management strategies.