Presentation on theme: "It moves as you go... baselines in Limfjorden environmental history DK INCOFISH unit: Poul Holm Bo Poulsen Anne H. Marboe Department of History and Social."— Presentation transcript:
It moves as you go... baselines in Limfjorden environmental history DK INCOFISH unit: Poul Holm Bo Poulsen Anne H. Marboe Department of History and Social Theory University of Roskilde INCOFISH, WP2 Workshop Tallin, 3 March 2006
Salinity 5000BP s.
Limfjord baselines c Mussel scraping Suffering from depletion of grounds Mussel & oyster farming No other commercial fishery Some angling Data: gov. Statistics, ongoing sci. surveys
Baselines c Commercial fishing for –Eel –Plaice –Herring Cradle of modern Danish fishing –Most important fishing area in DK until c Regime shift c Data: gov. Stats., pioneering mar. Bio. In 19th c.
Lif Jacobsen The Limfjord fishery: Economic and ecological explanations for the collapse of the 1920´s Key events in the Limfjord fishery ( ): 1888 First national Fishery Law Introduction of motor driven boats in the fisheries around Increasing number of fishermen. Increasing amount of fishing gear. 1923/25 Legislation of motor driven winches for pulling seines onboard. Focus on the main species: Eel, plaice, cod and herring Based on: The Danish Annual Fishing Report Copy of The Fishing Controls correspondence, etc Reports from The Danish Biological Station etch
Growing fishing effort, Due to the increasing number of: Fulltime fishermen. Motor driven boats (from 1905) Amount of fishing gear. ( standing gear )
Relationship between effort, cost and yield. The interrelationship between the various objectives. Source: Cunningham m.f.: Fisheries Economics an introduction.p.118. TC, (total cost) and Effort continually increasing. SMEY, (static maximum economic yield) reached by TR, (total revenue) become smaller due to a negative development in prices (from 1917) f oa, (bio economical equilibrium) reached by MSY, (maximum sustainable yield): ?
Baselines c s Period of transition Commercial fishery –Herring collapse –Eel crisis –Whitefish disappears –Emergence of plaice –Emergence of Aurelia Invention of Danish seine
North Sea breach in 1825
Baselines c Phases of very large herring fisheries Also commercial fisheries for: –Eel (Anguilla anguilla) –Whitefish, (Coregonus lavaretus) Data: pre-stat. era; but proxy data from historical archives
400 years of catching herring
Time series of fishing effort Pound nets
Seines in different areas
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Baseline(s) report Same water - very different ecosystems over 4 centuries Causes of change? Depending on baseline Regime shifts Fishing mortality Climate change Hydrographic change Episodic events Societal changes