This essay discusses the import of cod (Gadus morhua) in Sweden during the Middle Ages through isotope analysis of cod vertebrae. The isotope analysis is used to trace the cods origin to either the Baltic Sea or the Atlantic Ocean. The bones were subjected to d13C, d15N and d34S analysis; 64 of  the analyzed bones met the quality criteria. The isotop data showed that import of Atlantic cod was significant in medeval Sweden. The analysis suggests that there is no specific time or event that the sites start to import cod but this varies from site to site.

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This essay discusses the import of cod (Gadus morhua) in Sweden during the Middle Ages through isotope analysis of cod vertebrae. The isotope analysis is used to trace the cods origin to either the Baltic Sea or the Atlantic Ocean. The bones were subjected to d13C, d15N and d34S analysis; 64 of  the analyzed bones met the quality criteria. The isotop data showed that import of Atlantic cod was significant in medeval Sweden. The analysis suggests that there is no specific time or event that the sites start to import cod but this varies from site to site.

<p>Three different laboratory studies have been carried out in order to elucidate the interactions between two predators and their prey in the Fucus vesiculosus community. The first study investigated the behavioural response of Gammarus oceanicus, Idotea baltica and Palaemon adspersus in the chemicai presence of their predators Gadus morhua and Perca fluviatilis. A lowering of night activity among the crustaceans was expected. The second study was carried out in 1 m³ mesocosm-tanks were the predators had the opportunity to actively prey on both I. baltica and G. oceanicus among live F. vesiculosus plants. This experiment lasted före one week and the decrease of the crustaceans during this period was noted as result. In the third study was the predators ability to forage in complete darkness investigated. This was carried out in the same mesocosm tanks but without Fucus and for 5 hours. None of the crustacean species decreased their night activity as response to the smell of the predators. This may indicate that chemically mediateda signals are of less importance in the Fucus community due to high turbulence and swift waterexchange in this splashzone habitat.  Cod consumer more of both G. oceanicus and  I. baltica than perch in the two different foraging-studies. In these conditions the cod was the most efficient predator. The decreased stocks of cod was the most efficient predator. The decreased socks of cod in the Baltic Sea may have reduced the top-down control in the foodweb of the fucus community.</p><p> </p><p> </p>

Three different laboratory studies have been carried out in order to elucidate the interactions between two predators and their prey in the Fucus vesiculosus community. The first study investigated the behavioural response of Gammarus oceanicus, Idotea baltica and Palaemon adspersus in the chemicai presence of their predators Gadus morhua and Perca fluviatilis. A lowering of night activity among the crustaceans was expected. The second study was carried out in 1 m3 mesocosm-tanks were the predators had the opportunity to actively prey on both I. baltica and G. oceanicus among live F. vesiculosus plants. This experiment lasted före one week and the decrease of the crustaceans during this period was noted as result. In the third study was the predators ability to forage in complete darkness investigated. This was carried out in the same mesocosm tanks but without Fucus and for 5 hours. None of the crustacean species decreased their night activity as response to the smell of the predators. This may indicate that chemically mediateda signals are of less importance in the Fucus community due to high turbulence and swift waterexchange in this splashzone habitat.  Cod consumer more of both G. oceanicus and  I. baltica than perch in the two different foraging-studies. In these conditions the cod was the most efficient predator. The decreased stocks of cod was the most efficient predator. The decreased socks of cod in the Baltic Sea may have reduced the top-down control in the foodweb of the fucus community.

<p>The Barents Sea contains one of the most productive marine areas in the world. For centuries, Northeast Arctic cod and Norwegian spring spawning herring have been of vital importance for the Norwegian fish export industry and hence economic growth in Norway. It has been common knowledge that the biomass of different Barents Sea species experiences both shortand long-term fluctuations. These fluctuations have been explained by changes in herring cycles and cod cycles, or by the introduction of new fishing equipment, and more. Norwegian marine research began in earnest at the beginning of the 19th century. The main task for researchers was to discover how nature influenced cod stocks and the effects these fluctuations had on the lives of people who depended on fishing for a living. Nearly 100 years later, scientists still disagree over the causes for the biomass fluctuations in the Barents Sea. At the same time, marine research has produced long time series, which can now be analyzed using new methods. This thesis represents an investigation of a number of long time series of Arctic climate indicators and biomasses in the Barents Sea. The purpose of this analysis has been to identify a potential stationary cycle in the biomasses. A stationary cycle in the biomass allows for expanded possibilities for better long-term biomass forecasting.</p><p>The methods are based on general systems theory, analysis of systems dynamics and a wavelet analysis of time series. The wavelet analysis has identified the cycle time and the cycle phase of the dominant cycles in the time series. The phase-relation between the identified cycles contains information abort the dynamic chain of events between climate indicators and the biomasses in the Barents Sea.</p><p>The investigation has identified harmonic and sub-harmonic cycles of the 18.6-year lunar nodal cycle in all analyzed time series. The identified lunar nodal spectrum is explained by a gravity force from the 18.6-year lunar nodal cycle as the First Cause. The energy from the 18.6-year gravity force from the moon introduces a chain of oscillating events. The oscillating gravity introduces a lunar nodal spectrum in the lunar nodal tide and the polar position. A wavelet analysis of time series indicates that movement of the polar position introduces a new lunar nodal spectrum of circulating water in the Arctic Ocean. This circulation water interacts with the 18.6-year lunar nodal tide in the Atlantic Ocean and introduces an oscillation in the extent of Arctic ice, and an oscillation in the inflow of the Atlantic Ocean to the Barents Sea. The lunar nodal spectrum of Atlantic inflow introduces a lunar nodal spectrum in the Barents Sea ecology system. Analysis of the biomass in the Barents Sea shows that long-term growth, reduction and collapse are associated with the phase-relation between the biomass eigen dynamics and the lunar nodal spectrum of Atlantic inflow.</p> / Papers I - VI reprinted with kind permission of Elsevier, www.sciencedirect.com

The Barents Sea contains one of the most productive marine areas in the world. For centuries, Northeast Arctic cod and Norwegian spring spawning herring have been of vital importance for the Norwegian fish export industry and hence economic growth in Norway. It has been common knowledge that the biomass of different Barents Sea species experiences both shortand long-term fluctuations. These fluctuations have been explained by changes in herring cycles and cod cycles, or by the introduction of new fishing equipment, and more. Norwegian marine research began in earnest at the beginning of the 19th century. The main task for researchers was to discover how nature influenced cod stocks and the effects these fluctuations had on the lives of people who depended on fishing for a living. Nearly 100 years later, scientists still disagree over the causes for the biomass fluctuations in the Barents Sea. At the same time, marine research has produced long time series, which can now be analyzed using new methods. This thesis represents an investigation of a number of long time series of Arctic climate indicators and biomasses in the Barents Sea. The purpose of this analysis has been to identify a potential stationary cycle in the biomasses. A stationary cycle in the biomass allows for expanded possibilities for better long-term biomass forecasting. The methods are based on general systems theory, analysis of systems dynamics and a wavelet analysis of time series. The wavelet analysis has identified the cycle time and the cycle phase of the dominant cycles in the time series. The phase-relation between the identified cycles contains information abort the dynamic chain of events between climate indicators and the biomasses in the Barents Sea. The investigation has identified harmonic and sub-harmonic cycles of the 18.6-year lunar nodal cycle in all analyzed time series. The identified lunar nodal spectrum is explained by a gravity force from the 18.6-year lunar nodal cycle as the First Cause. The energy from the 18.6-year gravity force from the moon introduces a chain of oscillating events. The oscillating gravity introduces a lunar nodal spectrum in the lunar nodal tide and the polar position. A wavelet analysis of time series indicates that movement of the polar position introduces a new lunar nodal spectrum of circulating water in the Arctic Ocean. This circulation water interacts with the 18.6-year lunar nodal tide in the Atlantic Ocean and introduces an oscillation in the extent of Arctic ice, and an oscillation in the inflow of the Atlantic Ocean to the Barents Sea. The lunar nodal spectrum of Atlantic inflow introduces a lunar nodal spectrum in the Barents Sea ecology system. Analysis of the biomass in the Barents Sea shows that long-term growth, reduction and collapse are associated with the phase-relation between the biomass eigen dynamics and the lunar nodal spectrum of Atlantic inflow. / Papers I - VI reprinted with kind permission of Elsevier, www.sciencedirect.com

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