Evaluating the spatio-temporal impacts of environmental, political and economic changes on the stocks of Northeast Atlantic mackerel and North Sea herring and fisheries

• Main Author: Rybicki, Sandra
• Other Authors: Temming, Axel, Hamon, Katell
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky 2020
• Subjects: bio-economic modelling; herring; mackerel; fisheries; stocks; 590: Tiere (Zoologie); 42.81: Pisces; ddc:590: Atlantik; Northeast Atlantic
• Online Access: http://nbn-resolving.de/urn:nbn:de:gbv:18-ediss-89713; https://ediss.sub.uni-hamburg.de/handle/ediss/8788

The future availability of fisheries resources is highly dependent on international coordination of management decisions, environmental conditions as well as fleet behaviour. Managing straddling and transboundary stocks (i.e. crossing Exclusive Economic Zone boundaries into adjacent international waters) is currently especially difficult due to many changes. Two such stocks, that are highly valuable for European fleets and provide many job opportunities, are the Northeast Atlantic (NEA) mackerel (Scomber scombrus) and North Sea autumn spawning (NSAS) herring (Clupea harengus) stocks. Current conflicts resulting from lack of management coordination or changes in environmental conditions seem, however, to threaten the status of those two stocks. These, in turn, can massively impair the livelihood of European fleets and corresponding employees targeting NEA mackerel and NSAS herring. It is therefore important to evaluate the effects of new management measures and other major impact factors on both the resource availability as well as the fleet behaviour as they are interdependent. Dynamic bio-economic models are now more commonly used as tools for fisheries management. They incorporate anthropogenic as well as natural processes to generate a better understanding of feedback mechanisms between the two systems. This thesis addresses the need to evaluate the impacts of current environmental, economic and political issues on the highly valuable NEA mackerel and NSAS herring stocks and the corresponding fisheries by applying and further developing the FishRent model. It is an age-structured simulation and optimization model that incorporates detailed stock and fleet dynamics on a short- to mid-term time-frame. By identifying the optimal effort allocation under a set of constraints, it can determine the equilibrium state that optimises a certain target variable, i.e. net profit. In the first chapter, the structure of eight pelagic fleets was investigated in order to understand the underlying data and illustrate possible ...