PERSPECTIVE Ecological hypotheses for a historical reconstruction of upper trophic level biomass in

• Main Authors: The Baltic Sea, Brian R. Mackenzie, Jürgen Alheit, Daniel J. Conley, Poul Holm, Christian Kinze
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Øresund; Gadus morhua; Phoca hispida; Phocoena phocoena
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.491.1591; http://www.dfu.dtu.dk/upload/DFU/CV-publikationer/HOEK/ecological_hypotheses.pdf

Abstract: Fish and marine mammal populations in the Baltic Sea and Skagerrak have undergone major fluctuations over the past five centuries. We summarize how these fluctuations may have depended on various forms of predation (e.g., cannibalism, fishing, hunting) and environmental processes. The best-documented long-term fisheries in this region are the herring (Clupea harengus) fisheries near Bohuslän, western Sweden, and in the Øresund. These fisheries have been important since at least the 1200s and appear to be partly climatically driven. However, in the rest of the Baltic, information about fisheries for herring and other fish species is rare until after 1900. During the 20th century, while the Baltic underwent eutrophication, the biomass and landings of three fish species (cod (Gadus morhua), herring, and sprat (Sprattus sprattus)) all increased, whereas the biomass of marine mammals (grey seals (Halichoerus grypus), ringed seals (Phoca hispida), harbour porpoises (Phocoena phocoena)) decreased. The relative roles of exploi-tation, marine mammal predation, and environmental variability (e.g., eutrophication, major inflows of saline water, climate change) on the long-term dynamics of key fish species is not clear and requires increased collaboration among historians, fisheries and marine mammal ecologists, oceanographers, and climatologists. Résumé: Les populations de poissons et de mammifères marins de la mer Baltique et de Skagerrak ont subi d’importantes fluctuations au cours des cinq derniers siècles. On trouvera ici une synthèse qui montre comment ces fluctuations ont pu être reliées à diverses formes de prédation (e.g., cannibalisme, pêche, chasse) et aux processus environnementaux. Les pêches commerciales les mieux connues sur une longue période sont celles de hareng (Clupea harengus) près de Bohuslän dans l’ouest de la Suède et d’Øresund. Ces pêches sont importantes depuis au moins le 13e siècle et elles semblent être au moins en partie sous contrôle climatique. Cependant, les données sur la pêche au