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Loots, C., Vaz, S., Planque, B., and Koubbi, P. 2010. What controls the spatial distribution of the North Sea plaice spawning population? Confronting ecological hypotheses through a model selection framework. – ICES Journal of Marine Science, 67: 244–257.The spatial dynamics of spawning fish are crucial because they influence the survival rates of eggs and larvae and ultimately impact the reproductive success of populations. The factors that control these dynamics are complex and potentially many, and they interact. A model-selection-based approach was developed to confront various hypotheses of control of the spatial distribution of spawning population of North Sea plaice (Pleuronectes platessa). For each hypothesis or combination thereof, statistical models were constructed. These were then ranked and selected based on their ability to adjust and predict observed spatial distributions. The North Sea plaice population seems to have developed strong attachment to specific spawning sites, where geographic location and population memory are important controlling factors. Temporal changes in spatial distribution patterns appear to be influenced primarily by population size and demography. Variations in hydrographic conditions such as temperature and salinity do not appear to control interannual fluctuations in spatial distribution. This means that, for reproduction, applying conventional habitat models may falsely attribute major controlling effects to environmental conditions. It is concluded that a multiple-hypothesis approach is essential to understanding and predicting the present and future distribution of the North Sea plaice population during its spawning season. [ABSTRACT FROM PUBLISHER]

Long-term regional changes in phytoplankton biomass in the Northeast Atlantic and North Sea are investigated using data from the Continuous Plankton Recorder survey. During the last decade there have been large changes in the long-term variation in phytoplankton biomass in the Northeast Atlantic and North Sea. Most regions, particularly in the North Sea, have shown a considerable increase in phytoplankton biomass while the opposite pattern was seen in the northern oceanic region of the Northeast Atlantic. These different spatial responses show similar patterns of change to the decadal variability in sea surface temperature influenced by the North Atlantic Oscillation index. Two rare oceanographic events and their relationship to the interannual changes in phytoplankton biomass are discussed. The results highlight the importance of maintaining long-term biological monitoring programmes to assess the biological responses to slow oceanic/atmospheric processes and to rare or episodic physical events. [ABSTRACT FROM PUBLISHER]