Spatial Overlap Patterns Between Baltic Larval Cod And Its Prey Obtained From Drift Model Studies

No abstracts are to be cited without prior reference to the author.

Recruitment success of marine fish stocks can to a large degree be related to the feeding success of their early life stages, i.e., larvae and juveniles. Temporal mis-match between the occurrence of larvae and their prey potentially affects the spatial overlap and thus the contact rates between predator and prey. This might have important consequences for growth and survival. We performed a case study investigating the influence of the circulation on the overlap of Baltic cod larvae with their prey. A three-dimensional hydrodynamic model was used to analyse spatio-temporally resolving drift patterns of larval Baltic cod. A coefficient of overlap between modelled larval and idealized prey distributions indicated the probability of predator-prey overlap, dependent on the hatching time of cod larvae. By performing model runs for the years 1979–1998 we have been investigating the intra- and interannual variability in the potential spatial overlap between predator and prey. Assuming uniform prey distributions, we generally found the overlap to decrease since the mid 1980s, however being maximal variable during the 1990s. Seasonally highest overlap occurred in summer and lowest at the end of the cod spawning season. Horizontal variable prey distributions generally resulted in decreased overlap coefficients. Finally, we have related variations in overlap patterns to the variability of Baltic cod recruitment success