Summary of an update of the Mori-Butterworth (2006) model of the krill-predator dynamics of the Antarctic ecosystem
The Mori-Butterworth (2006) model of the krill-predator dynamics of the Antarctic ecosystem is refined in Moosa (2017). Updates to and the revision of abundance and trend information are summarized. Key features of the updated and refined model are the inclusion of a depensatory effect for the Antarctic fur seals in the krill and predator dynamics, and the imposition of bounds on K_a (the carrying capacity of krill in Region a, in the absence of its predators); these lead to a better fit to the data overall. A particular difference in results compared to those from the Mori-Butterworth model is more oscillatory behaviour in the trajectories for krill and some of its main predators. This likely results from the different approach to modelling natural mortality for krill (which decreases the residual mortality remaining after taking account of consumption by the main predators) and warrants further investigation. That may in turn resolve a key mismatch in the model which predicts minke whale oscillations in the Indo-Pacific region to be out of phase with results from a SCAA assessment of these whales. A number of other areas for suggested future research are listed.