Modelling cannibalism and inter-species predation for Cape hake Merluccius capensis and M. paradoxus: an update to MARAM IWS/DEC13/Ecofish/P10.

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University of Cape Town

An update is given to the hake predation model presented in MARAM IWS/DEC13/Ecofish/P10. Several modifications have been made to the earlier model, following recommendations by the panel at IWS DEC13 and interim model development. The current model, while still troubled with some conflicts, shows promise as a reasonable base case model that takes predation and cannibalism into account. Results are given for three cases that give increasing weight to various diet data likelihood components. It was found that if the model fits well to the trend data and proportion of hake in diet, the fit to daily ration is poor. On the other hand, if the model fits well to the daily ration and proportion of hake in diet data, the consequential loss is a worse fit to the trend data. This document presents some of the diet data that are available, the methodology for the current model, and a selection of results for the three cases, as well as a list of suggested discussion points.