Abstract
We aim to develop key elements of an operational ecosystem model framework. The model system includes ocean physics, the timing of the spring bloom from Sverdrup assumptions, and predicted egg-production of zooplankton. This culminates in a spatio-temporal map of the value of an egg in terms of early life-stage growth and survival, which is combined with optimal life-history models and population modelling to predict spawning site use in NEA cod and NSS herring. One key asset for the project is a new version of the regional ocean model system (ROMS) developed by the IMR. The domain included in this model allows a fine-scaled resolution of the coastal current along the complete range of the Norwegian coast and opens new doors to the exploration of larval drift and egg fitness from all potential spawning sites. Another new and novel advancement is the development of trait-based phytoplankton model of the spring bloom. The approach taken is inspired from recent work by Mick Follows and his group at MIT, and we ask for a one year visit by the project leader to MIT, Boston to develop such models. The next component of the operational framework is to apply the model of Calanus finmarchicus, the main food item for larval fish, developed by Geir Huse and colleagues at IMR. The output from this modelling is a spatial, annual and seasonal map of suitable food availability for larval fish along the coast. We then bring these pieces together to model the fate of an egg spawned at different times and locations along the coast, which determines the fitness of the egg. Finally, the fitness of eggs can be thought of as the payoff-function of the migration cost in a life-history energy trade-off in both cod and herring. The egg-fitness will be fed into existing models of energy usage in parental fish, yielding an optimal state-dependent migration investment which can be placed in a population dynamics context interacting with fisheries practices.
Norway