Module 5. Trophodynamic system integration

Participants:
Svein Sundby (IMR)(Module leader), Lars Asplin (IMR), Øyvind Fiksen (IFM, UoB), Olav Kjesbu (IMR), Harald Loeng (IMR), Webjørn Melle (IMR), Einar Svendsen (IMR)

Objective:
Develop a trophodynamic model system that integrates the models described above to simulate growth and recruitment of Barents Sea fish stocks. The trophodynamic model system will form the basis for sensitivity analysis to explore quantitatively the effects of the range of physical and biological parameters and processes of importance to the general problem of fish recruitment.

The ultimate goal of the trophodynamic modelling is a fully linked model system developed from first principles from phytoplankton production to 0-group fish. In the complete version this goal is beyond reach within the 4-yrs project period. This is because we at present do not know all key processes of relevance for trophic transfer, and consequently have not sufficient knowledge for expressing all relations in a mechanistic and mathematical framework. Particularly, development of an individual-based copepods model that realistically simulates growth and stage development based on egg production, physics and phytoplankton production is needed. We expect, however, that we will, together with other NFR-funded projects, advance considerably towards this goal before the end of the ECOBE project. In addition, we start to see international efforts in making such integrations (Hermann et al. 2001; Hinckley et al. 2001). Meanwhile, we will utilise our best gained knowledge in the region on ocean climate relations, water mass advection, copepods life stages and production in relation to physical parameters, zooplankton time series and statistics, in addition to present state-of-the-art zooplankton models, to parameterise food abundance into the models of fish larval transport, growth and survival. For example, we have gained recent knowledge about the relation between the NAO index and the abundance of Calanus finmarchicus in the proper basin of the Norwegian Sea (Melle 2001). The system integration in ECOBE will, therefore, partly rely on bio-physical models and partly on physical-biological correlation based on field measurements and time series. The system integration is a major focus and challenge of the much broader AMØBE project. In the present ECOBE project we aim towards a more fully trophodynamic interlinking than in the broader AMØBE project, since present state of mechanistic knowledge on lower trophodynamics is better explored than at higher trophic levels.

From the developed model system of trophodynamic integration we will run model scenarios and sensitivity analyses on the range of variations in biological and physical parameters and processes to quantitatively explore the effects of various recruitment hypotheses, such as the match-mismatch hypothesis (Cushing 1974; Ellertsen et al. 1989), the effects of turbulence (Rothschild and Osborn 1988; Sundby and Fossum 1990), the effects of light conditions (Fiksen et al. 1998), the bigger-is-better hypothesis (Leggett and Deblois 1995) and the composite effects of temperature and copepods advection (Sundby 2000).

In addition to the trophodynamic system integration described above, the Module 5 budget includes the expenses for communication and cross-cutting activities and the secretariat for the ECOBE project.