System dynamics of the Barents Sea capelin

The capelin (Mallotus villosus) in the Barents Sea plays a key role in the Arctic food web. The large fluctuations in the biomass of the Barents Sea capelin have been poorly understood and collapses in the biomass have occurred. A system analysis of the capelin stock has identified a state differential equation model and a frequency transfer function model of the stock properties. The results of this research show that the capelin stock dynamics is adapted to the 18.6 year and the 18.6/3=6.2 year lunar nodal tide that influences the temperature in the Barents Sea. An analysis of the capelin time series has identified a 6.2 yr cycle of recruitment, maturity and fish stock growth. An estimated frequency response of a stock-number, life-cycle model has identified a stochastic resonance of about half of the 6.2 yr cycle. The stochastic resonance shows that fluctuation of the stock number is a natural adaptation to the environment and a strategy for optimal growth and survival in the long run. In this stochastic resonance timing between the stock number fluctuation and the 6.2 yr cycle is most important. 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd.