Earth nutation influence on Northeast Arctic cod management

Abstract

Northeast Arctic cod in the Barents Sea is the largest stock of Gadus morhua cod in the world. The cod biomass seems to have stationary cycles related to the Earth's nutation. The present paper suggests that current management strategy has three aspects that may introduce an instability in the biomass. The first is the 6–7 year positive feedback of recruitment in combination with a phase-delay in estimating data and getting the next quota of landings. The second is that the biomass has no stationary biomass reference in the control strategy and the third is the change in the rate of landings each year. Simulations demonstrate that the biomass needs a 15–20 year planning perspective and it is suggested that the spawning-stock biomass level is managed by a feedback control and the fluctuations of landings by a feed-forward control.