Variable fishing mortality and the possible commercial extinction of the eastern Baltic cod

The recent decline in the Baltic cod Gadus morhua L. has been accompanied by an increase in population variability. Small population size, poor recruitment, and high population variability may be factors contributing to their imminent (commercial) extinction. Here we show that variable harvest rate, rather than variable recruitment, is the plausible cause of the increased variance in Baltic cod stock size. This calls for a reconsideration of the role of harvesting as a driving force in exploited populations. The mean exploitation rate, and also the variance, ought to be taken into account in fisheries and other population management.