A Comparison of Fish Size-Composition in the North Sea and on Georges Bank

Aggregated length distributions of all fish species combined may be obtained from groundfish surveys conducted by the UK and the USA for the North Sea and Georges Bank respectively. In both areas, the aggregate logarithmic numbers at length decline linearly over the fully selected size range. Comparison of these distributions through time and between areas indicates that slope varies considerably between areas but much less through time within an area. Such observed changes are consistent with the slope of the line being a broad indicator of the exploitation regime, the more heavily exploited North Sea having a steeper decline with size than that of Georges Bank. The slopes of distributions on Georges Bank show more gradual declines in years after management regimes were imposed. It seems possible, therefore, that aggregate size distribution may be a characteristic property of exploited fisheries systems — perhaps an emergent property.