Report of the Workshop on Gadoid Stocks in the North Sea during the 1960s and 1970s. The Fourth ICES/GLOBEC Backward-Facing Workshop

The Fourth ICES/GLOBEC Backward-Facing Workshop was held in Aberdeen, UK during 11–13 March 1999. The Workshop was commissioned by the ICES Working Group on Cod and Climate Change to examine the possible causes of the ‘gadoid outburst’ in the North Sea during the 1960s and early 1970s. 

The Workshop assembled an inventory of data on climate, physical oceanography, plankton and fisheries during the latter half of the 20th century, and conducted a preliminary analysis of trends and patterns. A set of hypotheses to account for the gadoid outburst in the North Sea was formulated, and each was examined with reference to the available data.

The main conclusions of the Workshop were:

• All four of the major gadoids in the North Sea showed extremes of recruitment in the 1960s and increased catch rates.

• A number of oceanographic characteristics distinguish the 1960s decade from the periods before and after, and appear to be related to the North Atlantic Oscillation (NAO).

• There is some correlation between what happened to the gadoid stocks in the 1960s, the NAO and sea temperatures, but no causal processes could be identified.

• There is a lack of comprehensive understanding of the functioning of the North Sea ecosystem under different climatic conditions and very few systematically collected data on fish early life stages from the relevant periods. Nevertheless, there is a clear holistic relationship between recruitment of cod, in particular, and the NAO.