Proportion of large fish and fishing intensity
Intensification of fishing has led to a decline in the proportion of large fish in the sea.
Trends
The fish size composition in the North Sea is changing. Prior to 1980, large fish accounted for over 25% of the catch weight. This figure has since declined to less than 10%.
The shift in the size composition reflects changes in the age structure of the fish population. Few fish are currently able to survive long enough to reproduce, and this is putting the production of sufficient young fish at risk.
Technical note
The graph is based on standardised surveys of stocks conducted annually from research vessels since 1969 in the southeastern North Sea in September: the Sole Net Surveys. It shows the percentage of the total catch made up of large fish (longer than 25 cm) per year. The five-year running mean is also shown.
References
- Heessen, H.J.L., H.C. Welleman, N. Daan, A.C. Smaal en G.J. Piet (2001). Bijdrage RIVO aan Natuurcompendium 2001. Nederlands Instituut voor Visserijonderzoek RIVO. Intern rapport C058/01. IJmuiden.
