Birds,fish and offal in the North Sea

Estimates that birds take 6–29% of North Sea fish production are examined in the light of revised census results, which on the same basis would suggest that it was 13–48%, and the fishery statistics, which suggest it is more likely to be 0.25–4%. Possible causes for the ten-fold discrepancy include inadequate past allowances for the food contained in the Atlantic inflow to the North Sea and its continued high productivity, the trophic level at which the birds feed, the variety of food which they take, and the movements of both the birds and their prey. It seems likely that the offal discarded by fishermen is more important to birds than the fish that they take, and unlikely that the activity of birds makes much difference to fishermen, but any effect is masked by the slow rate of change of bird populations.