Does the prohibition of industrial fishing for sandeels have any impact on local gadoid populations?

Abstract

Industrial fisheries remove large quantities of small fish from the North Sea ecosystem each year. Since these small fish constitute the prey of marine top predators, such activities are considered to pose a potential threat to marine food-web dynamics. The risk to seabird and marine mammal communities has in the past received most attention, but more recently concern has been expressed regarding the possible consequences of industrial fishing for piscivorous fish populations, often the target of fisheries for human consumption. These concerns are addressed in this chapter. A major industrial fishery for sandeels opened on the Wee Bankie in the northwestern North Sea in the early 1990s. Subsequently, in 2000, this fishery was closed in response to concern over its possible impact on local seabird populations. The effect of this closure on the abundance of sandeels in the area – and on local gadoid population abundance, diet, food consumption rates and body condition – are described to examine the effects of the sandeel fishery on these piscivorous, predatory-fish populations. Although closing the sandeel fishery resulted in an immediate increase in the local abundance of sandeels, no beneficial effect on local gadoid populations was detected. Gadoid predators in the area prey almost entirely on 0-group sandeels (fish‘born’ in the current year), while the fishery took predominantly older-aged sandeels. Thus these two consumers appear not to have directly competed for the same resource.