The influence of sediment type on the distribution of the lesser sandeel, Ammodytes marinus

The lesser sandeel Ammodytes marinus (Raitt, 1934) is an important component of the North Sea ecosystem and the subject of the largest single species fishery in this region. However, little is known about the distribution of this species outside the areas where they are fished. This study examines the physical characteristics of the habitat of A. marinus in an attempt to predict the distribution of this species. The characteristics and topography of sandeel habitat were described from video observations. Data on abundance, sediment characteristics and depth were collected from benthic sampling programmes around the Shetland Isles. These data were used in a general additive model framework (GAM) to examine the relative significance of physical factors in influencing distribution. This analysis found that A. marinus were absent from sediments with a silt/clay content of >10% and densities declined between fractions from 2 to 10%. The apparent dislike for fine sediments was examined further by means of sediment choice experiments. These experiments confirmed the importance of the fine particle fraction in limiting distribution and indicated that sandeels would not be expected to inhabit such areas. Given the constraints of sediment requirements, densities of sandeels in benthic samples appeared to be influenced by water depth.