Effects of sediment type and light availability on the burying behaviour of small sandeel (Ammodytes tobianus)

This study examines the sediment preferences of small sandeel (Ammodytes tobianus), an elongated forage fish common in marine and brackish environments of northern Europe. Sandeel have a high fidelity for sandy habitats and spend much of their lives buried, as an important part of both their diel behavioural cycles and overwintering behaviour. A series of independent choice laboratory assays were conducted using wild-caught schools of small sandeel, to: (1) determine their preferred substrate composition for burial; (2) identify the upper limits of sediment grain-sizes that may be utilised for burial, and; (3) investigate the effects of light intensity on burial behaviour. Initial experiments found a clear preference for burial within sediments composed of coarse sand and fine gravel (0.5–4.0 mm) but showed at least some utilisation of both coarser and finer sediment compositions. In further trials, burial was found to be almost entirely eliminated in sediments that contained significant gravel components >4.0 mm. Light manipulation experiments also showed that light intensity was an important factor that influences their choice of burial area. This study is the first to experimentally investigate the sediment preferences and grain-size tolerance limits of small sandeel. These results specifically highlight how subtle differences in both sediment composition and light may influence the habitat usage of small sandeel, which may be valuable for understanding their distribution in the wild and to inform future management and conservation for the species.