Several thousand planned wind turbine foundations will substantially increase the amount of habitat available for hard-bottom associated mobile demersal megafauna (MDM) in the German Bight (North Sea). To assess the effect of the large-scale habitat creation on MDM-stocks, the foundations (tripods and jackets) of the small-scale alpha ventus wind farm were systematically scrutinized by diving. Two years after construction, hard-bottom species already reached 100 fold higher abundances at the foundations than at autochthonous soft sediments. Large concentrations of pouting (Trisopterus luscus) and the Atlantic horse mackerel (Trachurus trachurus) were detected at the foundations. The brown crab (Cancer pagurus) reached abundances of 2,300 individuals at single foundations, whereas it reached only 29 individuals in the reference areas. The uppermost parts of the foundation structures were densely and exclusively colonised by young C. pagurus – they potentially function as nursery grounds. The stocks of predatory hard bottom species could multiply with the installation of numerous offshore wind farm foundations in the North Sea. The settlement of MDM at the foundations of wind farms should be considered when assessing offshore wind farm reef effects and possible environmental impacts. The effects of alpha ventus on pelagic fish were investigated by hydroacoustic surveys, by sampling with net catches and by fish stomach content analysis. A relative decline in abundance of pelagic fish in alpha ventus during the construction phase suggests scaring effects on fish caused by pile driving and other construction related activities. Stomach content analysis shows that hard substrate associated organisms were an insignificant food component of Atlantic mackerel (Scomber scombrus) and T. trachurus captured within the alpha ventus wind farm. Mackerels caught within the wind farm showed a significantly reduced degree of stomach fullness compared to mackerels caught outside the wind farm, suggesting disturbed food gathering behaviour or differences in food composition and distribution within the wind farm area.