Cryptogenic and Non-Indigenous (NIS) in Northern Portuguese recreational marinas under different salinity conditions

The number of recreational marinas has increased in recent years due to the growing demand for leisure boating. Recreational marinas are key points for the introduction of non-indigenous species (NIS). However, there is a scarce knowledge on the influence of environmental features on NIS fouling assemblages, especially regarding different salinity conditions. This dataset contains information on the abundance (in terms of density of individuals) of cryptogenic and NIS associated with floating pontoons of six Northern Portuguese marinas in under two different salinity conditions: marine vs brackish.