IMIS

Here it is published as a standardized Darwin Core Archive and includes for each species: the scientific name, higher taxonomy, stable taxon ID (in the taxon core), the year of first introduction and/or last assessment in Flanders (given as a year or year range in the event date in the distribution extension), coarse habitat information (in the species profile extension) and the native range(s), pathway(s) of introduction and degree of establishment in Flanders (in the description extension). Issues with the dataset can be reported at https://github.com/trias-project/alien-scheldt-checklist
We have released this dataset to the public domain under a Creative Commons Zero waiver. We would appreciate it if you follow the INBO norms for data use (https://www.inbo.be/en/norms-data-use) when using the data. If you have any questions regarding this dataset, don't hesitate to contact us via the contact information provided in the metadata or via opendata@inbo.be.
This dataset was published as open data for the TrIAS project (Tracking Invasive Alien Species http://trias-project.be, Vanderhoeven et al. 2017), with technical support provided by the Research Institute for Nature and Forest (INBO). It is selected as one of the authoritative sources for the compilation of a unified and reproducible checklist of alien species in Belgium.
Prior to 2008, sampling was conducted every third year at fixed intertidal and subtidal stations in an increasing quantity of sites: from 51 sampling sites in 1999 up to 75 in 2005. At each sampling site, 3 core samples (diameter: 3.5 cm; depth: 10 cm) were collected. In case of subtidal samples, these were obtained from a Reineck boxcorer (diameter: 15 cm; depth: 10 cm). Sampler size was chosen to reduce highly laborious sorting effort of samples with high densities of oligochaetes (occasionally more than 1 106 individuals m-²). Sediment samples were stored in 4% formaldehyde. In the laboratory, samples were sieved in two steps over mesh sizes of 250 μm and 1000 μm. Benthic invertebrates were sorted, identified to species level, and counted. Since 2008, samples have been collected each year, following a stratified random sampling design; 212 stations are stratified by salinity zone, subtidal depth, and intertidal elevation. Two core samples (diameter: 4.5 cm; depth: 15cm) were collected at each station, fixed in 4% formaldehyde, and taken to the laboratory. These were sieved over mesh sizes of 500 μm and 1000 μm and subsequently treated as described for the samples collected prior to 2008. Since 2013 hyperbenthic monitoring occurs at 6 fixed stations; five locations along the Scheldt and one along its major tributary the Rupel. Other locations are sporadically sampled. For regular monitoring a bongonet (diameter, mesh 1mm) is pulled back and forth by 2 persons at low tide over 100m (total distance 200m). As part of projects, occasional samplings occur with the bongo net or less frequent using a benthic sledge (width 1m, heigh 50cm). Samples are always taken along the shoreline at low tide, with the exception of a series of bongo net samples taken from a boat near the surface in the navigation channel. All samples were fully sorted and all species identified to the lowest level possible. Very large samples (1000s of specimens) were subsampled (usually 1/8).