IMIS

Generalized and/or withheld information: location information is generalized to 5 x 5 km² Universal Transverse Mercator (UTM) grid cells. Observer name, exact XY-coordinates, toponyms, and photographs are not included in the published dataset, but are known in the source database.
Geographic coverage: Flanders and the Brussels Capital Region. These regions are situated in the north of Belgium and cover an area of 13,522 km² and 162 km² respectively (13,684 km² in total or 45% of the Belgian territory). Flanders is largely covered by agricultural land and urban areas while the Brussels Capital Region is mainly urban. All occurrence data are generalized to grid cells of 5 x 5 km² of the Universal Transverse Mercator (UTM) coordinate system, with the grid codes indicated in the field verbatimCoordinates. The WGS84 centroids of these grid cells are calculated in decimalLatitude/Longitude with a coordinateUncertaintyInMeters of 3,536 meters using Wieczorek et al. 2004.
Taxonomic coverage: The datasets contains 125 naturally occurring fish species (as well as a number of varieties, hybrids and multispecies) recorded in Flanders and the Brussels Capital Region. This includes species that are native, vagrant or migrant. If the observer remarked that the specific individual was introduced by man, then this is recorded in the field establishmentMeans. The class Actinopterygii is best represented in this dataset (108 species), in addition to 13 Chondrichthyes (Cetorhinus maximus, Dasyatis pastinaca, Leucoraja naevus, Mustelus asterias, Mustelus mustelus, Prionace glauca, Raja brachyura, Raja clavata, Raja montagui, Raja radiata, Raja undulata, Scyliorhinus canicula, Scyliorhinus stellaris), three Petromyzontida (Lampetra fluviatilis, Lampetra planeri, Petromyzon marinus) and one Leptocardii (Branchiostoma lanceolatum).
Sampling methods: The observations (species, date, location, observer) were recorded by volunteers (citizen scientists) at http://www.waarnemingen.be. These consist of a mixture of casual observations of living and dead fish, and catches by different methods.
Quality control: Recorded data are constantly verified by fish experts taking the observer’s species knowledge, added photographs and known species list of locations into account. The validation procedure from waarnemingen.be consists of an interactive procedure in which observers can be asked for additional information by a team of validators, after which the validator manually adds a validation status. Records that are not manually validated are additionally checked by an automated validation procedure that takes into account the number of manually validated observations within a specified date and distance range. 16% of the observations in this dataset are supported by a photograph on waarnemingen.be. The validation status is indicated in the field identificationVerificationStatus, the link to the original record in references.
Purpose: Because of their submerged life-cycle, fish observations are classically under-represented in datasets of casual observations. This is also the case in waarnemingen.be. But by making it easy to record any fish species, both marine and freshwater, while making other observations, the website http://www.waarnemingen.be has made it possible to report fish observations more easily and hence stimulated the number of documented casual observations but also catches. However, most amateur fishermen catches and probably all of the commercial fish catches remain unrecorded.
The publication of this dataset was supported by the INBO as part of the Flemish contribution to LifeWatch.