Visherintroductie - Reintroduction of the fishes chub, dace, burbot, and brown trout in Flanders, Belgium is a species occurrence dataset published by the Research Institute for Nature and Forest (INBO). The dataset contains over 3,300 fish occurrences sampled between 2008 and 2011 from 18 watercourses. The dataset includes 20 fish species. The data are collected to evaluate the success of the reintroduction of the fishes chub, dace, burbot and brown trout in Flanders. The captured numbers were compared with the expected numbers, which were determined in previous studies based on habitat suitability models. The dataset also includes the length and mass of the caught fishes. Issues with the dataset can be reported at https://github.com/LifeWatchINBO/data-publication/tree/master/datasets/visherintroductie-occurrences To allow anyone to use this dataset, we have released the data to the public domain under a Creative Commons Zero waiver (http://creativecommons.org/publicdomain/zero/1.0/). We would appreciate it however if you read and follow these norms for data use (http://www.inbo.be/en/norms-for-data-use) and provide a link to the original dataset (https://doi.org/10.15468/dlglrp) whenever possible. If you use these data for a scientific paper, please cite the dataset following the applicable citation norms and/or consider us for co-authorship. We are always interested to know how you have used or visualized the data, or to provide more information, so please contact us via the contact information provided in the metadata, opendata@inbo.be or https://twitter.com/LifeWatchINBO.