IMIS - Marine Research Groups

The data are compiled from different sources at the INBO, but most of the occurrences were collected through fieldwork for the EU co-funded Interreg project INVEXO. In this project, research was conducted on different methods for the management of American bullfrog populations, an alien invasive species in Belgium. Captured bullfrogs were almost always removed from the environment and humanely killed, while the other occurrences are recorded bycatch, which were released upon catch (see bibliography for detailed descriptions of the methods). Therefore, caution is advised when using these data for trend analysis, distribution range calculation, or other.
Geographic coverage:Flanders, Belgium. Most of the data originate from the province of Antwerp, as this province currently holds the main stronghold of the American bullfrog population.
Taxonomic coverage: The sampling focus for this dataset is American bullfrog (Lithobates catesbeianus (Shaw 1802) syn. Rana catesbeiana Shaw 1802), which represents 25% of the occurrences. The other occurrences are recorded bycatch (native amphibians, fish, non-native crayfish, invertebrates).
Sampling methods: Sampling occurs yearly between April and October. Most of the captures are made with paired fyke nets which are placed at the bottom of ponds and lakes for about 24 hours, but other methods are used as well (indicated in samplingProtocol). With each capture, the number of bullfrogs at each developmental stage is recorded (indicated in lifeStage), as well as bycatch species (native amphibians, fish, non-native crayfish, invertebrates) which were released upon catch. Also recorded are date, location, number of employees involved, and start and end time of the capture event. Captures are conducted for research purposes (management efficiency, determination of population density, etc.) and the active management of bullfrogs. All captured bullfrogs (tadpoles and adults) are humanely killed following international and regional regulation (see bibliography for methods), except for the ponds 13353 to 13362, 13371, and 13372, where the bullfrogs were released for research purposes concerning passive management by introducing native predatory fish. During the INVEXO project (2010 - 2012) those larvae were marked for capture recapture purposes. During the post-INVEXO project (2013) captured (sub)adult bullfrogs received an unique marking on their hind toe webs for the same reason, as well as to receive insight into their movement.
Quality control: Data collection and species identifications were performed by professional scientists or research assistants. The data was encoded in the INBO Recorder6 instance. De data was mapped to Darwin Core using a custom SQL query. All species are validated against the INBO nameserver species lists.
Purpose: The increasing establishment of invasive alien species (IAS) present many challenges for policy makers, managers and researchers. An adequate response to IAS requires accurate and up-to-date information on their distribution. This information can only be provided if IAS data are available and usable by all. American bullfrog is a high profile IAS. Due to its broad global distribution and widespread effects on native biodiversity through various impact mechanisms, American bullfrog is listed as one of the top 100 most invasive alien species in the world by the IUCN (Lowe et al. 2000). The species is suspected to cause substantial ecological damage around large parts of the globe, exerting an additional pressure to already declining amphibian populations. Negative impacts on native biota entail competition, predation and the transmission of pathogens. Subsequently, in Europe, it is listed on the SEBI worst list of invasive non-native species with high impact on biodiversity, as well as the DAISIE list of the worst invasive aliens in Europe. For the same reasons, the species is included in the appendix to the Bern Convention recommendation n° 77 (1999) as a species which has proved to be a strong threat to biological diversity and for which eradication is strongly recommended. Moreover, the EU Wildlife Trade Regulation (338/97) Appendix B prohibits import of the species into the EU since December 1997. It is listed as a species of EU concern sensu the EU Regulation 1143/2014 on the prevention and management of the introduction and spread of IAS. The data in this dataset are useful for scientific purposes such as distribution modeling, as well as early warning and rapid response protocols, but note that bullfrogs (25% of the occurrences) were almost always removed from the environment during the research and eradication campaign.
Issues with the dataset can be reported here.
The publication of this dataset was supported by the INBO as part of the Flemish contribution to LifeWatch.