FishBase held its annual Symposium in Stockholm yesterday focusing on invasive species. A number of invited researchers shared their expertise and knowledge of past, current and future invasive species in European waters and possible management actions.
An invasive species is described according the International Union for Conservation of Nature (IUCN) as “animals, plants or other organisms introduced by man into places out of their natural range of distribution, where they become established and disperse, generating a negative impact on the local ecosystem and species.”
Christine Casal from FishBase gave an interesting and inspiring presentation on how scientist, managers and NGOs can use FishBase for risk assessments of invasive species. FishBase is continuously being updated with new information and are currently developing a matrix for invasive species risk assessments.
The Danish researcher Peter Rask Moller pointed out that the Round goby, one of the few marine invasive species in the Baltic Sea, have been shown to spread its distribution about 30 km per year. This would mean that by next year the round goby population would be expected to have “moved” as far south as waters close to Copenhagen. This could potentially pose a problem to the commercial shrimp fishermen as the round goby has the potential to deplete shrimp stocks. Rask Moller pointed to an additional possible negative effect a southward expansion of the round may have on the Baltic Sea marine ecosystem. There are indications that the round goby dig up eelgrass meadows, this would pose additional pressure on already stressed fish populations in the Baltic Sea as eelgrass meadows play an important role as nursing ground for many species.
All speakers talked about different management options of how to control invasive species. The overall take-home message on how we best can manage invasive species once they have established themselves is to lower commercial fishing pressure as a high fishing pressure may trigger invasive species populations. A lowered fishing pressure on commercial fish stocks would most probably result in a decrease in population size of invasive species.