A second population of Cabomba caroliniana Gray (Cabombaceae) in Belgium with options for its eradication

Abstract

This is the first attempt to outline the occurrence of selected invasive alien vertebrates in Greece, since up to now, there are no "official" or scientific reports except from sporadic sightings and anecdotal stories. Records on the occurrence of: Lithobates catesbeianus, Trachemys scripta (T. s. elegans and T. s. scripta), Neovison vison, Myocastor coypus, Nyctereutes procyonoides and Ondatra zibethicus were requested through a pan-Hellenic survey. According to the results, the coypu (Myocastor coypus) appears to be the most widely distributed of all species, having conquered practically all wetlands of Western and Central Greece with populations exceeding, in most cases, 20 individuals each. On the contrary, there is merely one unconfirmed record of the raccoon dog (Nyctereutes procyonoides) while there were no sightings at all for the muskrat (Ondatra zibethicus). The American mink (Neovison vison) was recorded in the northwestern part of Greece. Regarding the alien herpetofauna, the bullfrog (Lithobates catesbeianus) seems to be still confined in Crete where it was originally introduced, while the red-eared slider (Trachemys scripta) appears mostly in Crete, Attiki prefecture, and a few more places, showing most probably an underestimated distribution.

Guidance for drafting best management practices for invasive alien species

“…An example of this is the best practice for the management of the pumpkinseed sunfish (van Delft et al, 2013) or the decision support framework for management of Carolina fanwort Cabomba caroliniana (Scheers et al 2016); these use relatively simple decision trees to allow users to quickly work through the research and control regulations, as well as introducing a 'management key' that can serve as a guideline if a decision has to be made about whether to take control measures. This key includes prevention, migration limitation and control options (Figure 3).…”

Cabomba caroliniana Gray (Cabombaceae) invades major waterways in Belgium

“…In Belgium, C. caroliniana was reported only twice, so far, and only from hydrologically isolated, stagnant water sites of limited size where it was probably introduced from aquarium culture. The first record (Denys et al, 2000(Denys et al, , 2003Verloove, 2002) was in an derelict fishpond near Holsbeek, Province Vlaams-Brabant, where a stable population occurred from 1998 up to 2006 when it disappeared following restocking with fish and development of turbid conditions (Scheers et al, 2016). A second occurrence was noted in 2013 near Sint-Pauwels, province Oost-Vlaanderen.…”

“…A second occurrence was noted in 2013 near Sint-Pauwels, province Oost-Vlaanderen. Here, C. caroliniana was the dominant hydrophyte in a ditch amidst a residential area (Scheers et al, 2016). Considerable effort was made to eradicate the species at this site, including drawdown and mechanical removal in the summer of 2018 followed by manual removal of remaining fragments and new shoots, at a total expense of 40 k€.…”

“…Considering the widespread and locally problematic occurrence of C. caroliniana in The Netherlands (Matthews et al, 2013), the small number of records in Belgium À only two sites in almost 15 yearsup to the last few years is striking. Based on the isolated character of these colonies, one of which disappeared without targeted control measures, the more scattered occurrence of potential habitat and the generally much lower hydrological connectivity of water bodies compared to The Netherlands, Scheers et al (2016) considered the risk of C. caroliniana becoming widespread in Belgium as rather low. This was prior to any observations in waterways, however, and only considered punctual, unrelated introductions.…”

“…Because C. caroliniana has now entered navigable waterways of considerable size and economic importance, its complete eradication in lower Belgium seems to have become very unlikely. None of the more efficient and commonly used eradication methods for invasive macrophytes (Drolet et al, 2014) or C. caroliniana in particular (Scheers et al, 2016;Hussner et al, 2017) appear suited for these conditions. A dedicated survey for C. caroliniana, including less easily accessible parts and areas adjacent to the canal, is necessary to guide any decision on managing this invasive species and to evaluate options for limiting its spread or mitigating associated risk or impact.…”