Not Only Environmental Conditions but Also Human Awareness Matters: A Successful Post-Crayfish Plague Reintroduction of the White-Clawed Crayfish (Austropotamobius pallipes) in Northern Italy

Abstract

In Europe, invasive freshwater crayfish are not only changing freshwater ecosystems, but they are also leading to local extinctions of native freshwater crayfish. This is particularly evident for the populations of red swamp crayfish and spiny-cheek crayfish in northern Italy, which are threatening the last and isolated populations of the white-clawed crayfish. Here, we describe the steps that accompanied a successful reintroduction of the white-clawed crayfish in an Italian stream (Park Monte Barro) that, although isolated from other freshwater sites, suffered from an illegal introduction of the spiny-cheek crayfish in 2013. After the removal of presumably all the introduced spiny-cheek crayfish individuals, we started periodical surveys (twice a year) of the stream to confirm the absence of further introductions and to monitor environmental conditions. Prior to the reintroduction of the white-clawed crayfish that started in autumn 2018, we developed an intense dissemination activity to raise awareness of white-clawed crayfish features and importance among landowners surrounding the stream, including those suspected of the introduction of the spiny-cheek crayfish: we organized public meetings and we performed seven direct visits, house to house, to the local people providing information on good practices for white-clawed crayfish conservation. From 2018 to 2020, every autumn, we reintroduced a batch of 3-month-old white-clawed crayfish juveniles, and we developed a program for the monitoring of crayfish growth and density, water quality, and direct landowners’ disturbance of the site. We detected a significant increase of the white-clawed crayfish total length (TL) from the first reintroduction (October 2018) to June 2020. In 2020, crayfish were consistently larger than in the 2019 surveys; some of them were able to breed less than 2 years after the first reintroduction. In 2020, the estimated density of large crayfish reached 0.57 individuals/m2, which is lower than the density observed prior to extinction. We did not detect any case of human disturbance of the site. Our results underline that the reintroduction actions could be more effective when the stakeholders having the greatest potential impact on the species are identified, informed, and involved as primary caretakers of the activities.

Investigation of the first recent crayfish plague outbreak in Ireland and its subsequent spread in the Bruskey River and surrounding areas

“…The mode of spread was downstream but also upstream, probably facilitated by individual movement. Even though the drastic reduction in effective population size may have caused a significant genetic bottleneck, the local population could be restored either by enabling survivors to repopulate the area and/or by careful restocking practices (Manenti et al, 2021;Reynolds et al, 2002Reynolds et al, , 2009Souty-Grosset and Reynolds, 2009), although it may be prudent to continue monitoring for the presence of A. astaci before restocking efforts commence. Maintaining healthy populations of WCC in Ireland is not only important for the preservation of local ecosystems but also because Irish WCC populations have been suggested as potential source stocks for reintroduction in other European areas that are recurrently affected by pathogens and non-indigenous carrier species (Reynolds et al, 2002).…”

Human Dimensions and Visitors’ Perspective in Freshwater Crayfish Conservation: The Case of a Protected Area in Italy

“…The introduction was likely performed with individuals from one of the lakes that surround the park area and host alien crayfish species [34]. Immediately after finding the alien spiny-cheek crayfish, all individuals were removed from the area to start a reintroduction action of A. pallipes five years later [27]. The target species is the threatened white-clawed crayfish, which was present in the small creeks of Monte Barro until 2013, when a direct human introduction of the spinycheek crayfish Faxonius limosus (Rafinesque, 1817) drove the local disappearance of the largest population of the area, possibly due to the spread of the crayfish plague [34].…”

“…On a local scale, integrating social sciences and HDNRM into conservation projects enables investigating stakeholders' attitudes toward protected areas [23,26]). Although often neglected, stakeholders' attitudes may have a strong impact on conservation efforts [27]. The case of freshwater crayfish is in this sense exemplary.…”

“…In these areas, local stakeholders play a central role, and urgent policies are needed to raise awareness and mitigate the impact of human actions. Efforts for freshwater crayfish conservation require interaction with different stakeholders [27] and are expected to provide rapid responses with limited funds. Almost eight million tourists that visit protected areas worldwide every year [30] are key stakeholders in the management of these areas.…”

Soil-Related Predictors for Distribution Modelling of Four European Crayfish Species

“…Modern conservation actions should consider an extensive array of factors that should be monitored and controlled. Among these, the quality of water and surrounding habitats are a priority [41][42][43].…”