Causes and consequences of crayfish extinction: Stream connectivity, habitat changes, alien species and ecosystem services

Abstract

Given the ongoing decline of many species, it is important to perform multifactorial analyses of conservation status and to assess the effects of species extinction on ecosystem services. In this study, we used long‐term surveys to assess the influence of habitat change, landscape alteration and invasive species on extinction risk of the native crayfish Austropotamobius pallipes. We reviewed the existing literature to assess which ecosystem services are threatened by local extinction of A. pallipes and replacement with alien crayfish. We sampled 196 streams and wetlands in northern Italy. Of these, 117 received multiple surveys over a 13‐year period (2004–2017), thus allowing accurate measurement of extinction rate. Thirty‐four percent of A. pallipes populations underwent extinction between 2004 and 2017. The occurrence of alien crayfish in the catchment basin and urban growth in the landscape surrounding streams were associated with A. pallipes extinction. The probability of persistence was significantly higher in populations close to stream springs and with physical barriers (especially waterfalls) separating them from basins with alien crayfish. Extinction of native crayfish alters community structure and impairs regulating services such as detrital breakdown and pest regulation. Replacement by alien crayfish (Procambarus clarkii and Faxonius limosus) also threatens supporting and regulating services by altering nutrient cycling, food webs, sediments and erosion. The implementation of management practices that control river connectivity using selective barriers is needed to prevent further local extinction of native species. Integrating information on extinction with knowledge of impacts on ecosystem services is essential in developing more effective conservation policies.

Invasive crayfish does not influence spawning microhabitat selection of brown frogs

“…Particular attention was paid to the occurrence of small young individuals. Additional surveys were performed in the same sites during the late spring-middle summer of 2017 and 2019 and confirmed the absence of alien crayfish detection in the sites considered as non-invaded during this study (Manenti et al, 2019b). For only one pond we don't have data of relative abundance of crayfish.…”

“…The invasive crayfish is widespread in the study area (Manenti et al, 2020;Manenti et al, 2019b) and is likely to attain high density, making eradication programs almost impossible. Under these circumstances, it is essential to identify the processes that can allow long-term persistence of native species, such as behavioural changes or the selection of specific microhabitats.…”

“…There are many reported cases of dramatic effects of alien species introduction on native species, which range from behavioural shifts of native species (Tiberti & Von Hardenberg, 2012;Winandy & Denoël, 2013) to cascading effects on entire ecosystems, and can lead to the extirpation of entire species or communities (Arribas, Díaz-Paniagua & Gomez-Mestre, 2014;Bonelli, Manenti & Scaccini, 2017). Semi-aquatic organisms like amphibians can play important roles for nutrient exchanges between aquatic and terrestrial habitats ( Barzaghi et al, 2017;Gibbons et al, 2006), thus invasive crayfish is expected to deeply affect the biotic community of both lentic and lotic environments (Ficetola et al, 2012;Ficetola et al, 2011b;Gherardi & Acquistapace, 2007;Manenti et al, 2019b;Shin-ichiro et al, 2009). If the breeding microhabitat selected by adult amphibians is important for their breeding success, we expect a modulation of habitat choice in response to the presence of IAS.…”

“…To verify the occurrence of the red swamp crayfish and to measure the relative abundance of crayfishes in ponds active during the breeding period, we performed one visual encounter survey during night-time to maximize the detection probability of the crayfish. Recent studies showed that during nocturnal surveys the per-visit detection probability is very high (>95%; Manenti et al, 2019b). Surveys were performed using night lamps along the whole perimeter of the ponds and lightening the inner sectors as much as possible.…”

“…The red swamp crayfish Procambarus clarkii is among the IAS with the strongest impact both in Europe and on a global scale (Nentwig et al, 2018). This crayfish is a generalist feeder (Alcorlo, Geiger & Otero, 2004;Whitledge & Rabeni, 1997), and its global spread affects a growing number of freshwater communities worldwide (Cruz et al, 2008;Ficetola et al, 2011b;Manenti et al, 2019b;Ramamonjisoa, Rakotonoely & Natuhara, 2018;Vilà et al, 2010). P. clarkii preys on tadpoles of several amphibian species (Cruz et al, 2008); in northern Italy crayfish predation is a major cause of local extinctions and tadpole abundances reduction (Ficetola et al, 2011b).…”