Abstract
Biological invasions can have dramatic effects on freshwater ecosystems and introduced crayfish can be particularly impacting. We document crayfish distribution in three large hydrographic basins (Rogue, Umpqua, Willamette/Columbia) in the Pacific Northwest USA. We used occupancy analyses to investigate habitat relationships and evidence for displacement of native Pacifastacus leniusculus (Dana, 1852) by two invaders. We found invasive Procambarus clarkii (Girard, 1852), in 51 of 283 sites and in all three hydrographic basins. We found invasive Orconectes n. neglectus (Faxon, 1885) at 68% of sites in the Rogue basin and provide first documentation of their broad distribution in the Umpqua basin. We found P. clarkii in both lentic and lotic habitats, and it was positively associated with manmade sites. P. leniusculus was positively associated with lotic habitats and negatively related to manmade sites. In the Rogue and Umpqua basins, O. n. neglectus and P. leniusculus were similar in their habitat associations. We did not find a negative relationship in site occupancy between O. n. neglectus and P. leniusculus. Our data suggest that P. clarkii has potential to locally displace P. leniusculus. There is still time for preventive measures to limit the spread of the invasive crayfish in this region.
Highlights
Biological invasions and habitat loss constitute the foremost threats to native species in freshwater ecosystems (Richter et al 1997; Taylor et al 2007)
These traits have been associated with invasion success among crayfish (Larson and Olden 2010), and P. clarkii has been implicated in local displacement of several native crayfish (Gil-Sanchez and Alba-Tercedor 2002; Hanshew and Garcia 2012)
We examined crayfish habitat associations and whether the distribution of native P. leniusculus was related to the distribution of either invader (O. n. neglectus or P. clarkii)
Summary
Biological invasions and habitat loss constitute the foremost threats to native species in freshwater ecosystems (Richter et al 1997; Taylor et al 2007). Invasive crayfish are known to be present in the Northwest, but their introduction history, distribution, and ecological effects are poorly understood (Larson and Olden 2011). Procambarus clarkii is a large, fecund, aggressive species that uses a variety of habitat types (GilSanchez et al 2002; Gherardi 2006; Cruz and Rebelo 2007). These traits have been associated with invasion success among crayfish (Larson and Olden 2010), and P. clarkii has been implicated in local displacement of several native crayfish (Gil-Sanchez and Alba-Tercedor 2002; Hanshew and Garcia 2012). Co-occurrence at the site scale might be more likely between native P. leniusculus and invasive O. n. neglectus because O. n. neglectus is smaller sized, less fecund, and less versatile in habitat use than P. clarkii (Gore and Bryant 1990; Larson and Olden 2010)
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