Abstract
The invasive alien crayfish Pacifastacus leniusculus is considered harmful to freshwater pearl mussels Margaritifera laevis and M. togakushiensis. It also often colonises mussel habitats in Japan. In order to test the negative effects of alien crayfish on mussels, we evaluated the predation impact of signal crayfish on freshwater pearl mussels in vitro. We tested the relationship between the survival/injury rates of mussels and crayfish predation with respect to different sizes of mussels (four classes based on shell length: 10, 30, 50 and 70 mm). Crayfish selectively fed on the flesh of the 10-mm size class mussels after breaking their shells. The shell margins of mussels in all size classes were injured by crayfish. Results also showed that crayfish particularly injured the 50-mm size class of mussels. This observation could be attributed to this mussel size being the most suitable shell size (29.56–37.73 mm in carapace length) that the crayfish can effectively hold. This study shows that the presence of invasive crayfish reduces freshwater pearl mussel populations by damaging the shell margins and/or killing the mussels. This negative impact of invasive crayfish not only decreases the mussel population but could also limit mussel recruitment, growth and reproduction.
Highlights
The invasive alien crayfish Pacifastacus leniusculus is considered harmful to freshwater pearl mussels Margaritifera laevis and M. togakushiensis
All the mussels in the smallest size class survived in the Control experiments, and the survival rates of the smallest mussels in the Control and Crayfish trials were not significantly different
All the mussels in the other size classes (SL: 30.29–37.54, 50.51–58.41 and 70.65–76.39 mm) survived in the Crayfish and Control trials indicating that the survival rate was not significantly different in the Crayfish and Control trials for these size classes
Summary
The invasive alien crayfish Pacifastacus leniusculus is considered harmful to freshwater pearl mussels Margaritifera laevis and M. togakushiensis. It often colonises mussel habitats in Japan. Akiyama Environmental Research and Management Center, Hiroshima University, 1-5-3 Kagamiyama, Higashi-hiroshima, Hiroshima 739-8513, Japan mussel populations by damaging the shell margins and/or killing the mussels This negative impact of invasive crayfish decreases the mussel population but could limit mussel recruitment, growth and reproduction. Given its detrimental impacts on native biodiversity and ecosystem functions, the signal crayfish was designated as an Invasive Alien Species (IAS) by the Ministry of the Environment of Japan on 1. Crayfish dramatically affect the structure and function of ecosystems by predating macrophytes and aquatic invertebrates (Nishikawa et al, 2009)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
