1st Record: Naantali/Finland/Archipelago Sea (2009, Maiju Lehtiniem and Lauri Urho, in ICES Advisory Committee on the Marine Environment 2012, increasing abundance in 2010-2011)
Naantali/Finland/Archipelago Sea (2009, Maiju Lehtiniem and Lauri Urho, in ICES Advisory Committee on the Marine Environment 2012, increasing abundance in 2010-2011); Nantaali-Turku and surrounding islands/Finland/Archipelago Sea (2009-2010, Fowler et al. 2013, increasing range and abundance); Ängsö/Sweden/Archipleago Sea (Gagnon* and Boström 2016, 60°06'31"N; 21°42'45"E, Fucus vesiculosus beds, Zostera marina)
In laboratory experiments using organisms of shallow water Fucus vesiculosus communities, R. harrisii affected the abundances of mussels, amphipods, and isopods, but in field experiments, the abundance of only one snail, Theodoxus fluviatilis, was affected (Forsstrom et al. 2015). The isopod Idptea balthica did recognize the non-native crab as apredator, compared to it's evolved responses to a fish predator, Perca fluviatilis where the isopods sexes and personality types affect vulnerability (Vi-Lenko et al. 2022).
|Ecological Impact||Trophic Cascade|
|On a section of rocky shore in Finland, as the population of Rhithropanopeus harrisii grew, gastropod populations dropped to 1% of their previous population, small crustaceans to 25%, and chironomids disppeared completely. The shore became dominated by mussels (Mytilus trossulus), and filamentous algae, and the growth of Rockweed (Fucus vesiculosus) decreased (Jormalainen et al. 2016).|