 Additionally, in 1969 a freshwater jellyfish ("Craspedacusta sowerbii") was documented in the lake, a continental species then new to Sweden but not found in the lake since.Fishes natural to Långsjön include perch, northern pike, roach, rudd, carp bream, crucian carp, tench, and ruffe; extraneous species are common carp and mirror carp.Pike and zander are planted-out carnivorous species while roach and crucian carp have been decimated by trawling.