Distribution of Palaemonetes varians (Leach) (Crustacea, Decapoda) in relation to biotope and other caridean shrimps in brackish waters of southern Norway and southwestern Sweden

Abstract

Palaemonetes varians has been recorded at 11 localities in southern Norway and one locality in Bohuslän, Sweden. Its habitat is brackish water lakes and shallow, coastal lagoons of variable salinity (0.9–25.3). In Oslofjord, lagoons are rare, and P. varians was only found at one locality, Stokke in the county of Vestfold, on the western side of the fjord. No specimens were recorded along the coast north of Strömstad, Bohuslän, which is far north of previous records in Sweden. The occurrence of P. varians in southern Norway seems to be quite isolated from its main distribution in Europe. In high and medium saline (salinity > 5) biotopes, P. varians often occurred with Palaemon elegans and/or P. adspersus, which are common in more open and turbulent biotopes along the coast. In shared localities, P. varians seemed to be competitively displaced by the larger Palaemon species into large stands of telmatophytic vegetation, and few were found in open water. At low salinities (< 5), as the only caridean present, P. varians occurred in great numbers everywhere in large, brackish water lakes and lagoons. Crangon crangon was found at similarly low salinities, but not in lagoons.