1. a Department of Zoology , Vilnius University , Čiurlionio 21/27, LT-03101 , Vilnius , Lithuania , correspondence: Institute of Ecology of Vilnius University, Akademijos 2, LT-08412 Vilnius-21, Lithuania
2. b Coastal Research and Planning Institute , Klaipėda University , Manto 84, LT-92294 , Klaipėda , Lithuania