توالي جانوران كفزي مستقر بر روي چراگاه هاي مصنوعي آب شيرين در ساري

Succession of benthos settled on freshwater Artificial reefs in Sari

density and succession of benthic invertebrate of four Artificial Reefs (cemented rope. brick, wood cercmic) were studied The samples were collected every fifteen clays form March till September 2004. Sampling was clone in the sedimentation pool in Ecological Research Center of Caspian Sea, Sari, Iran. A total ofʹ 2,901 benthic individuals per m^2 of six species were collected that include two species of bivalves, three species of gastropods and one species of crustacean. The biomass of benthos was measured as wet weight. The Total benthos biomass was 975.636 grim. Also the temperature was measured and its relation ship with the density and biomass of invertebrate was Considering the succession of bennas, first, the two algal species of Chara .sp. and Nitella sp. appeared on Artificial Reefs, Finally the gastropod Psuedomnicola sphaerion and then bivalves Dreissena polymorpha and Cerastoderma Lamarckii. The gastropod Valvata piscinalis appeared later. After that, the gastropod Planorbis contortus and finally the shrimp Palaemon elegans were found on artificial reefs. d. polymorpha showed the densest population on reefs with a densityʹ of 593.108 gr/m^2. Results also showed that brick and ceramic treatments attracted more benthic animals (P<0.01). Cemented rope was next and wood was the last in number and biomass of the benthos (P<0.01). The Presence offish (Carassius carassius) and frog (Rana raniʹ) species around the artificial reefs showed that artificial reefs produce food for the bigger predators.