بررسي مطلوبيت زيستگاهي دو كفه اي قو (Anodonta cygnea, Linnaeus, 1758) به عنوان يك گونه شاخص زيستي در بخش هاي مختلف تالاب انزلي

دوﻛﻔﻪ اي ﻗﻮ)Anodonta cygnea( ﻳﻚ ﮔﻮﻧﻪ ﺑﺰرگ آب ﺷﻴﺮﻳﻦ اﺳﺖ ﻛﻪ ﺑﻪ ﻧﺎم دوﻛﻔﻪ اي رودﺧﺎﻧﻪ اي ﻫﻢ ﺷﻨﺎﺧﺘﻪ ﺷﺪه اﺳﺖ. ﺑﺮاي ﺑﺮرﺳﻲ ﻣﻄﻠﻮﺑﻴﺖ زﻳﺴﺘﮕﺎﻫﻲ A. cygnea، ﺷﺶ اﻳﺴﺘﮕﺎه از ﻗﺴﻤﺖ ﻫﺎي ﻣﺨﺘﻠﻒ ﺗﺎﻻب اﻧﺰﻟﻲ اﻧﺘﺨﺎب ﺷﺪ. در ﻫﺮ اﻳﺴﺘﮕﺎه ﻣﺠﻤﻮﻋﻪ اي از ﻣﺘﻐﻴﺮﻫﺎ در ارﺗﺒﺎط ﺑﺎ ﺧﺼﻮﺻﻴﺎت ﻛﻴﻔﻲ آب و رﻳﺨﺖ ﺷﻨﺎﺳﻲ ﻣﺤﻴﻂ ﺑﻄﻮر ﻫﻤﺰﻣﺎن ﺑﺎ 36 ﻧﻤﻮﻧﻪ ﺣﻀﻮر و 36 ﻧﻤﻮﻧﻪ ﻋﺪم ﺣﻀﻮر اﻓﺮاد ﮔﻮﻧﻪ ﺑﻪ ﺻﻮرت ﻣﺎﻫﺎﻧﻪ در ﻃﻮل ﻳﻚ ﺳﺎل )1396-1397 اﻧﺪازه ﮔﻴﺮي ﺷﺪ. ﺑﺮاﺳﺎس ﻧﺘﺎﻳﺞ آزﻣﻮن ﻣﻦ وﻳﺘﻨﻲ اﺧﺘﻼف ﻣﻌﻨﻲ داري در ﺧﺼﻮص ﺣﻀﻮر و ﻋﺪم ﺣﻀﻮر دوﻛﻔﻪ اي ﻣﻮرد ﻧﻈﺮ ﺑﺎ ﺑﻴﺸﺘﺮ ﻣﺘﻐﻴﺮﻫﺎ وﺟﻮد داﺷﺖ )0/05 P <( ﺑﺮاي ﻓﺴﻔﺎت و ﻣﻮاد ﺟﺎﻣﺪ ﻣﻌﻠﻖ و ﺑﺮاي ﺑﻘﻴﻪ ﻋﺎﻣﻞ ﻫﺎ )0/01 P <(. ﺗﻨﻬﺎ اﺳﺘﺜﻨﺎ دراﻳﻦ ﺧﺼﻮص در ﻣﻮرد ﻣﺘﻐﻴﺮﻫﺎي درﺟﻪ ﺣﺮارت آب وﻫﻮا ﻣﺸﺎﻫﺪه ﺷﺪ ﺑﻄﻮرﻳﻜﻪ ﺑﺮاﺳﺎس ﻧﺘﺎﻳﺞ آزﻣﻮن، ﻫﻴﭻ ارﺗﺒﺎط ﻣﻌﻨﻲ داري در ﻣﻮرد ﺣﻀﻮر و ﻋﺪم ﺣﻀﻮر اﻓﺮاد ﺑﺎ اﻳﻦ دو ﻣﺘﻐﻴﺮ ﻣﺸﺎﻫﺪه ﻧﺸﺪه اﺳﺖ. ﺑﺮاﺳﺎس ﻧﺘﺎﻳﺞ ﻣﺪل ﺧﻄﻲ ﺗﻌﻤﻴﻢ ﻳﺎﻓﺘﻪ، اﻓﺰاﻳﺶ ﻋﻮاﻣﻠﻲ ﻣﺜﻞ ﻋﻤﻖ آب، ﺳﺮﻋﺖ ﺟﺮﻳﺎن آب، ﻛﺪورت آب،ﻫﺪاﻳﺖ اﻟﻜﺘﺮﻳﻜﻲ، ارﺗﻮ ﻓﺴﻔﺎت و ﻧﻴﺘﺮات ﻣﻤﻜﻦ اﺳﺖ ﺑﺎﻋﺚ ﻛﺎﻫﺶ اﺣﺘﻤﺎل ﺣﻀﻮر اﻓﺮاد ﮔﻮﻧﻪ )0/01 P <( و ﺑﺮﻋﻜﺲ اﻓﺰاﻳﺶ ﻏﻠﻈﺖ اﻛﺴﻴﮋن ﻣﺤﻠﻮل و ﺳﺨﺘﻲ ﻛﻞ ﻣﻤﻜﻦ اﺳﺖ ﺑﺎﻋﺚ اﻓﺰاﻳﺶ اﺣﺘﻤﺎل ﺣﻀﻮر ﻣﻮﺟﻮد در ﺗﺎﻻب ﺷﻮد )0/01 P <(. ﺑﺮاﺳﺎس ﻧﺘﺎﻳﺞ ﻣﺪل ﺧﻄﻲ ﺗﻌﻤﻴﻢ ﻳﺎﻓﺘﻪ ﻫﻴﭽﮕﻮﻧﻪ ارﺗﺒﺎط ﻣﻌﻨﻲ دار آﻣﺎري ﺑﻴﻦ ﺣﻀﻮر و ﻋﺪم ﺣﻀﻮر ﮔﻮﻧﻪ ﺑﺎ دﻣﺎي آب ﺑﺪﺳﺖ ﻧﻴﺎﻣﺪه اﺳﺖ.

The swan mussel, Anodonta cygnea, is a large species of freshwater mussel, an aquatic bivalve mollusc known as the river mussels. In this study, six sampling sites were selected from different parts of the Anzali wetland to examine the habitat suitability of A. cygnea. At each site, a set of variables in relation to water qualitative characteristics and environmental morphology were simultaneously and monthly sampled with 36 presence and 36 absence of individuals during one year study period (2017-2018). According to the results of the Mann-Whitney test, there was a significant difference between the presence and absence of A. cygnea and the most variables (p < 0.05 for orthophosphate and total suspended solids, and p < 0.01 for others). The only exception was for the variables of air and water temperature, of which there was no significant difference between the presence and absence of A. cygnea and the given variables (p > 0.05). Based on the results of generalized linear model (GLM), the increase in the values of water depth, flow velocity, water turbidity, electric conductivity, orthophosphate and nitrate may decrease the probability of presence occurrence of A. cygnea (p <0.01). While increase in dissolved oxygen concentration and total hardness may increase the probability of the presence of A. cygnea in the wetland (p < 0.01). Based on the results of generalized linear model, there was no any statistically significant difference between presence of absence of A. cygnea and water temperature.