پويايي شناسي جمعيت ماهي سفيد رودخانه اي (Linnaeus, 1758) Squalius cephalus در درياچه سد شهيد رجايي ساري، استان مازندران

Population dynamics of Squalius cephalus in Shahid Rajai Dam in Sari, Mazandaran Province

در اﯾﻦ ﺗﺤﻘﯿﻖ ﺑﺮﺧﯽ ﭘﺎراﻣﺘﺮﻫﺎي ﭘﻮﯾﺎﯾﯽﺷﻨﺎﺳﯽ ﺟﻤﻌﯿﺖ ﻣﺎﻫﯽ ﺳﻔﯿﺪ رودﺧﺎﻧﻪاي )S. cephalus( در درﯾﺎﭼﻪ ﺳﺪ ﺷﻬﯿﺪ رﺟﺎﯾﯽ ﺳﺎري ﻣﻮرد ﺑﺮرﺳﯽ ﻗﺮار ﮔﺮﻓﺖ. ﻧﻤﻮﻧﻪﺑﺮداري ﺑﻪﺻﻮرت ﻓﺼﻠﯽ و ﺑﻪﻣﺪت ﯾﮏﺳﺎل ﺑﻪوﺳﯿﻠﻪ ﺗﻮر ﮔﻮﺷﮕﯿﺮ ﺑﺎ ﭼﺸﻤﻪﻫﺎي 40 ،30 ،20 ،10 و 50 ﻣﯿﻠﯽﻣﺘﺮ )ﮔﺮه ﺗﺎ ﮔﺮه ﻣﺠﺎور( در 3 اﯾﺴﺘﮕﺎه اﻧﺠﺎم و ﻃﯽ اﯾﻦ ﻣﺪت ﺗﻌﺪاد 591 ﻧﻤﻮﻧﻪ ﺻﯿﺪ ﺷﺪ. ﺑﯿﺸﺘﺮﯾﻦ و ﮐﻤﺘﺮﯾﻦ ﻓﺮاواﻧﯽ ﺻﯿﺪ ﺑﻪﺗﺮﺗﯿﺐ 303 ﻧﻤﻮﻧﻪ در ﻓﺼﻞ ﭘﺎﯾﯿﺰ و 43 ﻧﻤﻮﻧﻪ در ﻓﺼﻞ زﻣﺴﺘﺎن ﺑﻮده اﺳﺖ. ﻧﻤﻮﻧﻪﻫﺎي ﺻﯿﺪ ﺷﺪه در 6 ﮔﺮوه ﺳﻨﯽ 0 ﺗﺎ 5 ﺳﺎﻟﻪ، ﮐﻪ ﮔﺮوه ﺳﻨﯽ 2 در ﻫﺮ دو ﺟﻨﺲ ﻧﺮ و ﻣﺎده داراي ﺑﯿﺸﺘﺮﯾﻦ ﻓﺮاواﻧﯽ ﺑﻮد. ﻧﺴﺒﺖ ﺟﻨﺴﯽ ﻣﺎده ﺑﻪ ﻧﺮ 1:1/06 ﺑﻪدﺳﺖ آﻣﺪ ﮐﻪ ﺑﺎ ﻧﺴﺒﺖ 1:1 اﺧﺘﻼف ﻣﻌﻨﯽداري ﻣﺸﺎﻫﺪه ﻧﺸﺪ. ﮐﻞ ﻣﺎﻫﯿﺎن ﺻﯿﺪ ﺷﺪه در ﻣﺤﺪوده 102 ﺗﺎ 265 ﻣﯿﻠﯽﻣﺘﺮ و ﻣﺤﺪوده وزﻧﯽ 11/59 ﺗﺎ 241/86 ﮔﺮم ﺑﻮدﻧﺪ. در ﮐﻞ ﺟﻤﻌﯿﺖ، اﻧﺪازه ﻃﻮﻟﯽ و وزﻧﯽ ﻣﺎدهﻫﺎ ﺑﻪﻃﻮر ﻣﻌﻨﯽداري ﺑﯿﺸﺘﺮ از ﻧﺮﻫﺎ ﺑﻮد. راﺑﻄﻪ طولي وزني براي ﻣﺎدهﻫﺎ، ﻧﺮﻫﺎ و در ﮐﻞ ﺟﻤﻌﯿﺖ ﺑﻪﺗﺮﺗﯿﺐ W=0.000001L3.01، 05 W=0.000001L و 3.01 W=0.000009L3.05 ﺑﻪدﺳﺖ آﻣﺪ. اﻟﮕﻮي رﺷﺪ ﺑﺎﺗﻮﺟﻪ ﺑﻪ ﻣﻘﺪار ﺷﯿﺐ ﺧﻂ رﮔﺮﺳﯿﻮﻧﯽ ﺑﯿﻦ ﻃﻮل و وزن و ﺑﺮاﺳﺎس ﻣﻌﺎدﻟﻪ رﺷﺪ ﭘﺎﺋﻮﻟﯽ، ﺑﺮاي ﻫﺮ دو ﺟﻨﺲ ﻧﺮ و ﻣﺎده و ﮐﻞ ﺟﻤﻌﯿﺖ اﯾﺰوﻣﺘﺮﯾﮏ ﻣﺤﺎﺳﺒﻪ ﺷﺪ. ﻣﻌﺎدﻟﻪ رﺷﺪ ﺑﺮﺗﺎﻻﻧﻔﯽ ﺑﺮاي ﺟﻨﺲ ﻧﺮ و ﻣﺎده ﺑﻪﺗﺮﺗﯿﺐ ﻣﺤﺎﺳﺒﻪ ﺷﺪ ﮐﻪ ﻣﻘﺪار ﻋﺪدي ﻃﻮل ﺑﯽﻧﻬﺎﯾﺖ در ﺟﻨﺲ ﻣﺎده ﺑﯿﺸﺘﺮ از ﻧﺮ ﺑﻮده اﺳﺖ. از ﻧﻈﺮ آﻣﺎري اﺧﺘﻼف ﻣﻌﻨﯽداري ﺑﯿﻦ ﻓﺎﮐﺘﻮر وﺿﻌﯿﺖ ﺟﻨﺲﻫﺎي ﻧﺮ و ﻣﺎده ﻣﺎﻫﯿﺎن ﺳﻔﯿﺪ رودﺧﺎﻧﻪاي در درﯾﺎﭼﻪ ﺳﺪ رﺟﺎﯾﯽ ﻣﺸﺎﻫﺪه ﺷﺪ. ﺑﺮرﺳﯽ ﻃﻮل ﻧﺴﺒﯽ روده در ﻫﻤﻪ ﮔﺮوه ﺳﻨﯽ ﻧﺸﺎن داده ﮐﻪ ﻣﺎﻫﯽ ﺳﻔﯿﺪ رودﺧﺎﻧﻪاي رژﯾﻢ ﻏﺬاﯾﯽ ﮔﻮﺷﺖﺧﻮاري دارد. ﻣﯿﺎﻧﮕﯿﻦ ﻫﻢآوري ﻣﻄﻠﻖ و ﻧﺴﺒﯽ ﻧﻤﻮﻧﻪﻫﺎي ﺑﺎﻟﻎ ﺟﻨﺲ ﻣﺎده ﺑﻪﺗﺮﺗﯿﺐ ﺑﺮاﺑﺮ )4478/2±75/6( و )54/1±65/6( ﺑﺮآورد ﺷﺪ. ﻣﯿﺎﻧﮕﯿﻦ ﻗﻄﺮ ﺗﺨﻤﮏ ﻣﺎﻫﯿﺎن در اﯾﻦ ﺗﺤﻘﯿﻖ )0/86 (±0/12 ﻣﯿﻠﯽﻣﺘﺮ ﺑﻪدﺳﺖ آﻣﺪ. ﻧﺘﺎﯾﺞ اﯾﻦ ﺗﺤﻘﯿﻖ در ﻣﻘﺎﯾﺴﻪ ﺑﺎ ﺟﻤﻌﯿﺖ رودﺧﺎﻧﻪ ﺗﺠﻦ ﻧﺸﺎن داد ﮐﻪ ﺑﺴﯿﺎري از ﭘﺎراﻣﺘﺮﻫﺎي زﯾﺴﺘﯽ اﯾﻦ ﮔﻮﻧﻪ در درﯾﺎﭼﻪ ﻧﺴﺒﺖ ﺑﻪ ﺟﻤﻌﯿﺖ رودﺧﺎﻧﻪ ﺗﺠﻦ وﺿﻌﯿﺖ ﻣﻄﻠﻮبﺗﺮي داﺷﺘﻨﺪ.

To study some population dynamic parameters of the Chub (S. cephalus) in the Shahid Rajaii Dam Lake, five hundred and ninety one fish were captured by gill nets (mesh size: 10, 20, 30, 40, and 50 mm) from three stations. The most frequent catch was in autumn (303) and the lowest was in winter (43). The captured fish were divided into six age groups, 0+ to 5+ years for both sexes and 2-year-olds were prevailing in both sexes. The sex ratio of female to male was 1:1.06. The length of animals ranged from 102 to 265 mm and the weight ranged from 11.59 to 241.86 g. In overall, the length and weight of the females were higher than males. The weight-length relationship was estimated as for females and for males, and for the population. Growth pattern, in all considered groups, was calculated isometric. The Von Bertalanffy growth equations for males and females were Lt=27.04(1-e-0.23(t+2.03)) and Lt=31.4(1-e-0.22(t+1.31)), respectively and the infinity length in females was higher than males. A significant difference was observed in the condition factor in both sexes. The relative length of the intestine showed a carnivorous diet for this species. The average absolute and relative fecundity were 4478.2±75.6 and 54.1±65.6, respectively. The average of female egg diameter was 0.86 ±0.12 mm. The comparison of results of this study with the Tajan River population show that many biological parameters of this species in the Shahid Rajaii Dam Lake were more favourable than those in the Tajan River.