ﺑﺮرﺳﯽ رﯾﺨﺖﺷﻨﺎﺧﺘﯽ و ﺑﺮﺧﯽ ﺧﺼﻮﺻﯿﺎت زﯾﺴﺘﯽ ﻻيﻣﺎﻫﯽ Tinca tinca (Linnaeus, 1758 در ﺗﺎﻻب اﻧﺰﻟﯽ

The study of morphometric and meriestic features of Tench (Tinca tinca) In Anzali lagoon

ﻻيﻣﺎﻫﯽ از ﮐﭙﻮرﻣﺎﻫﯿﺎن اﻗﺘﺼﺎدي ﻣﯽﺑﺎﺷﺪ ﮐﻪ در دﻫﻪ اﺧﯿﺮ ﻣﯿﺰان ﺻﯿﺪ آن در ﺗﺎﻻب اﻧﺰﻟﯽ ﺑﻪﺷﺪت ﮐﺎﻫﺶ ﯾﺎﻓﺘﻪ اﺳﺖ. ﻫﺪف از ﺑﺮرﺳﯽ ﮐﻨﻮﻧﯽ، ﻣﻄﺎﻟﻌﻪ ﺑﺮﺧﯽ ﺧﺼﻮﺻﯿﺎت زﯾﺴﺘﯽ اﯾﻦ ﻣﺎﻫﯽ در ﺗﺎﻻب اﻧﺰﻟﯽ ﺑﻮده و ﺑﺪﯾﻦ ﻣﻨﻈﻮر 96 ﻧﻤﻮﻧﻪ ﻣﺎﻫﯽ از ﺑﻬﻤﻦ 1385 ﺗﺎ ﺗﯿﺮﻣﺎه 1386 ﺑﺎ ﺗﻮر ﮔﻮﺷﮕﯿﺮ ﺻﯿﺪ ﺷﺪ. ﻃﺒﻖ ﯾﺎﻓﺘﻪﻫﺎي ﺣﺎﺿﺮ، 11 ﺗﺎ از 36 ﺻﻔﺖ رﯾﺨﺖﺳﻨﺠﯽ و ﯾﮑﯽ از 10 ﺻﻔﺖ ﺷﻤﺎرﺷﯽ ﺑﯿﻦ ﻧﺮ و ﻣﺎده اﺧﺘﻼف داﺷﺖ )p<0/05(. وزن ﺑﺪن 40/7 ﺗﺎ 3 /299 و ﻣﯿﺎﻧﮕﯿﻦ آن در ﻧﺮﻫﺎ و ﻣﺎده ﻫﺎ ﺑﻪﺗﺮﺗﯿﺐ 117/8±51/0 و 117/8±54/4 ﮔﺮم، ﻃﻮل ﭼﻨﮕﺎﻟﯽ 135/2 ﺗﺎ 255/7 و ﻣﯿﺎﻧﮕﯿﻦ آن در ﻧﺮﻫﺎ و ﻣﺎدهﻫﺎ ﺑﻪﺗﺮﺗﯿﺐ 182/0±27/7 و 181/9±23/6 ﻣﯿﻠﯽﻣﺘﺮ ﺗﻌﯿﯿﻦ ﺷﺪ و ﺗﻔﺎوﺗﯽ ﺑﯿﻦ ﻧﺮ و ﻣﺎده ﻣﺸﺎﻫﺪه ﻧﺸﺪ. ﺳﻦ ﻧﺮﻫﺎ ﺑﯿﻦ 2 ﺗﺎ 7 ﺳﺎل و ﻣﺎدهﻫﺎ ﺑﯿﻦ 2 ﺗﺎ 6 ﺳﺎل ﺑﻮده ﮐﻪ ﻣﺎﻫﯿﺎن 3 و 4 ﺳﺎﻟﻪ در ﻫﺮ دو ﺟﻨﺲ ﻏﺎﻟﺐ ﺑﻮدﻧﺪ. ﻧﺮﻫﺎ 46/9 و ﻣﺎدهﻫﺎ 53/1 درﺻﺪ ﺟﻤﻌﯿﺖ را ﺗﺸﮑﯿﻞ دادﻧﺪ ﮐﻪ ﺑﺎ ﻧﺴﺒﺖ اﺳﺘﺎﻧﺪارد )1ﻧﺮ:1ﻣﺎده( ﺗﻔﺎوت ﻣﻌﻨﯽدار ﻧﺪاﺷﺖ )p>0/05(. ﻫﻤﭽﻨﯿﻦ ﻣﻘﺪار ﺷﯿﺐ ﺧﻂ )b( رﮔﺮﺳﯿﻮن ﺑﯿﻦ وزن ﺑﺪن و ﻃﻮل ﭼﻨﮕﺎﻟﯽ ﻧﺮﻫﺎ و ﻣﺎدهﻫﺎ ﺑﻪﺗﺮﺗﯿﺐ 3/21 و 2/99 ﺑﻪدﺳﺖ آﻣﺪ و رﺷﺪ در ﻫﺮ دو ﺟﻨﺲ اﯾﺰوﻣﺘﺮﯾﮏ ﺑﻮد. ﻣﯿﺎﻧﮕﯿﻦ ﺿﺮﯾﺐ ﭼﺎﻗﯽ در ﻧﺮﻫﺎ 1/82±0/23 و ﻣﺎدهﻫﺎ 1/86±0/24 و ﺿﺮﯾﺐ ﭼﺎﻗﯽ ﻧﺴﺒﯽ ﻧﯿﺰ ﺑﻪﺗﺮﺗﯿﺐ 0/99±0/13 و ﻣﺎدهﻫﺎ 1/01±0/13 ﺗﻌﯿﯿﻦ ﺷﺪ ﮐﻪ ﻫﯿﭽﮑﺪام ﺑﯿﻦ دو ﺟﻨﺲ اﺧﺘﻼﻓﯽ ﻧﺪاﺷﺖ. ﻫﻢآوري ﻣﻄﻠﻖ در 24 ﻧﻤﻮﻧﻪ 14 ﺗﺎ 154 ﻫﺰار ﻋﺪد ﺗﺨﻢ و ﻫﻢ-آوري ﻧﺴﺒﯽ 170/1 ﺗﺎ 644/8 ﻋﺪد ﺗﺨﻢ در ازاي ﯾﮏ ﮔﺮم ﻣﺎﻫﯽ ﻣﺎده ﺑﺮآورد ﮔﺮدﯾﺪ. ﺑﻪﻃﻮرﮐﻠﯽ، ﺧﺼﻮﺻﯿﺎت ﻣﻮرﻓﻮﻣﺘﺮﯾﮏ و ﻣﺮﯾﺴﺘﯿﮏ ﻻيﻣﺎﻫﯽ ﺑﺎ ﻣﻨﺎﺑﻊ دﯾﮕﺮ ﺗﻔﺎوت ﻧﺎﭼﯿﺰي داﺷﺖ اﻣﺎ ﺧﺼﻮﺻﯿﺎت زﯾﺴﺖﺷﻨﺎﺧﺘﯽ ﻧﻈﯿﺮ ﻃﻮل، وزن، ﺳﻦ، ﻧﺴﺒﺖ ﺟﻨﺴﯽ، اﻟﮕﻮي رﺷﺪ و ﺿﺮﯾﺐ ﭼﺎﻗﯽ ﺑﺎ ﺑﺮﺧﯽ ﻣﻨﺎﺑﻊ ﻣﺘﻔﺎوت و ﺑﺎ ﺑﺮﺧﯽ ﻫﻤﺨﻮاﻧﯽ داﺷﺖ ﮐﻪ ﺑﻪﻧﻈﺮ ﻣﯽرﺳﺪ ﺗﻌﺪاد ﻧﻤﻮﻧﻪ، ﺷﺮاﯾﻂ ﻓﯿﺰﯾﻮﻟﻮژﯾﮏ، ﺗﺮﮐﯿﺐ ﺟﻨﺴﯽ، وﺿﻌﯿﺖ ﺗﻐﺬﯾﻪ و ﻋﻮاﻣﻞ دﯾﮕﺮ ﻣﺆﺛﺮ ﺑﺎﺷﻨﺪ.

Tench an economically important species in Anzali Lagoon has experienced a sharp catch decline in recent years. The present study aims at examining certain biological traits of the fish in Anzali lagoon. A sample of 96 pieces of such fish were netted out through gillnet fishing during Jan 2006-July 2007. The findings showed incongruity in 11 out of 36 morphometric traits followed by 1 out of 10 numerical traits among male and female fish (p ≤0.05). Body weight of the fish varied from 40.7 up to 299.3gr with the mean figures for male and female fish at 117.8±51.0 and 117.8±54.4gr respectively. Fork length ranged from 135.2 to 255.7 with the mean 182.o±27.7 and 181.9±23.6mm for male and female fish respectively, showing no difference between them .The male fish age ranged from 2 to 7 years and for the female ones, it was 2-6.yrs with the 3-4 years as the dominant age group in both sexes. The male constituted 46.9 % of the fish population followed by 53.1% of female ones showing no major difference with the standard (1:1) ratio(x 2=0.38). In addition, the gradient of the b regression line between the body weight and fork length of male and female fish were found to be 3.21 and 2.99 respectively with isometric growth in both sexes. The average condition factor in male fish was 1.82±0.23 and 1.86±0.24 in female with the recorded relative condition factor were 0.99±0.13 in male fish and 1.01±13 in female ones revealing no differences across sexes. Absolute fecundity of 24 sample fish varied between 14000 and 154000 with relative fecundity falling between 170.1 to 644.8 pieces of egg per each gram of female fish.