بررسی تغییرات بیوماس و صید به ازای سطح کفزیان براساس مساحت جاروب شده در آب های شمالی دریای عمان (استان سیستان و بلوچستان)

در این بررسی نیز منطقه مورد پژوهش  از مرز آبی ایران در غرب آغاز و تا مرز ایران و پاکستان در شرق دریای عمان بوده و کل منطقه مطالعاتی به 5 زیر منطقه m   تا q   در لایه های عمقی مختلف 20-10، 30-20، 50-30 و 100-50 متر تقسیم بندی شده است . . ﺑﺎﺗﻮﺟﻪ ﺑﻪ ﺗﻐﯿﯿﺮات ﻣﯿﺰان ﻣﯿﺎﻧﮕﯿﻦ ﺑﯿﻮﻣﺎس اﻋﻤﺎق ﻣﺨﺘﻠﻒ ﻣﯽ ﺗﻮان ﮔﻔﺖ ﻣﯿﺰان ﻣﯿﺎﻧﮕﯿﻦ ﺑﯿﻮﻣﺎس اﻋﻤﺎق ﮐﻤﺘﺮ از 20 ﻣﺘﺮﮐﺎﻫﺶ ﺑﯿﺸﺘﺮی داﺷﺘﻪ اﺳﺖ و ﻣﯿﺎﻧﮕﯿﻦ ﺑﯿﻮﻣﺎس ﮐﻒ زﯾﺎن دراﻋﻤﺎق ﮐﻤﺘﺮ از 20 ﻣﺘﺮ از ﻣﯿﺰان ﻧﺰدﯾﮏ 14 ﻫﺰار ﺗﻦ در ﺳﺎل 1382 ﺑﻪ ﺣﺪود 1/5 ﻫﺰار ﺗﻦ در ﺳﺎل 1400 ﮐﺎﻫﺶ ﻣﻌﻨﯽ داری ﯾﺎﻓﺘﻪ )0.05>p( و ﺗﺠﻤﻊ ﺑﯿﻮﻣﺎس ﮐﻒ زﯾﺎن از ﻣﻨﺎﻃﻖ ﺳﺎﺣﻠﯽ و ﮐﻢ ﻋﻤﻖ ﺑﻪ ﻣﻨﺎﻃﻖ ﻋﻤﯿﻖ ﺗﺮ ﻣﺘﻤﺎﯾﻞ ﮔﺸﺘﻪ اﺳﺖ. ﻫﻤﭽﻨﯿﻦ ﻣﯿﺰان ﻣﯿﺎﻧﮕﯿﻦ ﺻﯿﺪ ﺑﻪ ازای ﺳﻄﺢ )cpua( ﻣﻨﺎﻃﻖ ﻣﺨﺘﻠﻒ ﺳﺎل ﻫﺎی 1382 اﻟﯽ 1400 روﻧﺪ ﮐﺎﻫﺸﯽ داﺷﺘﻪ و ﻣﻌﻤﻮﻻً ﻣﻨﺎﻃﻖ c و e دارای ﻣﻘﺎدﯾﺮ ﺑﺎﻻﺗﺮی ﻧﺴﺒﺖ ﺑﻪ ﺳﺎﯾﺮ ﻣﻨﺎﻃﻖ در ﺳﺎل ﻫﺎی ﻣﺨﺘﻠﻒ ﺑﻮده اﻧﺪ )0.05 >p(. ﺑﺮﺧﯽ از ﮔﻮﻧﻪ ﻫﺎ از ﺟﻤﻠﻪ ﻣﺎﻫﯽ ﺷﻮرﯾﺪه، ﻣﺎﻫﯽ ﺷﻌﺮی، ﺳﻔﺮه ﻣﺎﻫﯿﺎن و ﮐﻮﺳﻪ ﻣﺎﻫﯿﺎن ﮐﺎﻫﺶ ﺷﺪﯾﺪی داﺷﺘﻪ و ﺑﺮﺧﯽ از ﮔﻮﻧﻪ ﻫﺎی آب زی از ﺟﻤﻠﻪ ﻣﺎﻫﯽ ﺳﻠﻄﺎن اﺑﺮاﻫﯿﻢ، ﻣﺎﻫﯽ ﺣﺴﻮن و ﻣﺎﻫﯽ ﮐﻮﺗﺮ در ﺗﺮﮐﯿﺐ ﺻﯿﺪ اﻓﺰاﯾﺶ ﻧﺸﺎن ﻣﯽ دﻫﺪ. ﻧﺘﺎﯾﺞ ﺣﺎﺻﻞ از ﻣﺪل آﻧﺎﻟﯿﺰ روﻧﺪ درﺟﻪ دو )3.70 =msd = 0.03 ،mad = 0.15 ،mape ( ﺑﻬﺘﺮ از ﺳﺎﯾﺮ ﻣﺪل ﻫﺎ ﺑﺮاﺳﺎس اﯾﻦ آزﻣﻮن ﻫﺎ و ﺿﺮاﯾﺐ ﺑﻬﺘﺮ ﺑﻮد و ﻣﺪل ﻫﺎ ﭘﯿﺶ ﺑﯿﻨﯽ ﺗﺮﮐﯿﺒﯽ ﻣﺨﺘﻠﻒ ارﯾﻤﺎ ))arima, (p , d, q( ﺑﺮاﺳﺎس ﺷﺎﺧﺺ aic اﻣﺘﺤﺎن ﺷﺪ و ارﯾﻤﺎ ﻣﺪل )1 و 1 و 0( ﺑﻬﺘﺮﯾﻦ ﺗﻨﺎﺳﺐ را ﺑﺎ روﻧﺪ ﺗﻐﯿﯿﺮات ارﯾﻤﺎ ﺑﯿﻮﻣﺎس ﮐﻒ زﯾﺎن ﺑﺮاﺳﺎس ﻣﺴﺎﺣﺖ ﺟﺎروب ﺷﺪه در آب ﻫﺎی ﺷﻤﺎﻟﯽ درﯾﺎی ﻋﻤﺎن )اﺳﺘﺎن ﺳﯿﺴﺘﺎن و ﺑﻠﻮﭼﺴﺘﺎن( داﺷﺖ. ﺑﻪ ﻃﻮرﮐﻠﯽ ﻣﯽ ﺗﻮان ﻧﺘﯿﺠﻪ ﮔﺮﻓﺖ ﮐﻪ ﺑﺎﺗﻮﺟﻪ ﺑﻪ ﺷﺮاﯾﻂ و وﺿﻌﯿﺖ اﺷﺎره ﺷﺪه، ﻣﯿﺰان ﺻﯿﺪ ﮐﻒ زﯾﺎن در وﺿﻌﯿﺖ ﻣﻨﺎﺳﺒﯽ ﻗﺮار ﻧﺪاﺷﺘﻪ و ﺑﺎﯾﺴﺘﯽ اﻗﺪاﻣﺎت ﻣﺪﯾﺮﯾﺘﯽ در ﺟﻬﺖ ﮐﺎﻫﺶ ﺻﯿﺪ اﯾﻦ آﺑﺰﯾﺎن ﺻﻮرت ﮔﯿﺮد.

investigation of biomass and catch per unite area changes of demersal resources based on swept area method in the northern waters of oman sea (sistan and baluchestan province)

for more than two decades, assessment and monitoring of oman sea demersal resources has been carried out using swept area method. the study area starts from western water of iran to border of iran and pakistan in the east of oman sea and total study area were divided into 5 sub-areas m to q in different depth layers of 10-20, 20-30, 30-50 and 50 -100 meters. in general, the average amount of biomass has a downward trend in different depths of 2003 to 2021 years. due to the changes in the average biomass at different depths, it can be said that the average biomass at depths of less than 20 meters has decreased. average biomass of depths less than 20 meters have decreased significantly from about 14 thousand tons in 2003 to about 1.5 thousand tons in 2021 (p<0.05), and benthic biomass accumulation has shifted from coastal and shallow areas to deeper areas. also, average catch per unit area of different areas had a decreasing trend in 2003 to 2021 and usually regions o and q had higher values than other regions in different years (p <0.05). some species fish such as otolitus ruber, lethrinidae, ray and sharks have decreased sharply and some species fish such as nemipterus japonicus, saurida tumbil and sphyraena sp. have increased in fishing composition. considering the mentioned conditions, it seems that the amount of demersal resources caught is not in a good condition and measures should be taken to reduce the catch of these fish.