بخشی از متن دانلود فایل word مقاله ارزیابی ذخایر تاسماهی ایرانی (Acipenser persicus) در حوضه جنوبی دریای خزر طی سال های 88-1387 :
تعداد صفحات :13
Species composition, relative abundance, absolute abundance and biomass of sturgeon species were studied during the years 2008-2009. Eighty five stations were covered in the stratified random sampling design in depths less than 1Om using 9m bottom trawl (head line) and in depths more than 10m using 24.7m bottom trawl (head line). More than 70 specimens of Acipenser persicus were caught during the effort. CPUE decreased from 0.4 to 0.24 specimens per trawl in 2009. The mean total length of the A. persicus was 47.3±29.lcm and 61.9±28.7cm in 2008 to 2009, respectively. The smallest size of A. persicus was 9cm in 2008 and 24.5cm in 2009, while the maximum size was I 02.5cm in 2008 and 126.5±29cm in 2009. The mean total weight in 2009 in comparison with 2008 increased from 989(3- 5000g) to 1569(42-71OOg). Absolute abundance of A. persicus decreased from 2006000 specimens in 2008 to 1192000 specimens in 2009. The estimated biomass was 2010 and 1878 tons in 2008 and 2009, respectively. According to the results of study, the stock status of A. persicus is highly critical in the Caspian Sea and a timely decision has to be taken for conservation of the species.